

201 

WWUS20 KWNS 071702

SEL1

SPC WW 071702

COZ000-072300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 341

NWS STORM PREDICTION CENTER NORMAN OK

1100 AM MDT SUN JUN 7 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST COLORADO



EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 1100 AM UNTIL

500 PM MDT.



HAIL TO 2.5 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 55

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 20 MILES SOUTH OF

FORT COLLINS COLORADO TO 20 MILES EAST SOUTHEAST OF AKRON

COLORADO.  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...THUNDERSTORMS ARE BEGINNING TO DEVELOP ALONG THE FRONT

RANGE IN THE MOIST UPSLOPE FLOW REGIME TO THE N OF A SLOW-MOVING

FRONT.  SURFACE HEATING IN CLOUD BREAKS AND STEEP MID LEVEL LAPSE

RATES WILL CONTRIBUTE TO MODERATE INSTABILITY THROUGH THIS AFTERNOON

ON THE IMMEDIATE COOL SIDE OF THE BOUNDARY...AND STORM COVERAGE WILL

LIKELY INCREASE AS A MID LEVEL TROUGH MOVES NEWD FROM CENTRAL CO.

THE COMBINATION OF VERTICAL SHEAR AND STRONG DEEP LAYER VERTICAL

SHEAR WILL SUPPORT SUPERCELLS CAPABLE OF PRODUCING ISOLATED VERY

LARGE HAIL.  ISOLATED DAMAGING WINDS WILL ALSO BE POSSIBLE...AND AN

ISOLATED TORNADO CANNOT BE RULED OUT.



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 500. MEAN STORM

MOTION VECTOR 26025.





...THOMPSON

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