4/17/04 FCST: MIDWEST/GREAT LAKES

[Robert Dewey]

Looks like the potential exists for some warm frontal activity across portions of the Midwest into the Great Lakes on Saturday...

Robert

[Tim Jones]

Robert,

Waiting for the OOZ ETA to come out, but a glance at earlier runs peaked my interest along the warm front somewhere in the vacinity of NE Nebraska, NW Iowa, SW Minnesota, SE South Dakota Areas. Moisture and CAPE values, along with 0-3KM helicites look to be quite adequate for supercells. Didn't look much at upper air but I did notice that the ETA was suggesting 16* temps at 850mb and 20* further south down the dryline. Also, am somewhat suspect of the timing up the energy as it seems to be lagging further to the West. We'll see what the new runs bring.

Tim

[Robert Dewey]

The 00Z ETA is looking pretty good...I expect two main areas of possible severe weather across the Midwest and Great Lakes...

The first area, chronologically, should be across WI/MI (central portions), as a wave rides along the warm front. Strong shear and relatively good instability (>1500J/KG), should produce a moderately sized MCS in that region, or possibly a larger scale bow echo, given decent winds aloft.

The second area, will be across IA during the evening (possibly southeastern IA/northwestern IL). Latest 00Z ETA shows high CAPE in excess of 2250J/KG and good low level helicities. Decent forcing along the warm front should provide a good focus, and model QPF agree that deep convection will probably occur (per this run anyway). Given the instability and shear, as well as the fact that forcing isn't too linear, supercells appear possible.

Robert

[Blake W. Naftel]

Finally just made some time to analyise the situation for SAT-SUN. Since this is a Saturday thread; will briefly comment on the situation. Not a fan of the ETA trends of mid-upper 60 Td's and feel the GFS is providing a more realistic approach. One can only put so much faith in models; alas, the roll of the dice has been made. I will be departing for the Hawkeye state Friday evening. Invision DSM as a good stopping/starting point; and will assess the situation Saturday morning.

It should be noted that a "BNIIB" advisory will be activated around 6pm CT for all of Iowa.

BNIIB = "Blake Naftel Induced Iowa Bust".

Good luck to all those grunge chasers whom venture out this weekend!

..Blake..

[Tim Jones]

The 00Z run of the ETA got me a bit more excited for the w/end - especially on Sunday (but that's another thread). I am a bit concerned, however, that surface based storms may not fire until late in the evening on Saturday - perhaps after dark.

Anyway, I wanted to pass along to you Blake and anyone else that might be targeting the DSM area, that there's a free WiFi internet company that's got some sites around the city. I hope I'm not getting off the subject here, but here's the link to any/all that might be interested:

http://www.i-spotaccess.com

Just set up a username and password and everything is free!

Good luck to all.

Tim

[Ben Cotton]

Well, I'm not in the mood for writing much of a discussion, but I will head out either this evening (Friday) or early Saturday morning, initially for KIOW. The dynamics look pretty good on this, the two main concerns are Eta overdoing the Tds and also the very high LCLs. I'm hoping that the LCL's will come down some, but that's a pretty shaky issue ATTM. As for Eta's Td initializations, I'm not so sure that's a big of a concern as some think it is. Yes, it has been too generous in the past, but last night, it was only 3-5 F off in Kansas City, and about 5-7 off over the GoM. It still is the biggest worry, though, and certainly bears monitoring.


Ben

P.S. BNIIB = \"Blake Naftel Induced Iowa Bust\". Sounds a lot like a term us Purdue folk use..... BICD, or Boilermaker Induced Convective Divergence.

[Mike Hollingshead]

http://www.wxcaster.com/modelskewt.php3?mo...STATIONID=72548 (http://www.wxcaster.com/modelskewt.php3?model=ETA&fcsthr=033&STATIONID=72548)

Then click on eta in upper left corner.....that is for Waterloo IA at 21z Sat.


As for the real world and the moisture. Umm.... http://www.rap.ucar.edu/weather/upper/oax.gif That should show you exactly how much those sfc TDs mean right now. That is for Omaha.

