4/13/07 FCST: TX / OK / AR / MO / IL / TN

[Michael O'Keeffe]

The latest GFS shows a very strong low to eject out of the high plains into SE Kansas on Friday April 13th. Deep moisture and shear will contribute to very favorable conditions for possibly strong tornadic supercells across the S Plains into the Mid-Mississippi Valley. The area most at risk seems to be N TX/far E OK/most of MO/AR/W.KY/W.TN/W.IL

[Ray Walker]

This system continues to look more and more interesting. The system for tuesday looks weaker than earlier proged, which means the gulf should be primed for strong moisture advection into the southern plains. The stage looks to be set for a potentially dangerous severe weather episode across the eastern 2/3 to 1/2 of Oklahoma, most of north and central texas on east into Arkansas, louisiana, and parts of MO. The models are showing the main action to be across eastern portions of the area, however I dont think the dryline will make it as far east as the models are showing.

[Jim Bishop]

Friday looks like a big severe weather outbreak from Northeast Texas/Eastern Oklahoma to Arkansas and Missouri. Moisture return may have been an issue a couple days ago. But both the GFS & European models show a great return flow off the Gulf by Thursday.

[Chris C Sanner]

NWSFO OUN is still saying that the dryline won't be as far east as what the models are saying which I think will be the case. Remember March 28th? Up until the day of the event we were still looking at a dryline in the E. Texas Panhandle and the dryline ended up in the Western Texas Panhandle. The chaseability of the setup is a bit in question to me too as the storms could be hauling in less than favorable chase terrain. If things verify though "somewhere" across the plains then that area looks to have a pretty long day ahead of it in terms of severe weather.

[Brian Stertz]

Depending on which model one buys in to...Friday should be a pretty active and potentially significant severe wx day. The Euro tracks a surface low out of EC/SE Oklahoma into N. Arkansas during the day. It appears that the shear should be good to excellent for some strong and possibly intense tornadic supercells, particularly across N/C Arkansas along the warm front and vicinity of the surface low. It looks like mid 60 Td's will be in place along/north of the warm front, with upper 60's and possibly even lower 70 Td's across N. Louisiana, S.Arkansas, and W/S Mississippi. Now all that remains a quandry is timing of the wave(s). Also, will have to see if N.Texas/SE Oklahoma may also be a play on the dryline. Not too excited to see all the veered low level winds there, but if timing is slower, this may also be an area to keep an eye on.

[Brandon Sullivan]

Im buying into this system... I like the tilt of the low.. Looks stronger and stronger each run.. Really thought the 4-8 would be further north, but it doesnt matter.. I really like the system.. Hope I get the new laptop before then!

[SteveCarter]

I'm starting to buy into this now as well. Had a day there where it seemed like the mositure would never make it up there, but it DOES appear it will. This has the potential to be a big event. We're ending up with to many threads dealing with the same storm, and same areas tho. Thinking maybe we need to add AL/MS/KY into this. What days will it be? Friday, maybe even Saturday into Sunday before it's all over.

[Brandon Sullivan]

Ya, we do have lots of threads.. A quick look at the 12z GFS, stille shows a nice setup.. Shear is looking pretty impressive with this system, aong with CAPE of around 1700 J/KG area wide.. Even with the further south track, nearly the entire area is "warm sectored" due to the negative tilt... I wont even try to get too specific with a target until wed.. when we have SWODY 3

[matt patterson]

Wow....The GFS is really kicking this system out very quickly as compared to previous runs... while the EC is lagging behind..... If the current run were to verify then i think one could write all of ok/ks/tx out of the mix. The NCEP says that they prefer the EC in their diagnostic discussion released at 1:20 CDT today....

I hope the models will have a better hold on things one way or another in the next 24 to 36 hrs......

[Jim Bishop]

Well the EC is more concistent compared to the GFS, so maybe that's why NCEP preferes it. It is interesting that the GFS has a more northern track with the low than the EC. In the past I've seen the EC have the further north track in most cases, and usually the verification is somehwere in-between, but closer to the EC solution.

In any case I do hope the EC is correct, because it would give me a much better chance of chasing given the more southern storm track and slower ejection of the trough.

[Brett Adair]

Looking like a big time, long lived severe weather outbreak to come. Excessive instability and gulf moisture looks to come back into the picture with a strong upper level system coming across the midwest. This looks to set the stage for a diffluent pattern across the southern plains/Gulf coast into the midsouth for an outbreak of severe storms Friday through Sunday.

[Kevin Crawmer]

After a brief look at the ECMWF and GFS I believe the best area at the moment looks to be in SE KS and southern MO. Dewpoints look to soar to around 60 as far north as Columbia, MO to St. Louis to around Springfield, IL into norhtern KY. The center of the low looks to be somewhere in central KS or at the MO/KS stateline at 00z Sat. Given the varying speeds of the models, an exact location will be tough to pick until 24 hrs out or less. I have a hunch that the models may continue to trend north putting the bullseye on NE OK, SE KS into the ozarks and points southward. It will be interesting to see if the surging dewpoints play out....I would love to be able to see some action up my way (St. Louis area)...I'm always up for a post-work chase.

[Travis Carlson]

I agree with the models possibly pushing the track of this system farther north in the upcoming runs. This is usually the case for developing mid-latitude systems in April. Current model guidance is taking the track through central Illinois or a little south of there. Also I believe the system may trend to slow down. We'll have to keep this in mind as well. We get a better update tomorrow, but all in all looks like a severe wx outbreak either way you cut it with a north or south track. I would not be surprised to actually see some decent snow totals as well in MN or WI out of this especially with a farther north track and if enough cold air is in place as well. Also have to keep an eye on that as well. Looks like an impressive system either way with a variety of weather for sure. Maybe another weekend chase?:cool:

[Brandon Sullivan]

Just took a look at the 18Z gfs.. It has the system south again.. .. With the main CAPE and QPF over SW MO and TX OK... New 00z WRF out soon..


EDIT: 00z WRF shows a still southern track, and not so much of a negative tilt.. Im still interested though.. Hopefully SWODY 4-8 will tell more tommorow!

[Gabe Garfield]

The 00Z NAM is showing a slower wave than the 12Z GFS had progged. If this trend continues (which, given the usual GFS bias, it probably will), I would expect the I35 corridor could become a potential play.

For comparison:
12Z GFS http://weather.ou.edu/~garfield/images/gfs12z.gif

00Z NAM http://weather.ou.edu/~garfield/images/nam00z.gif

EDIT:
It looks like the 00Z GFS continues with a fairly progressive wave (contrary to the 00Z NAM sol'n). Also, looks like the GFS is a bit more bullish with Tds on Thursday than the NAM.

Gabe

[SteveCarter]

Hate to copy and paste, but... MEMPHIS, TN........A STRONG LOW PRESSURE SYSTEM WILL DEVELOP ACROSS THE GREAT PLAINS
AND BEGIN PUSHING TOWARDS THE MIDSOUTH FRIDAY NIGHT. THIS SYSTEM
CONTINUES TO LOOK STRONG WITH THE INCREASING POSSIBILITY OF
BRINGING STRONG TO SEVERE THUNDERSTORMS TO THE AREA. THIS SYSTEM
WILL DEFINITELY BE SOMETHING TO KEEP AN EYE ON FOR FUTURE
FORECASTS. end paste.

Other forecasts from that area to Birmingham are saying about the same thing. Southern states may be in for more than previously thought. Thinking about going to the AL/MS/TN line Sat early. Still....a ways to go yet, and I'm sure a lot of fine-tuning will take place.

[Bill Tabor]

Wow, looks like big dynamics are coming to play. Could be some really fast storm motions judging by the 850mb and 500mb projected speeds. I much prefer the current NAM solution which is slower and further west and south by a bit. The GFS veered 850's aren't too impressive. I'll be looking for this system to slow and back up a bit more in the NAM solution - hopefully. Obviously a potential big tornado day if the sfc to 850mb can back. There will likely be some tornadoes regardless.

I'll not try and pin down a general area yet as it is still only Monday and not ready to play musical models quite yet.

[Simon Brewer]

WOW, this 'possible event' is still 3 days away, but it looks like a huge severe weather outbreak for Texas all the way up though Missouri and maybe southern Iowa or parts of Illinois! The forecast at all levels by the GFS and European are pointing for a very big tornado event!

[Ray Walker]

ya this event looks pretty conductive for a significant tornado outbreak. Tx, Ok, SE Ks, Mo, Ar, and Louisiana had better be on gaurd. If enough instability can develop then major tornadoes are likely in these areas Thursday through Friday night.

[Alex Lamers]

Just looking at the basics behind all the long range models it would seem that some locations are on tap for a pretty substantial severe weather event. The poleward extent and greatest severe threat remains much in doubt though as the model spread is still quite high. Take for instance the 10/00z GFS and 10/00z UKMET runs. The UKMET only develops weak cyclogenesis and keeps the low on a very southern track (N TX to SE TN), while the GFS takes a much stronger low and ejects it northeast (OK Pnhdl to NW IN).

