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WWUS20 KWNS 202003

SEL2

SPC WW 202003

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 172

NWS STORM PREDICTION CENTER NORMAN OK

405 PM EDT WED APR 20 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND EASTERN PENNSYLVANIA



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 405 PM UNTIL

1100 PM EDT.



HAIL TO 0.5 INCH 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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 50 MILES SOUTHEAST OF

ALTOONA PENNSYLVANIA TO 45 MILES NORTH OF WILKESBARRE

PENNSYLVANIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).



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 168...WW 169...WW

170...WW 171...



DISCUSSION...LOW-TOPPED TSTMS ARE GRADUALLY INTENSIFYING THIS

AFTERNOON ALONG COLD FRONT PUSHING EWD ACROSS THE REGION.  BREAKS IN

THE CLOUDS HAVE ALLOWED FOR A CORRIDOR OF STRONGER DIABATIC WARMING

WHICH IS SUPPORTING SBCAPE OF AROUND 500 J/KG.  GIVEN THE STRONG WLY

DEEP-LAYER WIND FIELD OBSERVED BY AREA VWPS...THE POTENTIAL WILL

EXIST FOR SMALL SUPERCELLS OR BOWING STRUCTURES WITH THE PRIMARY

HAZARD BEING DAMAGING WIND GUSTS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 350. MEAN STORM

MOTION VECTOR 27045.





...MEAD

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