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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 771

NWS STORM PREDICTION CENTER NORMAN OK

150 PM CDT FRI AUG 12 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EASTERN NORTH DAKOTA

       NORTHEAST SOUTH DAKOTA



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 150 PM UNTIL 800

PM CDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 65

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 EAST

NORTHEAST OF DEVILS LAKE NORTH DAKOTA TO 50 MILES WEST SOUTHWEST

OF WATERTOWN SOUTH DAKOTA.  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.



DISCUSSION...MULTICELLULAR DEEP CONVECTION WILL LIKELY CONTINUE TO

INCREASE IN BOTH COVERAGE AND INTENSITY AHEAD OF A COMPACT SHORT

WAVE TROUGH MOVG EAST ACROSS ND THIS AFTERNOON. MODERATE

DESTABILIZATION COINCIDENT WITH LIFT ASSOCIATED WITH THE SHORT WAVE

TROUGH WILL LEAD TO OCCASIONALLY STRONG UPDRAFTS AMIDST GENERALLY

WEAK/LIMITED EFFECTIVE SHEAR. RELATIVELY LOW FREEZING LEVELS AND

MAGNITUDE OF BACKGROUND ASCENT/FORCING MAY OFFSET THE LACK OF

GREATER SHEAR AND ALLOW FOR A FEW MORE ROBUST STORMS PRODUCING HAIL.

IN ADDITION...AMBIENT VORTICITY IN THE STORM UPDRAFT LAYER AND

GREATER LOW LEVEL CAPE COULD SUPPORT AN ISOLATED BRIEF/WEAK TORNADO

EVENT OR TWO.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 55

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400. MEAN STORM

MOTION VECTOR 29025.





...CARBIN

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