Taking a look at the cyclone as it evolves over the Southern Rockies and Southern Plains in the vertical sense, it should be negatively tilted which would favor stronger/continued cyclogenesis. This tends to make me lean towards a track north of what the UKMET is depicting, as well as a stronger, more dynamic low accompanied by stronger forcing along frontal boundaries. As the mid trop low transitions past the Four Corners region, the jet streak aloft will be rounding the base of the trough and this should begin the northeastward ejection of the low pressure system. PVA maximum and best upper level difluence/favorable jet circulations favor cyclogenesis roughly in the N TX Pnhdl to OK Pnhdl region based on an eyeballed mean of model solutions. Basically this is a bunch of posturing but I see a surface low track somewhere from KGAG (Gage, OK) to KSTL (St. Louis, MO). I doubt the low will eject as steeply as the GFS is indicating but the low should be much stronger than the new UKMET shows.

Obviously I would expect the best severe weather threat to exist along and south of the line I just mentioned (KGAG to KSTL). By early afternoon the low should be roughly halfway along the KS/OK border area, probably somewhere near KICT (Wichita, KS). Dryline will trail to the south-southwest with a warm front arcing through SE KS into C/SE MO and then sloping southeastward into the TN Valley. It always seems like the dryline winds up further west than long range models depict it 2-5 days out. So, the severe weather threat could probably extend a bit further west than what I'm thinking right now. However I would expect fairly rapid development by mid afternoon south along the dryline from the low which would then spread quickly east-northeast into the Ozarks/Arklatex in the evening and to the Mississippi River in the overnight. So in summary......

Threat Region: SE KS, C/S MO, Far SW IL, all but SE AR, C/E OK, N LA, NE TX.
Approximate Timing: Fast initiation from 1-3pm CDT along the dryline and close to the surface low along the warm front. Best severe weather threat 3-9pm CDT. Waning intensity 9-11pm CDT.
Primary Threats:
First 4 hours: Supercells with primarily a large hail threat. In areas without a full day of diabatic heating to mix the boundary layer and veer surface winds, tornadoes will also probably be a threat with favorable directional shear. This would probably occur close to the surface warm front and the nose of the LLJ where the isentropic ascent and moisture advection would favor cloudier skies and showers initially.
Next 4 hours: Supercells will coalesce into multicell clusters which will ultimately likely form a quasi-linear system that will then march eastward with an increasing straight-line wind threat, as well as an attendant hail threat. Given mean flow isn't entirely normal to the initiating boundary, I would think the lines would be more segmented. Tornadoes would remain possible with isolated cells or supercells embedded in line segments. The low pressure system should be wrapped in fairly strong winds even in the low-levels (850 mb winds AOA 50 kts). Thus, it wouldn't be crazy to imagine a fairly widespread wind damage threat if sufficient heating occurs ahead of the developing storms.
Remainder of the event: Severe weather threat would decrease with the linear system falling victim to nocturnal cooling. Probably marginally severe wind/hail would be the threat...with the highest risk of severe weather transitioning to the south where instability would be higher and the effective inflow layer would be closer to the surface.Well thats my initial 2 cents. If it all falls together like most models are depicting (and not like the new UKMET), I would imagine there would be some tornadoes on Friday. It seems like a pretty classic setup...but I'm not entirely sure I'll be able to chase (3 tests and a quiz on Friday :mad:, but I am done by 1:30).

AJL

[Jim Bishop]

Holly crap, Friday still look huge from Eastern Texas up to Missouri. As of right now this setup screams tornadoes. It's just going to come down to location.

European is a bit slower and further south than GFS. Gabe already mention how the WRF was slower than the GFS yesterday. Maybe that trend is valid given the slower European solution? We shall see.

Another thing I wanted to point out is the SPC wording. In the relatively short period of time they've had the 4-8 day outlook available, I'm not sure I've ever seen 1)such a detailed discussion for an event, and 2) stated "the possibility of significant supercells with tornadoes". I couldn't agree more with that, just found it interesting.

[matt patterson]

Not to rehash on anything already noted above, but the 6z GFS is once again being progressive with the system sliding the low into sw mo by 00z.. However the NCEP model discussion still favors the EC due to consistancy and its "middle of the road" solution.... I still think that C/E OK, SE KS, and down into the lonestar state is the place to be on FRIDAY afternoon.... I bet we see the GFS slow down in the next 2 runs as the system will be coming on shore..

http://www.hpc.ncep.noaa.gov/discussions/pmdhmd.html

[V. Gensini]

Im not getting to excited until this system moves onshore. 00z gfs and 12z gfs have weakend the system considerably, not to mention bringing the system further south. I guess we will have to wait to see ;)

[SteveCarter]

Don't think I would pay to much attention to Iowa/IL/IN areas. This really seems to be taking a more southern turn. AR/TN/LA/eOK/ into MS/AL/cTN by Saturday, and finally sGA/FL by sunday? Even Carolinas Sunday? This is definately going to be a good potent sysytem.. The worry about moisture seems none existent now. A LOT of fine tuning to follow tho. And with it on a weekend......glad it IS going to be over such a large area...lol

[Brian Stertz]

Further inspection OF THE 12Z ETA...

The 995mb surface low forecast position looks to be centered near Medford OK by 00z Friday night. The 0-3km helicity is maximized across NC Oklahoma in vicinity of the warm front which is forecasted to stretch west to east just south of the OK-KS stateline. The forecasted 00z dryline position is located along a line from Enid to the OKC Metro to the west side of Ft. Worth TX. Things look very interesting for tornadic supercells...a few of which will be strong/intense with "stinger tail" type structures.


Looks like the 12z ETA was in strong suggestion that Friday's big-top event would be focused along/east of the I-35 corridor from N.Oklahoma southward into NC/NE Texas. The 0-3km CAPE forecast is solid ahead of the dryline and the shear is looking good. The storm motions were pretty rapid given the strong mid-level wind field of 50+ kts. over a large area. This may change if the supercells can get a slight eastward movement. Looks like the best forecasted combo of shear & instability should favor from SC/SE Oklahoma and NC/NE Texas if the 12z ETA pans out.

Certainly a solid MDT risk on tap for Friday if forecast holds true. Now comes the time to fine tune the target zone for the chase as the model updates warrant. :cool: All I have to say is that Oklahoma has been due for some significant severe wx, and this looks quite likely with this storm.

[matt patterson]

WOW!!!!!! the 00z nam really pushed the sfc low farther to the south... The 00z solution tonight would create a very difficult chase in terms of terrain... We will have to see if the future solutions bring back the futher north track...

[Dal Archer]

Aaaggghhhh! I agree Matt. Things are looking less favorable if the NAM pans out. The current solution could force things into SE OK/NE TX which certainly screws things up as far as chasing is concerned. I do not look forward to trying to navigate in the mountains of SE OK.

I am really hoping that things stay closer to the GFS solution. I will be interested to get a look at the next run of the GFS and also take another look at the next update on the NAM. This setup looks so good and I would hate to see things get messed up by pushing things too far to the south into unfavorable terrain.

Oh well, we still have some time and hopefully further runs will look much better.

[Fred Gossage]

00Z NAM shows the potential for a significant nocturnal tornado event across Arkansas and Lousiana, spreading across Mississippi and into Alabama Friday night and Saturday morning. Forecast soundings from the 00Z NAM show over 1000 j/kg CAPE with over 450 SRH, coupled with 67-69 F dewpoints and near 70 F temps over the Tuscaloosa/Centreville/Birmingham, Alabama area at 7:00 am CDT Saturday.

[Chris Wilburn]

I just noticed the same thing Matt. Also, nice dewpoints barely even make it into the extreme southcentral/southeastern Oklahoma area. The 00z NAM also weakens the surface low to 1000mb and is forecasted to be on the OK/TX border along the I-35 corridor at 00z. Still looks like a very nice system, esp. as mid 60 td's are now forecasted for northcentral Texas and central Texas. I should point out that parts of very extreme southcentral and southeastern Oklahoma td's are forecasted from low 60's to even a narrow band of mid 60's possible. Maybe things will change but for me personally I don't like the southern forecast of the surface low and hope it changes over the next couple days. However, for chasers in northcentral Texas and central Texas they may be in for a real treat. Like Matt pointed out above storms will not be in very favorable chasing terrain if things remain the way they are. I like many others am not a big fan of chasing the jungle of southeast Oklahoma. I have never chase northeast Texas, but I haven't heard too many good things in regards to chase terrain down there. If I had to pick an area now it would be just along the I-35 corridor in northcentral Texas where td's should be low to mid 60's and CAPE is forecasted near 2,000 J/kg. Maybe a westward shift of the low/dryline will occur in the next couple days and we can get away from areas of poor chase terrain. Still a few days out, but those are my thoughts at this time.

[Mikey Gribble]

NORTHERN HALF OF TEXAS
I'm not impressed with the 00Z run of the NAM. I think you would have the possibility of maybe a couple tornadoes, but I don't think about tornadoes when I see this kind of setup. Deep layer shear and instability are more than adequate for supercells, but the tornado potential just isn't there IMO if the 00Z NAM is to be believed.
You have overnight convection and cloud cover over the northern part of the warm sector. It does show temperatures rebounding a bit, but not as much as you would like to see. LCL's would be plenty low. Directional shear sucks and helicity continues to decrease throughout the afternoon as the stronger low level flow moves off to the East. The better low level shear is too far out over the warm sector. Storm motions are fast, but doable, so I wouldn't be too concerned about that (I always think the cutoff for being chaseable is around 35kts). Unless I lived close by, I wouldn't chase the northern half of Texas target. It definitely isn't worth the drive from ICT considering it's only the begining of April.

