WATCHES: Severe Thunderstorm Watch Number 606

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

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