

420 

WWUS20 KWNS 111827

SEL1

SPC WW 111827

IAZ000-ILZ000-WIZ000-120000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 281

NWS STORM PREDICTION CENTER NORMAN OK

125 PM CDT WED MAY 11 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN IOWA

       NORTHERN ILLINOIS

       SOUTHERN WISCONSIN



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 125 PM UNTIL

700 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 95

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES NORTHWEST OF

OSHKOSH WISCONSIN TO 30 MILES SOUTH OF BURLINGTON IOWA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU1).



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 278...WW 279...WW 280...



DISCUSSION...TSTMS EXPECTED TO INCREASE IN COVERAGE AND INTENSITY

ACROSS THE WATCH AREA THROUGH THE AFTERNOON AS WEAK MID-LEVEL

IMPULSE TRANSITIONS ACROSS THE REGION AND ENHANCES LIFT ALONG

OUTFLOW/LAKE-BREEZE REINFORCED WARM FRONT SITUATED NW-SE FROM SRN WI

INTO NRN IL. VERY UNSTABLE AIR MASS SHOULD FUEL ROBUST UPDRAFTS

WHILE SHEAR ASSOCIATED WITH THE UPPER IMPULSE AND LOW LEVEL BOUNDARY

ACTS TO AID STORM LONGEVITY AND ORGANIZATION. ALONG WITH LARGE

HAIL...AN EVOLVING DAMAGING WIND THREAT MAY DEVELOP GIVEN MAGNITUDE

OF INSTABILITY AND ONGOING STRONG SURFACE HEATING AHEAD OF THE

CONVECTION. ISOLATED TORNADO POTENTIAL MAY ALSO EXIST NEAR THE

BOUNDARY WHERE BACKED LOW LEVEL WINDS WILL CONTRIBUTE TO LOCALLY

ENLARGED HODOGRAPHS AND STRONGER LOW LEVEL SHEAR.



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 26020.





...CARBIN