SOUTHERN HALF OF TEXAS
I do think you have a shot at a couple tornadoes down in the Houston to Lufkin area and directly East of there. CAPE is better, but deep layer shear is weaker (still good enough for supercells), but it becomes quite strong by 00Z as the mid-level jet moves into Texas. Low level shear is sufficient for tornadoes at 18Z, but helicity weakens to <200m2/s2 in Texas by 00Z as the stronger low level flow shifts East. So long as storms fire early and work there way out into the warm sector (into the better low level shear) I think there will be a window for tornadoes before storms outrun the instability axis.
DISCLAIMER - I looked at the 00Z run for less than 20 minutes and I haven't been following previous runs closely, so I could definitely be overlooking some things. This was just my first impression.

[mark plate]

I certainly expect the south solution to be correct. The ECMWF/UKMET have been consistent with this for several runs and now the NAM/WRF has jumped aboard. When the ECMWF and UKMET agree on something far different than the GFS, they are almost always the way to go. Assuming these southern models are correct, significant surface based storms will not be too far north into Oklahoma. In fact, the new NAM/WRF suggests snow is more likely in Oklahoma than tornadoes, with heavy snow just to the north in southern Kansas. I expect temps Friday to be very similar to today here in northeast Oklahoma...struggling to warm above the low-mid 50s. This looks like an ARKLATEX chase and mainly after dark.

[Jeff Snyder]

So... painful... to ... look... at...
The 0z NAM initialized the big 500mb low near the southwestern Great Lakes region a little farther southwest than previous forecasts suggested. The mid-level jet stream is now forecast to remain ~100mi further south than previous forecasts indicated through Wednesday. I assume this is a result of the cold front current traversing Oklahoma and Texas being a little stronger than earlier forecast, which allows the front to move a little farther south into the northern Gulf of Mexico through Wednesday (thermal wind relation tells us that a southward shift in the baroclinic boundary would also lead to a southward shift in the mid- and upper-level jet, which is what we see). With slightly weaker ridging downstream of the Thurs-Friday system, it seems that return flow is also impeded (with terrible Td forecast for Thursday, at least in terms of tornadic supercells across the southern Plains).

The 00z GFS also forecasts a very elongated 850mb low to develop across Oklahoma and Arkansas Friday. This acts to veer strongly the 850mb flow, also shifting the axis of the LLJ well east of the dryline / front. Oy!

Personally, the area in southcentral OK ahead of the SFC low looks best to me. Shear vectors are forecast to be out of the southwest, so the most 'normal' / perpendicular orientation of the dryline relative to this shear vector appears to be along the apparent dryline bulge to the east and southeast of the SFC low (the position of which has just shifted southward ~150 miles from the 12z NAM run). Man, I can't believe how different the 2m and QPF fields look on the 00z NAM compared to the earlier 12z run. The 00z GFS is even farther south than the NAM in terms of the sfc low position. I'm very hesitant about a chase in the jungles near dark with 50+kt storm motions.

FWIW, the area of northcentral Texas west of Paris is pretty good chase territory. If something develops near or west of I35 down near Fort Worth by afternoon, the logistics of the terrain and road network may provide for a chase that wouldn't be terribly difficult. I'm terribly, terribly disappointed in the turn of events. But hey, it can't get any worse, can it?

Edit: It is worth noting that both the NAM and GFS are faster than the ECMWF and UKMET (at least the 12z/10 runs). I'm not too impressed with the run-to-run consistency of either of the primary NCEP models in this case, and, as the HPC suggests, the ECMWF may be a more likely solution.

[Jason A.C. Brock]

Never utter the words "It cant get any worse than this". Life will take the oppurtunity to prove you wrong every time. I have been worrying about this system being in the jungles since the weekend and it looks like it may very well still do that. We are jsut gonna have to do what we do everytime. Wait till the morning of and make a choice. BTW. The more you tell yourself "its still early in the season" the next thing you know its Late May and your wondering where the hell all the tornadoes are.
Ill be hoping for things to setup close to the I-35 corridor from OKC to Fort Worth and then just go where the storms lead until dark.

[Brian Stertz]

I am still on board with Friday's chase potential, particularly in vicinity of the triple point which should be near Gainesville TX at 00z. Backed surface winds should be in place along the Red River east of I-35...along and just north of the warm front...with the classic thermal ridge poke aimed between Durant OK and Paris TX. STP and sig. severe forecast parameters are very high across SC/SE Oklahoma and this is where the strongest 0-1km shear is forecasted along/north of the warm front boundary. This is all based off the 00z ETA run. Chances are that with this being a powerhouse system, the actual triple point position and theta ridge Friday afternoon may be further back west towards the Wichita Falls TX area...at least that's my speculation. At any rate...still a "green light go" for a chase Friday. Also, one more thing of note, there is a pretty high potential of some strong-intense tornadic supercells in C/SC/SE Arkansas...N/W Mississippi & possibly extreme N.Louisiana after midnight. The low-mid level jet criss cross is maximized in these areas with a strong surge of deep Gulf moisture indicated ahead of the approaching surface low moving due east across the Arklatex. This could mean quite a bit of trouble for some dangerous late night Lower MS Valley tornadoes...particularly along the boundary from SC Arkansas into NW Mississippi.

[matt patterson]

Wow... What a turn of events!!!!!! Anywho, the 6z wrf places the sfc low right on the red river at or near I-35 by 00z on Friday... Also to note that it has the 500mb winds farther south than the previous run as well.... Im still hoping for some northward progression of the system but it is looking less and less like that will happen... To make matters worse there is nothing (severe weather wise) in the forseable future as the GOM will take a very hard hit, but that is for another thread... I will still attempt to chase this system because i could not imagine going all april without a stormchase..... Start praying to the weather gods......

[Brandon Sullivan]

south south south.. i think im out boys... have fun with it.

[Jim Bishop]

I guess most of the pessimism on this boards is do to the crappier chase terrain. I'll give you that, but the setup still looks very good for tornadic supercells. I'm a little surprised the SPC doesn't at least have a hatched area outlined. Actually I expected them to have a moderate risk, but I suppose they are being caution at this stage in the game.

At any rate the shear, moisture and instability will all be strong. Everything's just been shifted further south and west. Living in Houston this is actually really helpful for me. Gives me a chance to leave work early, gun it up I-45 and catch a supercell.

[Kenny Drake]

I guess most of the pessimism on this boards is do to the crappier chase terrain. I'll give you that, but the setup still looks very good for tornadic supercells. I'm a little surprised the SPC doesn't at least have a hatched area outlined. Actually I expected them to have a moderate risk, but I suppose they are being caution at this stage in the game.

At any rate the shear, moisture and instability will all be strong. Everything's just been shifted further south and west. Living in Houston this is actually really helpful for me. Gives me a chance to leave work early, gun it up I-45 and catch a supercell.

With the models currently jumping around (which I think they will have come to a consensus by tonights run) the SPC will not center in on an area. I would definitely expect a slight risk to go up by tomorrow morning's 2nd day outlook based on tonights model runs if they are tending towards a consensus.

[mark plate]

I may be wrong on this, but if I understand correctly, the highest risk allowed in day 3 is a slight, and no hatched areas are ever indicated on day 3.

[matt patterson]

They can issue MOD risks on day three... they did this on June 12 or 13 of 2005 i believe out in the texas panhandle.... Anyway, the 12z WRF/NAM is out and it looks like it has backed it up to the west a bit.. I-35 seems like a pretty good starting point if i were to pick a Western extent at this time... I think the triple point will be the place to be in either case where the shear is maximized along the WF... Personally i would rather the solution stay like it is now as opposed to 100 miles north, which will keep us out of the Jungle in SE OK.. If im correct the area south of the Red River E of 35 is not bad chase country?

[mark plate]

I stand corrected...a moderate CAN be issued on day 3, but according to this below, it never has been done. Since I have seen MANY situations much more volatile and certain than Friday in the past and it has never been done, I certainly would have been shocked to have seen it used for the first time for this system. A Day 2 HIGH has only been issued once before apparently...see the details below.

As far as Friday goes, yes the WRF/NAM has the surface low back to the west, but closer inspection shows the better parameters for significant severe well off to the southeast...in far eastern TX, LA, and far SW AR.

__________________________________________________ ______________

Day 2 outlooks, issued twice daily at 08Z and 1730Z, refer to tomorrow's weather (12Z-12Z of the next calendar day) and include only a categorical outline, textual description, and a probability graph for severe convective storms generally. Day 2 MDT risks are uncommon (only several times a year on average), and a Day 2 HIGH risk has only been issued once (for April 7, 2006).
Day 3 outlooks refer to the day after tomorrow, and include the same "break outs" as the Day 2 outlook. Higher probability forecasts are less and less likely as the forecast period increases due to lessening forecast ability farther in advance. No attempt is made to forecast general thunderstorms and a HIGH risk is never issued. While a MDT can be issued for Day 3, there are no known occurrences of such.

[Mikey Gribble]

I think the 12Z NAM makes northern Texas look quite a bit better. For one, temperatures recover better, warming into the mid to upper 70's. Moisture is slightly better as well. And most importantly to me, 850mb flow isn't veering as much as it was in the 00Z and the LLJ isn't as far away from the dryline as it was, which kicks low level flow up a bit. As a result, storms forming near the triple point (and slightly South along the dryline) could realize 0-3km helicity AOA 300m2/s2.
One thing that worries me is how narrow the window of insolation is in this target area. Temps are going to have to jump 10 degrees from 18Z to 00Z. There is a good dry punch wrapping in over the warm sector at 18Z, but I am still a little skeptical. I have changed my mind on whether or not I would chase though. I still will wait until tomorrow night to make the call, but if the 12Z NAM were to verify, I would target about 50 miles SE of the triple point and get on the first storm that had undisturbed inflow and I think it would have a pretty good shot at a tornado or two.
Storm motions of 45kts is not good for me. I already got two speeding tickets this season and apparently if you live in Kansas, number three gets your license taken away for a year. I wish I would have known that before and I would have rationed myself. If you see a black Xterra pulled over, please take one for the team and start swirving and speeding as you go by.

