WATCHES: Severe Thunderstorm Watch Number 121

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Poster: SIU Weather Processor <ldm@WEATHER.ADMIN.NIU.EDU>
Subject: WATCHES: Severe Thunderstorm Watch Number 121
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WWUS20 KWNS 102042
SEL1
SPC WW 102042
OKZ000-TXZ000-110300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 121
NWS STORM PREDICTION CENTER NORMAN OK
340 PM CDT TUE APR 10 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

SOUTHWEST OKLAHOMA
NORTHWEST TEXAS

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 340 PM UNTIL
1000 PM CDT.

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 50
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST OF
ALTUS OKLAHOMA TO 30 MILES NORTH NORTHEAST OF SHERMAN TEXAS. 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...ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS
AFTERNOON OVER SOUTHWEST OK AND NORTHWEST TX...AHEAD OF DEEP SURFACE
LOW AND ALONG SURFACE WARM FRONT. THESE STORMS ARE EXPECTED TO
TRACK EAST-SOUTHEASTWARD IN VICINITY OF THE RED RIVER THROUGH THE
EVENING. AREAL COVERAGE OF STORMS MAY BE RATHER LIMITED.
HOWEVER...MLCAPE VALUES AROUND 1000 J/KG...COOL TEMPERATURES
ALOFT...STEEP LAPSE RATES...AND SUFFICIENT SHEAR FOR SUPERCELL
STORMS WILL SUPPORT A RISK OF LARGE HAIL ACROSS THE REGION.

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 400. MEAN STORM
MOTION VECTOR 28035.

..HART

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