WATCHES: Severe Thunderstorm Watch Number 188

WWUS20 KWNS 260540
SEL8
SPC WW 260540
ILZ000-INZ000-KYZ000-261300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 188
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT THU APR 26 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

SOUTHERN ILLINOIS
SOUTHWEST INDIANA
WESTERN KENTUCKY

EFFECTIVE THIS THURSDAY MORNING FROM 1240 AM UNTIL 800 AM CDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTH
SOUTHWEST OF MOUNT VERNON ILLINOIS TO 65 MILES EAST OF OWENSBORO
KENTUCKY. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...CONTINUE...WW 187...

DISCUSSION...A SMALL CLUSTER OF STRONG-SEVERE TSTMS ONGOING OVER SRN
IL IS EXPECTED TO PROGRESS SEWD ACROSS WATCH AREA EARLY THIS
MORNING...FORCED BY DCVA ATTENDANT TO UPSTREAM SHORTWAVE
TROUGH...AND LOWER TO MID-TROPOSPHERIC WAA ASSOCIATED WITH A WNWLY
LLJ. AMBIENT INFLOW AIR MASS IS CHARACTERIZED BY A WARM BOUNDARY
LAYER AND STEEP LAPSE RATES...YIELDING MLCAPE OF 1500-3000 J/KG.
THIS INSTABILITY COINCIDES WITH 40-45 KT OF DEEP NWLY SHEAR WHICH
WILL SUPPORT THE POTENTIAL FOR EMBEDDED SUPERCELLS AND POSSIBLE
UPSCALE GROWTH INTO A BOWING MCS. DAMAGING WINDS AND HAIL WILL BE
THE PRIMARY SEVERE WEATHER HAZARDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 32030.


...MEAD

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