[Brian Stertz]

The 12z ETA shows a very well focused triple point over NC Texas by 00z Friday...it appears the strongest tornado parameters (steep lapse rates, good 0-3km VGP, lowered LCL's, decent inflow, 0-3km CAPE of 150-200 j/kg. to name a few) are in the Paris TX area. Just need to be sure that if a supercell initiates in the warm sector - triple point area that it will not immediately race northeast and over into the cold side of the boundary. If there can be that one rogue supercell or two that can ride eastward along the boundary (where obviously SRH and moisture pooling will be significant) then there may be that excellent chase where you can basically follow it along US-82 as it tracks eastward south of the Red River and ahead of the surface low. This is all speculating a forecast which the 12z ETA suggests. I like the decent focus presented in this new 12z ETA update, but storm motion trajectory will make or break this setup for Friday as it appears. Certainly do see a cause for concern overnight Friday into Sat. morning as things shift eastward into the Mississippi Delta area...for potentially some damaging tornadoes as deep moisture pools on the east-west boundary where 400-500 m2/s2 SRH is forecasted. Could be a wild and wooly night Friday night in this area as things shift eastward.

[Alex Lamers]

Well this forecast is just insanely complex. There are about as many very different solutions as there are numerical weather models. I had thought that the low would track from near KGUY to KSTL previously and it appears that the NAM and GFS have latched onto the southern track, barely skirting the Red River region with the surface low. Then again NGM and CMC follow my previous thinking. Most consistent solutions have been the ECMWF and UKMET which are projecting a more southern track. I still can't bring myself to think that the surface low will miss OK entirely and track south of the Red River. For now my model of choice is the 09z SREF with the mesoscale features displaced perhaps 25-50 miles north.

Given that the energy is still offshore and the models are jumpy, I don't think I'm going to try and make another detailed forecast but the setup with whichever model you use seems to echo a Miller Type A severe weather event with a Type I air mass (I'm using the 1972 Technical Report). This combo is good for tornado outbreaks. Applying what he outlined for the typical region for the highest severe weather concentration to the 09z SREF shifted just north, I would anticipate the best risk of severe weather to be south of a line from the Turner Falls/Arbuckles region in OK just north of Ardmore to near Clinton AR (NC AR) to just north of Memphis TN. It would also likely be north of a line from Waco TX to Vicksburg MS. In effect it encompasses SE OK, most of AR, N LA, NE TX. A secondary outbreak region would be possible from College Station TX to points about 100 miles south (near Wharton TX) and then east-northeastward into WC/C LA.

There are still a lot of question marks. However near the warm front in the primary outbreak region where the effective inflow layer will lower to near the surface, but overlap a region of backed surface flow and large, clockwise curved hodographs, there should be a pretty substantial tornado threat. 0-1km SRH in this region will likely exceed 300 m2/s2. Significant Tornado Parameter and Supercell Composite Parameters both look good as well. According to the Miller description, explosive storm development would likely occur in irregular clusters along the frontal boundary and leading edge of the mid-level dry air intrusion. These would be comprised of embedded supercells with the threat of very large hail and tornadoes.

The thing I'm concerned about is, with Type I air masses you typically see a lot of morning stratus over the threat region. The question is whether or not these will break up enough to allow heating and thus instability to build. The NAM does seem rather pessimistic about breaking up the cloud deck so we could wind up seeing a marginalized tornado threat and awful chase conditions with terrain and low clouds. Who knows? Tomorrow's 12z and 18z runs should start converging on a common solution as the wave offshore finally reaches the Pacific Coast.

AJL

[Brian Stertz]

If 18z MesoEta...the big supercells on Friday are shown to pop in the area between Paris and Tyler TX...this seems to be a LLJ convergence area where southwest winds are hitting south winds...edge of cap...and in the area along the warm front which extends from NE Texas into SW Arkansas. Looks like tough chasing in the Arklatex if this holds true. The MesoEta does pop more isolated cells back west on the dryline from near Sherman down to the southwest of Ft. Worth...not sure if the shear will be sufficent to support tornadoes or not because the LLJ axis has shifted into the Arklatex. Just will have to keep monitoring things as Alex mentioned in his very good post.

[Ray Walker]

Well first off I just want to say that the SPC has issued a day three MODERATE risk before. It didnt really verify in the target area, it was June-12-05 I beleive. They had a moderate risk up for the eastern texas panhand and western oklahoma down into the texas south plains. However as we all know the south plains had a nice localized tornado outbreak that day, but anyways back on subject.
This system is really complicating things for me. I live in SC Oklahoma so Location isnt an issue here. But I really would like to see the moisture much deeper and the storm track further to the north and west. Even though I do think north texas and southern Oklahoma WILL see tornadoes I dont know how widespread or significant they will be, or how chaseable these storms will be. Cape values around 1200j/k and extremely powerfull wind feilds may not be a good combination, and yet if very well might given the extreme dynamics and lift with this system. But Honestly in an environment such as this one I have seen that not enough cape and to much in the way of wind shear causes the towers to be ripped apart. Also this system may generate to many storms all at once. However If Isolated storms form or even a cluster of storms can form and ride along the warm front and establish good inflow then We should be all set. This storm just represents to many quetions right now for me. I will make a choice on whether I will go or not sometime tomarrow.

[Jeff Snyder]

If 18z MesoEta...the big supercells on Friday are shown to pop in the area between Paris and Tyler TX...this seems to be a LLJ convergence area where southwest winds are hitting south winds...edge of cap...and in the area along the warm front which extends from NE Texas into SW Arkansas.

That's a possibility, but the 18z NAM also shows widespread precip and cloud-cover over northeast Texas, which removes any surface-based instability. Check out the 18z NAM CAPE forecast valid at 21z: http://wxcaster2.com/CENTRAL_MESO-ETA212_SVR_CAPESRHSWEAT_51HR.gif ... :eek: (that EEK is for the total lack of instability north of I20/I30)

Destabilization occurs (in the forecast, at least) rapidly after 21z, with >1000 j/kg CAPE developing northward into northeastern Texas by 0z and thereafter. That's a possibility, but I'm always hesitant of model forecast of strong destabilization after 21z. Kind of reminds me of the 3-30-07 bustola.

Of course, it's important to remember that this is just one solution from a model that hasn't been terribly consistent the past couple of days, so I'm not too confident in such a dire solution yet.

[Jonathan Racy]

We have the ability to issue Day 3 moderate risks. It would consist of a 45% severe probability. We can also issue "hatched" areas for significant severe. The ability to issue Day 3 moderate risks was implemented last February and has never been done to this date. Issuing a Day 3 moderate risk would require a lot of certainty in a highly volatile situation.

http://www.spc.noaa.gov/misc/SPC_Prob_Conv_Otlk_Change_20060214.html


Jon


Well first off I just want to say that the SPC has issued a day three MODERATE risk before. It didnt really verify in the target area, it was June-12-05 I beleive. They had a moderate risk up for the eastern texas panhand and western oklahoma down into the texas south plains. However as we all know the south plains had a nice localized tornado outbreak that day, but anyways back on subject.
This system is really complicating things for me. I live in SC Oklahoma so Location isnt an issue here. But I really would like to see the moisture much deeper and the storm track further to the north and west. Even though I do think north texas and southern Oklahoma WILL see tornadoes I dont know how widespread or significant they will be, or how chaseable these storms will be. Cape values around 1200j/k and extremely powerfull wind feilds may not be a good combination, and yet if very well might given the extreme dynamics and lift with this system. But Honestly in an environment such as this one I have seen that not enough cape and to much in the way of wind shear causes the towers to be ripped apart. Also this system may generate to many storms all at once. However If Isolated storms form or even a cluster of storms can form and ride along the warm front and establish good inflow then We should be all set. This storm just represents to many quetions right now for me. I will make a choice on whether I will go or not sometime tomarrow.

[Adam Atkins]

Model trends continue to throw on the brakes and dig this trough further south....00UTC NAM shows the triple point between Wichita Falls and Gainsville, TX. Mid-level flow still screaming and low level jet is now becoming better juxtaposed with the instability axis near the warm front and dryline. I'm becoming a bit more optimistic about storm chase territory and the overall setup.

[Jim Tang]

There have been two MDT Day 3's. One prior to June 10, 2005 (that one was a complete bust) and one was prior to Jan 2, 2006.

Basically right now I'm worried about the juxtaposition of the low level jet axis and the instability. Another thing is just where the sfc low is? The models continue to trend stronger and stronger with a high to the north, and thus the sfc low continues to be progged weaker and further south. Keep in mind that the ground and the water temps in the GOM are still relatively cold, and the LLJ will bring a relatively warm air mass just above the cold sfc, so the closer to the Gulf the warm sector is, the greater the chances are that it will be a cloudy, dirty, drizzly warm sector.

Finally if the forcing's too strong, stratiform rain will overspread the warm sector, limiting instability and ruining the setup.