I'm hoping the Waterloo forecast sounding becomes reality. I'd say I believe in that deep moisture happening...ooh......5%...lol....but i'm 100% full of hope somehow it will. Looking around the plains right now says no way. But, that is not to say less then that can't be fun too!

[Dan Cook]

DP here's almost 60. I'll bet we will get there today.

Checked out some of the newest ETA runs for IL:

http://www.wxcaster2.com/CENTRAL_ETA_SFC_S...INDSLI_36HR.gif (http://www.wxcaster2.com/CENTRAL_ETA_SFC_SLPTMPDPTWINDSLI_36HR.gif)

http://www.wxcaster2.com/CENTRAL_ETA_SVR_C...HSWEAT_36HR.gif (http://www.wxcaster2.com/CENTRAL_ETA_SVR_CAPESRHSWEAT_36HR.gif)

[Amos Magliocco]

The ETA initializations for the western GOM have been off by anywhere from 8 to 12F over the last three runs. ETA continues this morning to overdo Gulf moisture. Several local discussions and SPC products have discussed the ETA problems with this event, and this morning's soundings make it clear that what we're seeing is a shallow layer of high dewpoints with very dry air above. So surface readings taken at 2 meters won't tell us much about the availablility of deep moisture necessary for surface based supercells and tornadoes.

The models can be wrong. Basing a forecast more heavily on the ETA than currnet observations, soundings, and sound forecasting principles is more perilous this weekend than usual, in my opinion. I hope I'm wrong since many friends of mine are chasing, and I'll be the first to congratulate them on a successful weekend.

[Jeff Snyder]

Good point... if you check out the OUN and DFW/FWD soundings from this morning, it shows very shallow moisture... In fact, the OUN sounding has moisture <900m thick. Most places in all-but-the-panhandle of OK NOW have tds >=60. With consistent fetch from the Gulf (Gulf trafectories aside), I really don't see how Tds won't be at least what they are now. HOWEVER, the big question will be whether the shallow moisture will be mixed out. If it is, then we'll have to say goodbye to the instability. If not, then we'll be game. Now, if only the Gulf hadn't been blasted by the system earlier this week... Can ya imagine how good this would be with true tropical air (deep, sfc tds 65-70 or higher), which would likely be the case if if weren't for that previous system?

[Michael Shively]

Well i just got the HWO from KDMX.....doesnt look to good:( initiation they say will be after dark.....and i dont chase after dark...i may head up there just to say i did, and because it is so close to me, but i wont be expecting anything....dont get me wrong, im not a pessimist, just a realist and i think sunday may be the "big" day.

[Shane Adams]

Originally posted by Jeff Snyder
Can ya imagine how good this would be with true tropical air (deep, sfc tds 65-70 or higher), which would likely be the case if if weren't for that previous system?

We all end up saying this alot in a given chase year....probably why you don't see many years like 2003. I'm amused this year by all the newbies who got spoiled last year....they be learnin' some harsh reality lessons of chasing in 2004.....namely, you don't usually get your way 9 out of 10 days :wink:

[Blake W. Naftel]

Currently about to depart Kalamazoo en route to pick up my chase partner Keith Brown in Chicagoland. Keith, Chris Snider (a MET. student from Central Michigan University - on his first chase ever), and myself will be heading to DSM tonight... and targeting NW IA (Storm Lake, IA) and points westward Saturday. Hopefully Chris will not experience the wrath of how Iowa feels about having me set foot on its manure enriched lands... but not expecting too much from Saturday. Sunday should be the better play IMO, but this is nature; alas, one can never tell.

As Jeff noted; concerned about the shallow moisture OUN and points across the plains are showing; even if St. Joseph, MO does have mid-60 Td's attm. I don't trust the ETA any further than I can throw it; and that machine at NCAR is pretty heavy. More in agreeance with the GFS; still concerned over the high LCL's; and like others... hope those levels will lower later towards dusk.

I've said it before, so I'll say it again... IOWA... DO YOUR WORST!!!!

..Blake..

[Jeff Snyder]

Originally posted by Shane Adams+--><div class='quotetop'>QUOTE(Shane Adams)</div><!--QuoteBegin-Jeff Snyder
Can ya imagine how good this would be with true tropical air (deep, sfc tds 65-70 or higher), which would likely be the case if if weren't for that previous system?

