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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 313

NWS STORM PREDICTION CENTER NORMAN OK

1230 PM CDT FRI MAY 20 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND CENTRAL TEXAS



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 1230 PM UNTIL

800 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 75

STATUTE MILES EAST AND WEST OF A LINE FROM 10 MILES EAST

NORTHEAST OF SHERMAN TEXAS TO 15 MILES SOUTH OF SAN ANTONIO

TEXAS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 312...



DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND

INTENSITY THIS AFTERNOON ALONG COMPOSITE OUTFLOW/PACIFIC FRONT AS

REGION IS GLANCED BY VORTICITY MAXIMUM PIVOTING NNEWD FROM THE SRN

HIGH PLAINS.  AMBIENT WARM SECTOR AIR MASS IS CHARACTERIZED BY A

VERY MOIST BOUNDARY LAYER BENEATH A STEEP MIDLEVEL LAPSE RATE

PLUME...YIELDING MLCAPE VALUES OF 2000-3500+ J/KG.  REGION WILL

REMAIN ON SERN PERIPHERY OF STRONGER MID AND HIGH-LEVEL WIND FIELD

ATTENDANT TO ABOVE-MENTIONED VORTICITY MAXIMUM WITH SUFFICIENT

DEEP-LAYER SHEAR FOR ORGANIZED STORMS INCLUDING SUPERCELLS.  WHILE A

BRIEF TORNADO IS POSSIBLE...LARGE HAIL AND LOCALLY DAMAGING WIND

GUSTS WILL BE THE PRIMARY HAZARDS.



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 25025.





...MEAD

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