SPC Outlooks

[Billy Griffin]

Quick question... how can you have even a 2% tornado risk and yet NOT be included in the "slight risk" categorical outline area? Seems I'm noticing this a bit more often lately with SPC.

[Skip Talbot]

The 2% line is below Slight criteria. See:
http://www.spc.noaa.gov/misc/SPC_Prob_Conv_Otlk_Change_20060214.html

[Billy Griffin]

Thanks Skip. I guess it would help if I would read up on this from time to time. LOL

Is this something that has changed over recent years (the criteria, that is)?

[Skip Talbot]

Yes, they've redone the percentages with some of the biggest changes being the 10% tornado and the removal of a high risk hail percentage. I believe, although I could be wrong, that 2% was always in the see text category though.

[Tom Tackett]

Two Percent has been a non-categorical outlook criteria with tornadoes for quite some time---likely since the SPC began issuing probability forecasts. I never remember seeing or reading that hail could be a criteria for a High Risk being issued. As far as I know, High Risk outlooks have always been reserved for potential tornado outbreaks and/or widespread high wind events/derechos.