We all end up saying this alot in a given chase year....probably why you don't see many years like 2003. I'm amused this year by all the newbies who got spoiled last year....they be learnin' some harsh reality lessons of chasing in 2004.....namely, you don't usually get your way 9 out of 10 days :wink:[/b]

LOL, 9 out of 10? My luck seems to be more like 14 out of 15... LOL

I agree... especially considering this is April. Seems that we all end up saying this sort of thing in late winter or early spring setups... If only we had 65 tds, if only we had strong midlevel flow, if only we had a more backed winds, etc etc etc... Since we can't make the weather (not yet, at least), I'd rather wishcast away! LOL

Jeff

[Ryan Pfannkuch]

For what it's worth, the latest 15z RUC is now showing convective initiation from central-northern IA between 21-0z. This is a significant change from the 12z run that showed nothing going before dark.

Given the boundary now working northward into southern IA with a few 60 dewpoints along it, the stage could be set for another interesting evening in the area. If only deeper moisture were in place...

[ckbehnke]

I think the depth of moisture could be alot worse. Looking at 12Z sounding for DVN, it's not that bad. DVN is the more favorable sounding I believe due to it's relation to the frontal boundary. I am more worried about lack of favorable Jet structure up to 6Z, and no signs of a significant shortwave to help in synoptic scale ascent. I think it will be a matter of timing/hoping something discrete can go before the arrival of the LLJ

[Mike Peregrine]

Just posting the links to the 9hr RUC maps for this afternoon in IA for those who are interested while we're waiting for the 6hr update.

CAPE/CINH - http://www.rap.ucar.edu/weather/model/ruc0...hr_sfc_cape.gif (http://www.rap.ucar.edu/weather/model/ruc09hr_sfc_cape.gif) - indicates instability along the WF in the 2000 range, along with a gap in inhibition.

Convergence - http://www.rap.ucar.edu/weather/model/ruc0...hr_sfc_mcli.gif (http://www.rap.ucar.edu/weather/model/ruc09hr_sfc_mcli.gif) - looks inviting along the boundary - there is a plume that extends from TX up across the dryline in KS - but doesn't appear deep enough to be hopeful about sfc based convection as of this particular run.

Helicities in the 500-600 range (another concern for any still considering the DL, although the panhandle is decent.) http://www.rap.ucar.edu/weather/model/ruc0...hr_sfc_sreh.gif (http://www.rap.ucar.edu/weather/model/ruc09hr_sfc_sreh.gif)

Vertical motion/mixing panels - http://www.rap.ucar.edu/weather/model/ruc0...9hr_925_mxr.gif (http://www.rap.ucar.edu/weather/model/ruc09hr_925_mxr.gif) - again, depth looks good in vicinity of boundary.

Looks to me like Iowa holds the ticket at this point ... won't be making the drive today, though - got the car in shape and it's just all tricked out - can't wait to use it now. All the best for those heading out -

[Mike Peregrine]

By the way, Jon Davies has a really good explanation for cap estimation according to month:

http://members.cox.net/jondavies1/700mbTca...mbTcapguide.gif (http://members.cox.net/jondavies1/700mbTcap/700mbTcapguide.gif)

and explanation of 700mb temperature guidelines here:

http://members.cox.net/jondavies1/700mbTca...p/700mbTcap.htm (http://members.cox.net/jondavies1/700mbTcap/700mbTcap.htm)

Thought those are helpful for amateurs like myself -

[Michael Shively]

Just took a look at the radar from KDMX at 0006Z....looks to be some convection starting.....maybe....very weak returns, but are consistent with t-storm development....look for a watch to be issued shortly,as MD stated earlier....so far, no EXPLOSIVE development however

[Andrew Geil]

Got some little poofies going up around Kankakee, IL. Nothing to get excited about, but it's nice to look at from 40 miles away. Big... white... poofy clouds. Better then blue nothingness above.

[Michael Shively]

OK....NOW there is EXPLOSIVE development:) i think somebody needs to start a now thread on these storms in NC IA

[rdale]

Awaiting the NOW thread - here's the cell along the IA/MN line:

ftp://radioweather.us/dmx0055.gif