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WWUS20 KWNS 201727

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 285

NWS STORM PREDICTION CENTER NORMAN OK

1225 PM CDT SUN MAY 20 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL UPPER MICHIGAN

       NORTHERN AND CENTRAL WISCONSIN

       LAKE MICHIGAN

       LAKE SUPERIOR



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 1225 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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 5 MILES NORTHEAST OF

HOUGHTON MICHIGAN TO 40 MILES WEST SOUTHWEST OF OSHKOSH

WISCONSIN.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).



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...STORMS ARE BEGINNING TO INCREASE IN COVERAGE AND

INTENSITY ALONG/AHEAD OF A COLD FRONT MOVING ACROSS WRN WI.  THE

ENVIRONMENT IN THE WARM SECTOR IS MODERATELY UNSTABLE WITH MLCAPE OF

1500-2000 J/KG AND CONTINUED AFTERNOON HEATING WILL FURTHER STEEPEN

LOW LEVEL LAPSE RATES. SWLY MID LEVEL WINDS OF 40-50 KT ARE

CONTRIBUTING TO FAVORABLE DEEP LAYER SHEAR SUPPORTIVE OF ORGANIZED

CONVECTIVE STRUCTURES INCLUDING A FEW SUPERCELLS AND/OR BOW ECHOES.

THIS WILL ENHANCE WIND GUST POTENTIAL WITH STRONGER STORMS...AND

STEEP MID LEVEL LAPSE RATES ABOVE THE PBL WILL ALSO PROMOTE LARGE

HAIL AS STORMS MOVE EWD/NEWD THIS AFTERNOON.



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 22030.





...WEISS

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