

686 

WWUS20 KWNS 251808

SEL9

SPC WW 251808

ILZ000-KYZ000-MOZ000-260100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 549

NWS STORM PREDICTION CENTER NORMAN OK

105 PM CDT SAT JUN 25 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN ILLINOIS

       FAR WESTERN KENTUCKY

       SOUTHEAST AND EAST-CENTRAL MISSOURI



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 105 PM UNTIL

800 PM 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH

NORTHWEST OF SCOTT AFB ILLINOIS TO 40 MILES EAST SOUTHEAST OF

POPLAR BLUFF MISSOURI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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.



DISCUSSION...SMALL BOWING COMPLEX W OF STL IS EXPECTED TO CONTINUE

EWD ALONG IMMEDIATE COOL SIDE OF LOW-LEVEL BAROCLINIC ZONE WITH

ADDITIONAL STORMS LIKELY THIS AFTERNOON FARTHER S NEAR SYNOPTIC

FRONT AND RESIDUAL OUTFLOW BOUNDARY.  AIR MASS IS QUITE MOIST WITH

DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  WHEN COUPLED WITH DAYTIME

HEATING AND STEEP MIDLEVEL LAPSE RATES...MLCAPE VALUES RANGE FROM

1000-1500 J/KG ACROSS E-CNTRL MO TO 2000-3000 J/KG NEAR THE

CONFLUENCE OF THE MS/OH RIVERS.  GIVEN THE WEAKENING CAP AND

CONVERGENCE ALONG LOW-LEVEL BOUNDARIES...EXPECT STORMS TO INCREASE

IN COVERAGE AND INTENSITY THIS AFTERNOON.  THE PRESENCE 40-45 KT OF

DEEP WNWLY SHEAR WILL SUPPORT ORGANIZED STORM MODES INCLUDING

SUPERCELLS AND BOWS WITH THE PRIMARY HAZARDS BEING LARGE HAIL AND

DAMAGING WINDS.



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 27035.





...MEAD