[Chris C Sanner]

I agree Jim. I'm really concerned about this turning into the setup we had earlier this month which was a moderate 15% hatched tornado setup. We ended up with a bunch of rain and a few "spinners" on the front of an embedded squall line. Right now, I'm thinking the system will still be a bit further W than the models are predicting (still). I'm not convinced it'll progress as far eastward as progged. Right now, I'm thinking being close to the low might be a good idea if we can get some clearing. But either way there are way too many details to sort out and I'm not entirely convinced we're going to see a decent severe weather event at all yet until the bigger questions are answered, and there's a lot of em...

[Jonathan Racy]

My apologies to Ray and Jim. I stand corrected. There were indeed MDT Day 3s issued June 8 and Dec 31 2005, valid for 3 days later of course. And, the probability has to be 45% hatched to be a MDT, now for Day3. Sorry for the confusion.

JPR


There have been two MDT Day 3's. One prior to June 10, 2005 (that one was a complete bust) and one was prior to Jan 2, 2006.

Basically right now I'm worried about the juxtaposition of the low level jet axis and the instability. Another thing is just where the sfc low is? The models continue to trend stronger and stronger with a high to the north, and thus the sfc low continues to be progged weaker and further south. Keep in mind that the ground and the water temps in the GOM are still relatively cold, and the LLJ will bring a relatively warm air mass just above the cold sfc, so the closer to the Gulf the warm sector is, the greater the chances are that it will be a cloudy, dirty, drizzly warm sector.

Finally if the forcing's too strong, stratiform rain will overspread the warm sector, limiting instability and ruining the setup.

[SteveCarter]

Looks like things are starting to come together rather nicely now. This could possibly be a major outbreak..POSSIBLY..in and around the Arklatex. DP's will GREAT, moisture..no problem, and lapse rates, instability, etc etc etc...looking pretty impressive. Thinking about leaving Friday 5AM for Shreveport, LA...10 hour drive, then staying on the MS/AL line late Friday, to be ready for Saturday! lol Then "home" for Sunday.

[Ray Walker]

Ya I knew there was at least one Moderate day three. I couldnt remember the exact date tho. This system, (in my opinion) is going to suprise alot of use at the last moment. I think it will look good and like it will produce an outbreak and then bust or look like a bust and then produce an outbreak. However I think the front will end up further north than proged. But that is just a hunch, a gut feeling, but all the models keep shoving it further south. We shall see.

[Jonathan Racy]

I'll still have to side with the ECMWF and GFS for Friday. I
don't trust the NAM, unless the event is within 12-18 hrs.
With that in mind, I'm thinking two primary areas of interest
for Friday afternoon.

Huge upper low over the Grtlks region now will be slow to
give up the ghost, so I'm not certain that the warm front
will be any farther north than the Red River during this
entire event. The LLJ axis appears to translate well ahead
of the dryline, impinging upon the e-w oriented front over
northeast TX during the afternoon. Thus, I reckon that "streamer"
type showers (HCRs)/storms will gradually intensify during the
late morning/afternoon into supercells. As they approach the warm
front, they could produce tornadoes. This area may end up being
the primary show. SPC SREF sigtor numbers are quite high
bounded by a TX I-20/30 corridor mid-late aftn Sat. That classic
"kissing jet/butterfly" orientation to the H25 flow looks great
for a good number of storms, probably backbuilding into ecntrl
TX during the evening. This would be a challenging chase for
sure!

Farther w, dryline/front will likely ignite later as the
primary height falls aloft spread ewd. Suspect that the
region along the Red River where the moisture "bends-back"
toward the sfc low may be an interesting spot, particularily
in light of colder temps aloft. Otherwise, backing low-midlevel
flow regime may spell rather quick transitions into a mixed mode
mess. But, it will be interesting given the Nascar festivities in
Fort Worth Fri-Sat!

Jon

[Billy Griffin]

While I have no meteorlogical explanation at all to this, I'm starting to have second thoughts on whether the more southern track will actually verify. Also, I wonder if this system just might slow down, if ever so slightly?

No, not wishful thinking, as I am medically unable to chase. But I'll be cheering you guys/gals on! So let's just call it a "gut feeling," - - I'm just wondering if the storm track and associated triple point will set up somewhere over SW / SC or even up into central Oklahoma with the associated WF making it as far north as I-40? I know that would likely spell trouble for chase terrain, (as cells would track into the jungle of SE OK as they continued east) but perhaps some initiation could occur along the I-44 / Highway 81 / I-35 corridor in southern Oklahoma? Again, not consistent with everyone's forecast, but just my .02 worth. Just for kicks though, I'll be eyeing southern Oklahoma!

[Brian Stertz]

12z ETA shows that there is definitely one hard target between Palestine and Texarkana (possibly as far north as the Paris-Clarksville TX areas on the Red River as well) tomorrow for the good combo of shear and decent moisture SB & 0-3km CAPE is maximized in this area. This looks to me to be the most threatened area for tornadic supercells tomorrow. Hate to discount the dryline further northwest and west (which should have some very strong ascent by evening)..but as far as reasonably clear targets, this would be the zone. This Day 2 MDT risk seems very well supported. Just not the most chaser friendly part of Texas where things may get wild and wooly.

[matt patterson]

I wont rehash what has already been said but the area from Gainsville to Paris is really intriuging.... I do worry about how much destabilization will actually occur in the warm sector...This may keep me a little closer to the Western half of the TA.... I read the AFD from Fort Worth and i think they sum it up very well

FACTORS
LEADING TO THIS EVENT ARE: A 50+ KNOT MOIST LLJ (http://www.srh.noaa.gov/fwd/glossary/def/llj.htm)...VERY STRONG
DIVERGENCE (http://www.srh.noaa.gov/fwd/glossary/def/divergence.htm) AHEAD OF THE UPPER LOW...100+ KNOT 300MB JET (http://www.srh.noaa.gov/fwd/glossary/def/jetstream.htm)...7 TO 8
DEGREE MID-LEVEL LAPSE RATES...35-50 KNOTS 0-3KM SHEAR (http://www.srh.noaa.gov/fwd/glossary/def/shear.htm) AND 200+
HELICITY. EXPECT THE WORST FRIDAY AFTERNOON AND EVENING...
ESPECIALLY OVER THE EASTERN COUNTIES.


Cant wait to see what SPC says at 1730

[Jim Bishop]

It would appear there are two distinct regions to chase for this setup. The first is along the dryline near the Waco area east/northeastward late in the afternoon (easier target for me, personally). The second is right along the warm front much earlier in the afternoon along the I-20 corridor east of Dallas, maybe in the vicinity of Paris/Northeastern Texas.

I choose dryline convection because it should be both a more chaseable terrain and the storms should be more discrete & visible. The 12z WRF does break out convection in the Vicinity of Waco, or between I35 & I45 between 18z & 00z well south of the warm front along the dryline. The speed shear alone supports supercells, especially given the north-south orientation of the dryline. But the veered 850mb winds mediately east of the dryline concerns me a little. The storm motion will be northeast around 45 knots or more initially. So stormy should quickly move into a much better shear environment, and become tornadic supercells within a couple hours of initiation.

The other area is completely warm air advection storms - messy. The 0-1km helicity values will be incredible, so any discrete, surface based storms will probably produce tornadoes. These storms will be moving northerly rapidly socked in with low clouds. Given the less than ideal chase terrain, I really don't see a point in going up there for a chase. But, I would expect the highest probabilty of a tornado occuring in this target region.

[Glen Romine]

Huge upper low over the Grtlks region now will be slow to
give up the ghost, so I'm not certain that the warm front
will be any farther north than the Red River during this
entire event. The LLJ axis appears to translate well ahead
of the dryline, impinging upon the e-w oriented front over
northeast TX during the afternoon. Thus, I reckon that "streamer"
type showers (HCRs)/storms will gradually intensify during the
late morning/afternoon into supercells. As they approach the warm
front, they could produce tornadoes. This area may end up being
the primary show. SPC SREF sigtor numbers are quite high
bounded by a TX I-20/30 corridor mid-late aftn Sat. That classic
"kissing jet/butterfly" orientation to the H25 flow looks great
for a good number of storms, probably backbuilding into ecntrl
TX during the evening. This would be a challenging chase for
sure!



First off - thrilled to see SPC staff joining in on ST forecast discussions, I hope that you'll find time to offer insight on future events as well. As for tomorrow - there are several aspects that seem suspect to a big event coming together. That said, the lack of consensus in the primary forecast models - particularly with regard to surface evolution, plague a reliable forecast approach. The agreement among model is largely in place for a weak surface ridge setting up along the coast line, with a trend toward veering surface winds with time across much of the 'warm sector' (south of the warm front setting up from the Red River eastward) during the day. This seems to aid in persistent thick cloud deck forecast across much of east TX and LA during the day which could really slow the northward progression of surface moisture there as it will need to mix downward. Latest SREF trending toward focusing the instability axis to a narrower region along the western side, across east Texas during the late afternoon, with only a sliver of high confidence steep mid-level lapse rates by Friday evening. Surface winds are generally weak, and tending to veer during the afternoon particularly according to the GFS. Despite this, low-level shear is impressive with strong 850 mb flow, yet the flow is nearly unidirectional and shows little speed shear from that height up through mid-levels. I struggled to find forecast soundings near the warm front that showed any low-level instability despite very low LCLs. A sweet spot will probably come together somewhere in east Texas during the afternoon, but pinpointing where is appearing impossible at this stage.

