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WWUS20 KWNS 190312

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 408

NWS STORM PREDICTION CENTER NORMAN OK

1010 PM CDT MON JUN 18 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST MINNESOTA

       NORTHEAST SOUTH DAKOTA



EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 1010 PM

UNTIL 400 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 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 70 MILES WEST

SOUTHWEST OF ABERDEEN SOUTH DAKOTA TO 45 MILES EAST NORTHEAST OF

REDWOOD FALLS MINNESOTA.  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 407...



DISCUSSION...POTENTIAL IS INCREASING FOR VIGOROUS TSTM DEVELOPMENT

ROOTED ABOVE THE BOUNDARY LAYER AS A FAST-MOVING LOW AMPLITUDE

IMPULSE SPREADS EAST FROM THE HIGH PLAINS...AND THE NOCTURNAL LOW

LEVEL JET STRENGTHENS TO AID DEEP-LAYER ASCENT ACROSS ERN SD AND WRN

MN THROUGH TONIGHT. PLUME OF STEEP MID LEVEL LAPSE RATES AND

ABUNDANT MOISTURE FLUX ON THE NOSE OF THE LOW LEVEL JET WILL FUEL

INTENSIFYING STORM UPDRAFTS AMIDST MORE THAN ADEQUATE EFFECTIVE

SHEAR FOR UPDRAFT PERSISTENCE AND ROTATION. SINCE STRONG

SURFACE-BASED INHIBITION WILL LIMIT BOUNDARY LAYER COUPLING...EXPECT

THE PRIMARY HAZARD FROM THIS DEVELOPING CONVECTION TO BE LARGE HAIL.

HOWEVER...WITH TIME...INTENSIFYING COLD POOL AND STRENGTH OF THE

MEAN-LAYER FLOW...MAY BE SUFFICIENT TO OVERCOME BOUNDARY LAYER

INHIBITION AND SUPPORT A FORWARD PROPAGATING MCS WITH AND INCREASING

CHANCE FOR DAMAGING WINDS. IF THIS SCENARIO OCCURS...GREATEST RISK

MAY EVOLVE AFTER MIDNIGHT ACROSS PARTS OF MN.



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 25030.





...CARBIN

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