THE NWS STORM PREDICTION CENTER HAS ISSUED A * SEVERE THUNDERSTORM WATCH FOR PORTIONS OF NORTHWEST IOWA SOUTHWEST MINNESOTA NORTHEAST NEBRASKA SOUTHEAST SOUTH DAKOTA * EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 910 PM UNTIL 400 AM CDT. * PRIMARY THREATS INCLUDE... SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2.5 INCHES IN DIAMETER POSSIBLE SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 10 MILES NORTHWEST OF AINSWORTH NEBRASKA TO 60 MILES EAST NORTHEAST OF SIOUX FALLS SOUTH DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1). PRECAUTIONARY/PREPAREDNESS ACTIONS... 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...THIS SEVERE THUNDERSTORM WATCH REPLACES TORNADO WATCH NUMBER 336. WATCH NUMBER 336 WILL NOT BE IN EFFECT AFTER 910 PM CDT. CONTINUE...WW 337...WW 338...WW 339...WW 340... DISCUSSION...THUNDERSTORMS WERE INCREASING RAPIDLY ALONG SHARP QUASI-STATIONARY FRONTAL ZONE BISECTING NEB FROM SW TO NE. THIS DEVELOPMENT IS OCCURRING AMIDST A VERY UNSTABLE AIRMASS IN ONE OF THE FEW REGIONS ACROSS THE CENTRAL PLAINS THAT HAS NOT SEEN SIGNIFICANT CONVECTIVE OVERTURNING IN THE PAST 24H. DESPITE RELATIVELY WARM TEMPERATURES ALOFT...IT APPEARS THAT NEAR SFC-BASED PARCELS ARE ABLE TO OVERCOME INHIBITION AND SUPPORT CONTINUED STORM DEVELOPMENT. IN ADDITION TO INCREASING MASS FLUX ACROSS THE FRONTAL ZONE...LIFT OVER THE REGION MAY BE ENHANCED TONIGHT AS MCV/SHORT WAVE TROUGH EMERGES EAST FROM HIGH PLAINS CONVECTION. SHEAR/INSTABILITY WILL SUPPORT ORGANIZED/PERSISTENT UPDRAFTS CAPABLE OF BOTH LARGE HAIL AND HIGH WINDS. SOME POTENTIAL WILL EXIST FOR UPSCALE GROWTH AND MCS EVOLUTION THROUGH LATE TONIGHT/EARLY SATURDAY. AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR 26025. ...CARBIN
Posted on: Sat, 22 Jun 2013 02:12:56 +0000
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