It seems that the 00Z NOGAPS model run might be the exception (between 09Z SREF,12 Z NAM and 12Z GFS) for many of the noted low-level issues above - didn't look at the ECMWF. Other diffs between GFS and NAM is the latter has the lead shortwave extending much further south - potentially triggering convection early in the day across the warm sector which could markedly alter the evolution of the day. GFS tracks this feature north of the WF.

[Jeff Snyder]

My primary concern continues to be destabilization... Shear profiles will, no doubt, be very strong. The NAM continues, however, to indicate negligible CAPE until after 21Z, owing to widespread cloud-cover and precipitation keeping temperatures down near 60-65F, with an effective warm front south of I20 in the early-mid afternoon. Now, it does indicate rapid destabilization after 21Z across northern Texas, but I'm not terribly confident in that. The NAM also continues to indicate a narrow tongue of CAPE developing right along the dryline. However, with 45-50kt storm motion for storms except mature supercells, I fear that narrow axis will be outrun rather quickly by any storms that do develop on the dryline.

Of course, as has been known, a lot will depend upon the extent of overnight convection. If convection sticks around N Tx, we may not see any appreciable destabilization that may preclude the development of significant, tornadic (implied surface-based) supercells N of I20. Of course, if this convection fails to materialize overnight through tomorrow morning, there is the potential for ~2000 j/kg CAPE south of the Red River. I think there is a chance to see a high risk event tomorrow, but I think we'll see to see significant destabilization take place first. If not, I have large fears that we'll see something similar to what we saw on 3-30 -- a "waste" of a setup in which there was very impressive deep-layer and low-level shear in the 'warm' sector.

[Glen Romine]

Looking at the 1730 outlook - I'm surprised by the analogue case date given of March 28, 2000. Looking back at the event, it sure doesn't look too much like the forecast for tomorrow. About the best matching aspects are the 500 mb flow pattern east of the Rockies (horrble pattern match upstream). Thermodynamic aspects look quite different for tomorrow.
I have to look more into how those matches are made.

[Chris C Sanner]

Truthfully, I am carefully eyeing a possible cold core scenario under the low in SW Oklahoma. Instabilities around 1000-1500 j/kg with easterly surface flow and some modest dewpoints. Not the most ideal tornadic environment but we know how these scenarios can reward with less than ideal conditions. Plus it is a lot better chase terrain among other things over Eastern Texas. I also think its pretty apparent that the activity there tommorow might be embedded in a bunch of junk which isn't fun. A lot can and will change but I am definitely split on which one to head for tommorow.

[Alex Lamers]

Well I attached a little graphic I made of my thoughts for the event. I have highlighted the best threat region for tornadoes ~85 miles either side of a line from Vernon TX (50 mi WNW of Wichita Falls) to Jonesboro LA (60 mi ESE of Shreveport).

I'm gonna have to agree with Jeff though on pretty much everything he said - this event has the potential to be quite severe, but it is conditionally dependent on how the low stratus deck evolves through the late morning and early afternoon across E TX and S OK.

It seems like the stratus will persist through the day north of the warm front and for much of the daytime hours in the LLJ vicinity where strong warm air advection just above the surface will help maintain the inversion. By early in the afternoon the LLJ should have shifted largely east of I-35. NAM/GFS cloud cover progs then support the clouds slowly mixing out to the west of I-35 from west to east with a mid-level dry air intrusion and probably to a SCT cu field of sorts from the GoM coast northward into EC TX. This seems reasonable to expect. The question du jour seems to be whether or not we will be able to poke some holes in the cloud cover as far north as the warm front which would then allow destabilization over most of E TX. I'm not entirely sure this will happen to the east of I-35 during the daylight hours.

In fact I would tend to agree with Jon that we'll see "streamer showers and storms". I see this beginning around 15-16z and lasting through the afternoon in the LLJ, initially around the surface warm front and to the north, but quickly backbuilding into the LLJ's moisture feed. They may not be initially a tornado threat but enough elevated instability and strong directional shear exists to support supercells and a marginal large hail threat. As the afternoon wears on, with differential thermal advection (CAA aloft, WAA in the boundary layer) and perhaps some sunlight poking through in E TX, I would imagine a slight increase in instability would be in order with effective inflow layers becoming closer to the surface. Thus, 18-19z through dusk I would imagine an increase in storm intensity in the LLJ envelope to the south of the surface warm front. These strengthening supercells would then interact with the low-level vorticity near the warm front and perhaps spin up tornadoes. I like the 1730z outlook's interest in right movers along the warm front. If there are any real significant tornadoes I would expect them to be from supercells like that.

There may be initiation later in the afternoon along the dryline but shear profiles appear more unidirectional. Still 60-70 knots of effective bulk shear and steeper lapse rates compared to further east would support intense supercells with perhaps very large hail and straight-line winds. An isolated tornado maybe over pre-existing boundaries or close to the surface low.

Big question will be the evolution of cloud cover and unfortunately we probably won't know that until tomorrow. It's either going to be real good or real disappointing. Best of luck to all chasing...I think I'm going to sit this one out and watch the radar for someone. If anyone else wants someone as a "nowcaster" feel free to give me a call.

AJL

[Ilya Neyman]

Latest models are significantly slowing the evolution of the surface features for tomorrow, in fact both this morning's 12z NAM and GFS are actually in relative agreement in keeping the surface low back...way back across the southern or even southwestern TX panhandle at 18z!! As a matter of fact there is now a general consenus in the primary surface low only moving to near the Childress, Wichita Falls vicinity with a dryline extending southward and an east-west warm front in the vicinity of the Red River at 00z, with the cold front diving south through the panhandle...all setting up a classic triple-point warm sector possibly as far west as Wichita Falls on south. This is considerably further west than the E/NE of DFW and Arklatex region. Concerning instability models indicate a good amount of heating taking place especially dryline/west during the late morning and afternoon hours. It would not be out of the realm of possibilities to have the 850 flow develop more of a southerly component ahead of the dryline in light of the latest developments. If that comes to fruition, and with the backed surface flow, storm motions may be just a tad slower owing to that as well, and may not only be more chaseable but hang out in the warm/moist airmass longer. Interestingly enough, this forecasted setup bears some scary resemblances to the Red River Tornado Outbreak of April 10, 1979. The NWS has a great page on that particular event and Plymouth State Weather Center has an archive of upper-air data going back to the 1950s for anyone interested. Ironically enough, Wichita Falls was hit very hard that evening. A big thing to keep in mind is the huge Nascar venue going on this weekend at the Texas Motor Speedway with Qualifying day set to occur on Friday. People in attendance or headed to that event definitely need to stay tuned to the latest weather situation. All in all a very impressive synoptic set up! Good luck and stay safe to all planning on chasing and all who live in that area.

[Bob Schafer]

Is it just me, or.....

Somebody else look at this:

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_ten_030m.gif

Is your reaction also "HUH???????"

[SteveCarter]

Going to sit this one out too. To far to drive from South Carolina, given so many uncertainties surrounding this system. Every forecast out seems to be a little different than the previous one, but I'm not as optimistic as I was before. March 28, 2000 had 8 tornadoes...not a HUGE outbreak, but I also don't see a lot of similarities like the SPC apparantly does. Looking at the latest models, I DO think there will be some tornadoes, but in a localized area, and maybe even towards eveing, so........staying home on this one. May head out Saturday though into sGeorgia and sAlabama towards the Fla penisula. Good luck to all that head out tomorrow!

[Jeff Snyder]

Is it just me, or.....

Somebody else look at this:

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_ten_030m.gif

Is your reaction also "HUH???????"

LOL Nope, wouldn't surprise me... The NCEP models (NAM and GFS) have had poor run-to-run consistency in terms of the location of the surface low. All that said, I don't think I've ever seen a model forecast a surface low to be >1000 miles south of a forecast not more than 24 hours prior.

Actually, I would be surprised if the primary sfc low was that far south, and the model consensus seems to be for a sfc low N or NW of Forth Worth by 0z. The 18z NAM shows the sfc low S of Vernon TX (west of SPS), by 0z. It also shows widespread and persistent precipitation across most of eastern and northeastern Texas throughout the day. For some reason, 3-30-07 keeps coming to mind as I keep seeing this solution (strong shear, but widespread convection prohibits destabilization -- BUST).

EDIT: After looking at everything, I'm starting to prefer the dryline area, from near LTS to SPS and southward. The last several model runs (GFS and NAM) have indicated persistent precip in northeastern TX throughout the afternoon. I don't want to go southeast of Dallas (S of I20), and I'm not sure how much areas N of I20 will destabilize. In addition, forecast hodographs indicate the dreaded S-shaped hodograph in the 0-4km layer. For example, some forecast hodographs show the majority of the SRH in the 0-1km layer, with almost no streamwise vorticity in the 1-4km layer (nearly all cross-wise vorticity). Farther west, the hodographs are forecast to be more straight-line, but I'll take that over an s-shaped hodograph... My experience tells me that S-shaped hodographs favor cyclonic and anticyclonic supercells, but with mesocyclones (and mesoanticyclones) that are relatively short-lived. Moisture isn't as good across western North TX and southwestern OK, but cold mid-level temperatures yield a sounding / thermal profile that looks very similar to many of the "cold-core" events of the past few years. So, with the 12-18z model data, I'm thinking about playing the low-topped supercell threat in the LTS to SPS areas now (as opposed to the warm front / LLJ threat area in eastern TX).

