04/28/05 FCST: OK, KS, MO, AR

[Mike Johnston]

Well, since SPC now has slight risk outlook for E OK, SE KS, SW MO, and NW AR for Thursday as a forcing mechanism may come through Thursday evening, suppose we better at least consider. Aside from the hedges mentioned in the outlook itself, I don't particularly like the positive tilt of the surface trough and the veering surface winds. However, CAPE and helicity appear at least workable, and given the climatological probabilities, decent upper air support, frontal boundary in the vicinity and approaching surface low - well, I guess Thursday shouldn't be completely ignored, if only for the implications overnight convection may have for Friday's eagerly awaited set-up.

 

[nickgrillo]

Don't see much in the way for anything 'chaseable' in the forecast for Thursday, except for the fact because of the instability/unidirectional shear, a few of the storms could have some damaging winds/large hail...

 

[Mike Johnston]

As SPC maintains slight risk over E OK, NW AR, and S MO this evening and overnight, monitoring of surface conditions today is indicated. Satellite shows very nice clearing moving into the area this afternoon. Dewpoint at Ft. Smith reached 55 at noon w/ east winds. SR Helicity is forecast around 300 m2s2 over the area at 00z. Eastward progression and N/S orientation of surface low later today and into this evening may determine whether convective initiation will occur during period of maximum instability. There does appear to be a slot of opportunity for backing surface winds along an axis from Ft. Smith to Springfield vicinity. Those getting an early start by heading east for tomorrow's chase may have at least some possibilities for intermediate event this evening.

 

[Mike Johnston]

As Svr Thunderstorm Watch now issued for the target area, note effective bulk shear now increased to 60 to 70 kt, w/ steepening lapse rates, and good crossover of 500mb and 850mb winds in the warm sector of the watch area. Nice heating, and actual dewpoints have nudged slightly higher than forecast for today. Tornado threat is officially listed as minimal at this point, but shouldn't be ruled out as 0-3km EHI of 2 now beginning to emerge.

 

[Mike Johnston]

OK, if something is to fire in this area this evening, should initiate in E central OK where convective inhibition is lowest and LFC heights are falling below 2,000m.