

585 

WWUS20 KWNS 121506

SEL0

SPC WW 121506

OHZ000-PAZ000-WVZ000-LEZ000-122300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 290

NWS STORM PREDICTION CENTER NORMAN OK

1005 AM CDT THU MAY 12 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND EASTERN OHIO

       WESTERN PENNSYLVANIA

       NORTHERN WEST VIRGINIA

       LAKE ERIE



EFFECTIVE THIS THURSDAY MORNING AND EVENING FROM 1005 AM UNTIL

600 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES WEST

NORTHWEST OF CLEVELAND OHIO TO 35 MILES SOUTHWEST OF ELKINS WEST

VIRGINIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 288...WW 289...



DISCUSSION...STORMS DEVELOPING WITHIN WEAK WARM ADVECTION REGIME ARE

EXPECTED TO INTENSIFY AS THE BOUNDARY LAYER WARMS. TEMPERATURES

RISING INTO THE UPPER 70S WILL EVENTUALLY PROMOTE SURFACE BASED

STORMS. EFFECTIVE SHEAR FROM 30-35 KT SHOULD SUPPORT MULTICELL AND

MARGINAL SUPERCELL STRUCTURES WITH LARGE HAIL AND DAMAGING WIND THE

MAIN THREATS.



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 31035.





...DIAL

