AREAS AFFECTED...EXTREME ERN IA THROUGH NRN IL
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 282159Z - 282330Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...STORMS DEVELOPING FROM ERN IA INTO NRN IL WILL POSE A
THREAT FOR ISOLATED DAMAGING WIND AND LARGE HAIL THIS EVENING. WW
ISSUANCE WILL ULTIMATELY DEPEND ON CONVECTIVE TRENDS...AND IF STORMS
CONTINUE TO INCREASE IN COVERAGE AND INTENSITY...A SEVERE TSTM WATCH
MAY BE NEEDED.
DISCUSSION...RECENT TRENDS HAVE BEEN FOR STORMS TO INCREASE IN
COVERAGE WITHIN ZONE OF FRONTAL CONVERGENCE FROM ERN IA...EXTREME
NWRN IL AND CNTRL WI. DOWNSTREAM THE WARM SECTOR IS MODERATELY
UNSTABLE OVER NRN IL WITH 2000-2500 J/KG MLCAPE AND 7.5 C/KM 700-500
MB LAPSE RATES. LOW LEVEL WINDS HAVE VEERED AHEAD OF THE FRONT WHICH
IS SERVING TO LIMIT CONVERGENCE TO SOME DEGREE. ALOFT A WEAK IMPULSE
WAS INDICATED ON THE RAPID REFRESH ANALYSIS LIFTING NEWD THROUGH IA.
NEVERTHELESS...BOUNDARY LAYER TEMPERATURES HAVE CLIMBED TO AROUND 90
CONTRIBUTING TO A RELATIVELY WEAK CAP...AND STORMS MAY CONTINUE
DEVELOPING AS THE FRONT ADVANCES INTO NRN IL. WHILE SHEAR IN THE
WARM SECTOR IS WEAK...STRONGER FLOW ALOFT HAS OVERTAKEN THE FRONTAL
ZONE RESULTING IN 35-40 KT UNIDIRECTIONAL EFFECTIVE DEEP LAYER
SHEAR. BOTH MULTICELL LINE SEGMENTS AND POSSIBLY SOME SUPERCELL
MODES MAY OCCUR.
..DIAL/HART.. 05/28/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...ILX...DVN...
LAT...LON 41509100 42408990 42278799 40858926 40519187 41509100