[matt patterson]

I find it interesting that all the models (00z RUC and 00z NAM) are pulling a lot more quality moisture into the C/NW part of TX tomorrow.. and shunting overall return in NE TX... anyone have thoughts on this...Maybe the system is slowing down????

[Reed Timmer]

WOW the 00z WRF looks very favorable for tornadoes in N TX tomorrow...it's very similar to last night's run, with LLJ further west near the dryline at 00z...continuous 40 kt southerly 850 mb flow coincident with the instability axis.

I definitely like the more circular 850 mb low with this run...the diagonally-oriented, peanut-shaped low of the 12z run was trash.

I also see no similarity with March 28, 2000, except maybe after 00z when the LLJ kicked in. The 00z analysis that day had very weak low-level flow, even at the core of the LLJ. I bet the 03z analysis was MUCH different.

Good luck all.

[Jim Bishop]

I'm still planning on playing the dryline for tomorrow. The WRF shows convection firing by 00z across Central/North Central Texas somewhere between Waco and Dallas near or a little to the west of I-35. The 850mb winds even look more backed directly in front of the dryline too, so I'm more optimistic about tornado potential.

[Trey Atterbury]

I'm still planning on playing the dryline for tomorrow. The WRF shows convection firing by 00z across Central/North Central Texas somewhere between Waco and Dallas near or a little to the west of I-35. The 850mb winds even look more backed directly in front of the dryline too, so I'm more optimistic about tornado potential.

Im also going to stay around the dryline. Starting around Gainesville. Good road options going all directions. Good luck to everyone going out tomorrow and stay safe!

[afischer]

Looking at the new NAM, I still have the same concerns that the GFS has been giving for days. It looks like a corridor of destabilization will occur ahead of the dryline in the wake of the morning/early afternoon stuff... but it still seems like the 850mb flow wants to veer atop the dryline. Thus the forecast is for dewpoints falling off vertically rather than a nice deep moist layer, which won't bode as well for strong boundary layer destabilization. I'm sure some nice supercells will pop on the dryline west and southwest of DFW tomorrow afternoon as the upper wave slams into the area. However, I'm finding it hard to ascertain just how good the low-level shear will be with these storms. The 1km SRH will probably be do-able but it still doesn't look strongly favorable to me, with hodographs on the small side. The better 1km agl flow and stronger low-level shear appears to be forecast farther east in the "grunge." Of course, this is taking the model at face value, so who knows. If the LLJ ends up being a little more brisk and less veered just ahead of the dryline (so that surface-based storms and strong low-level shear are definitively co-located), I'd be pretty excited for some tornadoes.

[Jason A.C. Brock]

I dont like all the convection out west and it seems to still be growing and building south. That could give us a crapvection chase tomorrow but if it can somehow clear off behind all the mess we could be in business. I am still thinking we may see the moderate risk pulled even jsut slightly West perhaps even as far as here in Wichita Falls which would make the area along U.S. 287 from Wichita Falls to Forth Worth certainly worth watching. Lots of good roads off 287 also except you get into some hills from Bowie to Fort Worth and to the South on into areas like Jack Young Palo Pinto Parker Counties. This is still better chase terrain however than SE OK. If things do turn out to verify for areas further East as advertised the area around Paris Texas actually isnt too bad for chasing at all. I do intend to stay out of the DFW metro if possible but now that I said that ill find myself there. I really hope this thing slows down and gives us some chasing NW and W of the DFW area tho.
Its looking less likely due to the convection out West but if I wake up in the morning to even partially clear skies and we have made to to 55-60 dews or more and the surface low is near Childress.....let the games begin. :-)
This will actually be a rather neat scenario to watch play out tomorrow for those armchair chasing at work etc. The upperlow back to the NW interacting with what moisture the surface low throws up its way will be interesting. NW Oklahoma will be a very raw place to be on Saturday with temps close to 50 and winds close to 40. Most of Texhoma will be for that matter.
I am also wondering if we may see an outflow boundary setup tomorrow as well....who knows where....or will this all just kinda be merged together along with the dryline and or warmfront.....I guess anyones guess is as good as anyones :-p

[Angie Norris]

The more I look and think about it, northwest TX looks like the place to be tomorrow. Moisture is an issue, as it looks like Tds will be in the upper 50s for the most part, and the lack of surface warming seriously worries me. I think any leftover cloud cover from convection tonight will further inhibit warming as well. I'll probably be playing the dryline/triple point area (thinking Wichita Falls for starters and adjust eastward as needed).
Good luck and safe hunting to all tomorrow!!!

[Alex Lamers]

Studying for a couple tests right now, but I had to chime in on the target picking in N TX for tomorrow. IMO playing the dryline will be a mistake. The last few SREF runs now are very consistent in developing a dry air conveyor belt around the south end of the cyclone in the wake of the LLJ. I would expect the dry air to mix down and help cap off the atmosphere. At the very least, clearing skies will allow for strong heating and the boundary layer flow should veer to a more southerly or even south-southwesterly direction. Hodographs quickly become more linear in this region. So even if storms manage to refire here, they probably wouldn't be a major tornado threat.

Meanwhile SREF and other models showing tight SBCAPE gradient along the surface warm front in the afternoon. I can't remember where, but I remember some training in the past few years that indicated mesolow formation along a boundary pretty normal to an LLJ is highly likely. The crux of these two features tomorrow will most definately be east of I-35. IMO there will be a mesolow developing in this area which will likely eventually become the primary surface low as upper level height falls spread past the dryline by evening. This should back and locally enhance the surface flow over far NE TX. Provided some clearing south of the sfc warm front in E TX which seems increasingly likely, I think there should be a real substantial tornado threat in this region. Look out from DFW to SHV.

More later maybe. I hate tests...grr...

AJL

[Tim Marshall]

TARGET: SEYMOUR-WICHITA FALLS, TX TIME OF DEPARTURE: 10 AM. A classic tornado setup is underway today. It is all coming together from great deep layer shear, to ample surface moisture, to a formidable dry punch, and perfect juxtaposition of narrow jets. It is hard to contain the excitement as it looks so good on paper. Yes, I was glad to see there wasn't a squall line to Del Rio this morning. The MCS over OK doesn't bother me as it will just enhance the warm front across the Red River. So what could go wrong today? For one thing, storms will be many and be fast moving. The Red River will pose a significant barrier to cross. My strategy is to stay in TX and pick off the storms as they come to me. I will play north of the dryline bulge and keep my options open about the warm front/triple point or heading south to I-20. The Dallas area will be under the gun later this evening and I don't want to miss that. There are thousands of RV's at Nascar. Large screens have been erected at the raceway. Folks will be crowding the stands tonight as a movie will be shown paying tribute to the late Dale Earnhardt -just about the time baseball hail could be falling. Be careful. TM

[Mikey Gribble]

I have just started to glance things over, so I don't have much of an opinion yet. I am 90% sure I won't be chasing today. I just don't think I could make it to my target in time considering that I can't leave ICT until around 10. There is that 10% chance I may pull the trigger at the last minute though. Anyways, if anybody wants any nowcasting help I will probably be keeping a close eye on things after 10AM, assuming I don't chase. Send me an email or a PM if I can help. michael_gribble@yahoo.com
Radar, WV imagery, and WRF precip. graphics all indicating that we have a good shot at getting some insolation over the warm sector. I am definitely more optimistic about that this morning. Mid to upper 60 dewpoints well on shore already. Last night's CRP sounding shows that moisture along the coast is plenty deep. RUC does have LLJ veering more than the NAM. I'm not a fan of the RUC though and I'm not buying it. Regardless, shear is definitely not going to be a problem. I would setup half way between Fairfield and Lufkin. I think you could pick up a storm fairly close to there later this afternoon and follow it NE as it moves intot the stronger low-level shear. Do that, and I think you're golden. Good luck to everybody who heads out today. I think you got a good shot at a couple tornadoes.

[Evan Stubbart]

I'm heading out now to get some work done in Graham, TX. My plan is to target a box around Wichita Falls down to Graham and ride the storms back towards the DFW area. I'm a bit worried about the cloud cover this morning, but we'll give it a shot. I can't pass up an opty like this so close to home. Good luck to all!

[Glenn Dixon]

Wow - targets from Shamrock to Shreveport. It might be a good thing that I can't leave work until noon here just north of the D/FW metromess. Targeting should be easier by then.......???

[update] - Don't get off work until noon, but tentatively targeting Wichita Falls

[Tony Laubach]

Tom Dulong, Jenn Brindley, and myself are sitting in the lobby of our hotel in Wichita Falls planning our escape. Part of me says to sit right here and wait like a good dog; the other part of me wants to get south towards I-20 a bit and ride the warm front, moving north with it til storms fire.

Cloud cover evident by looking outside, visible shows thinning clouds to our southwest near I-20. Think we'll head south out of here along Hwy 281 towards the Mineral Wells/Stephenville area. However, also liking the models interpretation of a dryline buldge north of I-20 today, which makes Wichita Falls an interesting scenario.

Moisture, shear, dynamics; it all looks to be well in place today, guess the hard part is which way to go with it all! One could likely plead a convincing case for a variety of targets today, so choosing one over the other is a matter of flipping a coin I think. Hate to think I'll reduce myself to that, but wouldn't be surprised if I brought a quarter out as a last choice. None-the-less, it'll be an active day today with plenty of potential, so everyone be safe and happy hunting!

