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000 

WWUS20 KWNS 202058

SEL7

SPC WW 202058

COZ000-NEZ000-SDZ000-WYZ000-210300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 587

NWS STORM PREDICTION CENTER NORMAN OK

250 PM MDT FRI JUN 20 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTH CENTRAL AND NORTHEAST COLORADO

       WESTERN NEBRASKA

       SOUTHWEST SOUTH DAKOTA

       EASTERN WYOMING



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 250 PM UNTIL 900

PM MDT.



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 80

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH

NORTHEAST OF GILLETTE WYOMING TO 40 MILES SOUTH SOUTHWEST OF

AKRON COLORADO.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



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 584...WW 585...WW 586...



DISCUSSION...ISOLATED THUNDERSTORMS HAVE DEVELOPED OVER ERN WY AND

SWRN SD...AND COVERAGE OF STORMS IS EXPECTED TO INCREASE DURING THE

NEXT 2 HRS AS LARGE SCALE ASCENT IN ADVANCE OF THE SHORT WAVE TROUGH

MOVING TOWARD THE ROCKIES SPREADS INTO ERN WY AND CO.  SURFACE DEW

POINTS GENERALLY IN THE 40S COUPLED WITH STEEP LAPSE RATES ARE

RESULTING IN UNSTABLE CONDITIONS WITH MLCAPE AROUND 1000-1500 J/KG.

PROFILERS/VAD WINDS SHOW STRONG WNWLY FLOW IN THE MID LEVELS AND LOW

LEVEL WINDS THAT VEER WITH HEIGHT...RESULTING IN 30-40 KT DEEP LAYER

SHEAR ACROSS THE AREA.  THIS WILL PROMOTE SEVERE STORMS INCLUDING

SUPERCELLS WITH PRIMARY POTENTIAL FOR LARGE HAIL AND DAMAGING

WINDS...ALTHOUGH A BRIEF TORNADO IS ALSO POSSIBLE DURING THE EARLY

PHASE OF SUPERCELL STORMS.



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 31020.





...WEISS

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