

941 

WWUS20 KWNS 202026

SEL6

SPC WW 202026

COZ000-NEZ000-WYZ000-210400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 606

NWS STORM PREDICTION CENTER NORMAN OK

325 PM CDT MON JUL 20 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF NORTHEAST COLORADO

       MUCH OF WESTERN NEBRASKA

       PARTS OF EASTERN WYOMING



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 325 PM UNTIL

1100 PM CDT.



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 80

STATUTE MILES EITHER SIDE OF A LINE FROM 50 MILES NORTH NORTHWEST

OF CASPER WYOMING TO 30 MILES SOUTHEAST OF NORTH PLATTE NEBRASKA.

 FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU6).



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...DEVELOPING UPSLOPE SPREADING SWD IN HIGH PLAINS WILL

ENHANCE SHEAR AND INSTABILITY FOR SEVERE THUNDERSTORMS IN A NWLY

FLOW REGIME.  STORMS ARE NOW DEVELOPING ALONG BOUNDARIES AND IN

UPSLOPE AREA OF BIG HORNS.  STORMS WILL CONTINUE TO INCREASE IN

NUMBER AND INTENSITY AS THEY DEVELOP SEWD THRU THE WATCH AREA.

PARAMETERS ARE IN PLACE FOR SUPERCELL FORMATION WHICH WILL ENHANCE

POTENTIAL FOR LARGE HAIL AND DAMAGING DOWNBURST WINDS.



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 32025.





...HALES