[Doug Mitchell]

Currently sitting at a HoJo in Denton, TX after booking it from Lawrence at 1:30 this morning. Still not completely sure if I want to play WF here or dryline further west. A big problem I can see here is qualifying for the Nextel Cup Series event is happening at the Texas Motor Speedway today. The motel here is booked solid with race fans and that will make my road options tricky if I get caught in traffic. So a heads up to everyone chasing today...try to avoid the Fort Worth area if possible.

[Gabe Garfield]

What a difference a day makes.

My primary concern (cloud cover) has been addressed. I was expecting to wake up and see a huge mass of precipitation from Austin northward, but nothing of the sort has happened. In fact, I wouldn't be surprised if the warm front made much better progress northward (maybe as far as the Red River). Thus, I expect the best potential for tornadic activity may shift northward toward the Denton/Gainesville area. I certainly hope this is the case because I am quite concerned about the DFW metroplex today (not to mention it would be easier to chase).

Gabe

[Brian McKibben]

Target area if I were chasing would be along the dryline near the triple point. Current surf. obs show the low to still be out in West TX. Warm front extending from near Lub to Waco with Tds well into the 60s within the warm sector. There is pletiful sunshine along the dryline and the clouds are beginning to be mixed out just west of I-35 in TX. Winds backing near triple point will help provide strong low-level rotation for storms.

April 7th, 2002 Throckmorton tornado comes to mind.

[Karen Politte]

Cyber chasing today stuck at work - my long vacation weekends to chase don't start until May.

Wanted to chuck some first-hand terrain info. out there regardless...

Chasers should be aware that the area south from Texarkana to Shreveport on Hwy 71/549 is pretty chaseable in certain areas. It is partly flat river valley and has many scrub fields. The road network still sucks, though.

Also - if chasing here please be careful with the highway. They are in the process of building a NEW interstate/turnpike-type thing from Texarkana to Shreveport directly paralell to the old highway that is NOT on any of my maps. It is a good high-speed option and it comes out on I-30 in AR east of Texarkana - but it dead-ends down south before you enter LA and then you go back to the old 2-lane highway.

Good luck to any out chasing - I'll just sit and enjoy the show while it rains on me. ;)

KL

[Brian Stertz]

The 12z RUC sure has a nice theta ridge poking up towards the Graham -Jacksboro TX area by afternoon, with a hard target east of the triple point between Ft. Worth and Nocona TX. This could be a real wild event, especially if the warm front is more northbound and down than the models are catching on to. Right now the WF appears to be along a line from Aspermont to just south of the DFW Metroplex. The "super juice" is not too far away from being into the mix...and looks to be a lot farther along than I had ever expected. Good luck to those chasing. Recovery seems to be pretty much a lock at this point south of a Jacksboro to Greenville TX to Carthage TX line. It could put the DFW Metroplex under the gun by this afternoon.

[Donald Giuliano]

The dryline possibilities do not impress me at present, since the NAM/RUC have a lead 850mb trough axis that swings over the dryline around 18-21Z, junking out the low-level shear for a pretty large region ahead of the dryline. The CAPE is good there, but the LLS is poor by 00Z. Further into the warm sector, in east TX, where the shear looks much better, and the CAPE is sufficient, things look more interesting to me large-tornado wise. I am concerned about whether or not initiation will happen that far ahead of everything, but the models are firing convection there, which is a promising sign. Perhaps they are forecasting a small vort max similar to 3/28 of this year to help get things going there?

All that said, I would probably chase the dryline today if I were going, for the simple reason that the only alternative is chasing the piney woods. I'll trade the 10 times better roads/visibility west of I-35 for the better dynamics further east, especially since a lot of times the models push the low-level dynamics further east than verifies. It's entirely possible (not likely given the situation, but possible) that the good shear will be backed up to the dryline at 00Z, in which case watch out Dallas.

Complicated situation today, best of luck to those who go out.

[Chris Wilburn]

If I were chasing today I would target the triple point area. I would wait for something to fire a bit south on the dryline and wait on it as it moves north . Moisture recovery is almost certain at this time as Denton, Tx to Dallas and points just south and west of Dallas are already mid 50's. You could play just the warm front east of Dallas if you wanted and may have just as much luck, but I like the dryline/triple point play for terrain reasons. I would setup just west of Dallas and find a good place for data. Like always it will be key to keep an eye on the boundaries (dryline and warmfront) and make sure you know where they are. With CAPE near 2,000 J/kg, helicity values very high, and td's in the mid 60's this will be a very interesting day. Would be nice to get a nice supercell to fire along the dryline and move north and cross over the warm front. Like SPC mentioned any right mover has a very high chance of producing tornadoes. I will sit this one out as I have to work tonight. As a side note the RUC only forecasts 500mb winds in the 60-80kt range which may help on keeping storm speed down more than what has been projected in earlier runs. Something to keep in mind. Like others I agree that Dallas/Ft. Worth may very well be under the gun today. If anybody needs any assistance I will be home monitoring things if anybody needs any help or info feel free to send me a pm. E-mail is c_wilburn@yahoo.com Good luck to everybody chasing today!

[Jason A.C. Brock]

For now I think Ill still stck it out here in the falls. I have every weather gadget here with multiple wx station TVs on Time Warner 17 and the KSWO 24 channel on 366 and of course TWC :-P. I also made a very nice pot of coffee jsut now so maybe that is a good omen. Seriously tho I will stick around Wichita Falls with plans to head south or SE. I may head down 287 towards Fort Worth or I might get something much more local and more South. It is jsut a wait and see game Id say the first initial chaseable storms will fire in an area outlined from Vernon to Seymour to Throckmorton and points East towards Graham Jacksboro & Gainesville. This woudl leave areas such as Wichita Falls Archer City Henrietta Noccona Bowie& Even Decatur under the gun early.
So basically East of a line from Vernon to Seymour to Throckmorton to I-20 & areas between I-20 & The Red River to DFW Wwill see the first storms fire off. I would still like to see the Moderate risk shifted NW some.

[matt patterson]

ON the HWY now... Interesting to see the new 14z ruc... Helicity has been pulled back to the west and moisture is also farther N and W by 23z... headed to gainsville and will evauate from there...

[Tim Vasquez]

I haven't had a chance to look at much data right now, but it's noteworthy that the warm front is relatively far south... Lake Charles - Jarrell - Brady - Ballinger. Lots of low ceilings and fog just north of the front in the Waco - Temple area. I haven't seen enough data to pinpoint any target, but this sure keeps north Texas and northeast Texas under the gun today assuming this area isn't too capped. The entire zone from Windthorst to Fort Worth to Corsicana looks interesting.

Tim

[Ray Walker]

I am in gainsville right now looking at data. I am thinking about heading to Denton and then East on HWY 380 to Greenville. That way I can stay out of Dallas and catch any storms to my south or comming my way from the Dallas area.

[Paul Stofer]

I agree with Tim. Dewpoints are also really rebounding. 17z is showing 55 dewpoints in Denton already. Myself and a few others are going to head north on 35 to Denton, check data again then probably head West a little on 380 picking a spot between Graham and Denton. Good luck all.

[Richard Halter]

This is a setup for some large tornado action - i would probably park myself west of Dallas/Ft. Worth and be ready to shift east. It looks like a pretty simple forecast really - the dryline is going to be very active, and the area along the warm front.

Not very scientific (I am at work and don't have the ability to sneak in too much more than I am able to now, but looking at the current SPC parameters, there isn't much need to be too analytical - the potential for a major tornado/supercell event is very significant, IMO. I would not be surprised to see the event upgraded to a PDS later today.

[afischer]

Tornado watch 133 in effect. If I were chasing today, I would avoid areas of far northwest TX like the plague and stay south where the warm sector is wider. E thru SE of ABI still looks like a sweet spot. Tornadic potential will be better if storms can form out ahead of the primary sfc confluence line. The storms will be truckin'... good luck 'n stay safe.

[Jeff Piotrowski]

The area from DFW to Waco along I-35 around 21Z- 3Z time frame best chance for tornados. It thinks the warm front will stay south of the DFW area with a double point nw of Waco.

[David Wolfson]

I was virtually staying the night in Wichita Falls, planning to ride US82 southeastward through the afternoon, with many south options to meet storms initiating to the south of the front. Watching the vis sat closely, am virtually on the road approaching Ringgold following the convergence eastward.

I'm very impressed with the obvious deep moisture pulsing generally up I-45 from the south and the latest RUC's surface convergence and backed flow entering the DFW met area in the 21-00Z period. This could be a very nasty setup.

[bill mudd]

headed south into throckmorton right now gonna play the areas east of there
but avoiding DFW like the plague:cool:

if anyone is available for a nowcast send me PM

[Tim Vasquez]

Updated surface analysis. The Throckmorton-Graham-Windthorst area still looks pretty good, especially with the surface-based cell getting its act together near Haskell TX. Looks like a tendency toward linear modes out west, esp with the evaporative cooling in west Texas creating hellacious surface winds and adding to convergence along the front, compounded by anvils being lofted NE along the front (seeding the entire front).

The warm front is moving slowly north and will probably be retarded somewhat by the showers that have chilled the DFW region over the past hour. I think that will keep targets locked pretty well to the areas west of Fort Worth for midafternoon, with a few more storms possible along the warm front southeast of the Haskell storm (which will need to propagate east to stay within the narrow notch of rich moisture). I'm not sure whether we can get initiation from I-20 southward, within the best moisture, but that does bear watching.

Yeah, DFW will be interesting later on.

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