NWS STORM PREDICTION CENTER NORMAN OK
0852 PM CDT SAT MAR 31 2012
AREAS AFFECTED...CNTRL/ERN IA...NWRN IL
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 010152Z - 010245Z
AN INCREASE IN TSTM COVERAGE IS ANTICIPATED THROUGH THE LATE EVENING
HRS FROM CNTRL IA EWD INTO NWRN IL...WITH A PRIMARY THREAT FOR LARGE
HAIL. CONSIDERABLE UNCERTAINTY SURROUNDING SPECIFIC TIMING/MAGNITUDE
OF SVR POTENTIAL EXISTS...BUT CONVECTIVE TRENDS ARE BEING MONITORED
FOR A POSSIBLE WW...PERHAPS AS SOON AS THE NEXT 1-2 HRS.
SFC ANALYSIS FROM 01Z PLACES A WARM FRONT FROM 30 SSE OTM TO 10 NNW
SUX. TO THE NE OF THE WARM FRONT...RADAR ECHOES HAVE DEVELOPED
APPROXIMATELY 40 W OF CEDAR RAPIDS...WITH A NARROW WAA REGIME AIDED
BY A 30-40 KT SWLY LLJ /PER DMX VWP/. WITH TIME...A GRADUAL
INTENSIFICATION/EWD EXPANSION OF TSTMS IS EXPECTED. STEEP MIDLEVEL
LAPSE RATES /SAMPLED AT 7-8 C/KM PER DVN 00Z SOUNDING/ AND MUCAPE
VALUES EXCEEDING 1000 J/KG...ALONG WITH MODERATE W-NWLY MIDLEVEL
FLOW...WILL SUPPORT ELEVATED TSTMS /SOME SUPERCELLS/ CAPABLE OF
PRODUCING LARGE HAIL AS THE PRIMARY THREAT. A MAJORITY OF AVAILABLE
HIGH-RESOLUTION CONVECTION ALLOWING GUIDANCE /INCLUDING 23Z WRF-HRRR
AND 12Z WRF-NMM/ APPEARS TO BE TOO SLOW/FAR EAST WITH INITIAL
CONVECTIVE DEVELOPMENT...BUT GENERAL TREND IS FOR A GRADUAL EWD
EXPANSION OF TSTMS INTO ERN IA AND EVENTUALLY NRN IL AS LOW-LEVEL
WAA BECOMES FOCUSED FARTHER E. CONSIDERABLE UNCERTAINTY SURROUNDING
EVOLUTION OF CONVECTION AND TIMING OF ASSOCIATED LARGE HAIL THREAT
REMAINS...BUT THE AREA IS BEING MONITORED FOR A POSSIBLE WW.
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