SEVERE THUNDERSTORM WATCH

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1230 PM UNTIL 800 PM EDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.


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...TSTMS EXPECTED TO CONTINUE INCREASING ALONG DIFFUSE COLD FRONT NOW BISECTING PA. OTHER STORMS MAY FORM AHEAD OF FRONT ALONG LEE TROUGH. STRENGTH OF DEEP UNIDIRECTIONAL WIND FIELD AND CONTINUED LOW LVL DESTABILIZATION LIKELY WILL LEAD TO INCREASED POTENTIAL FOR DMGG WIND GUSTS AS STORMS...INCLUDING A FEW SUPERCELLS...ORGANIZE INTO SHORT LINE/BANDS.



...CORFIDI

MESOSCALE DISCUSSION 1074

MESOSCALE DISCUSSION 1074
NWS STORM PREDICTION CENTER NORMAN OK
1035 AM CDT TUE JUN 22 2010

AREAS AFFECTED...WRN/CENTRAL PA...MD...PARTS OF ERN WV...NRN/ERN VA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 221535Z - 221600Z

WW IS BEING CONSIDERED FOR PARTS OF WRN/CENTRAL PA SWD THROUGH MD...PARTS OF ERN WV AND NRN/ERN VA.

SHORTWAVE TROUGH...CURRENTLY TRACKING EWD INTO THE LOWER GREAT LAKES/UPPER OH VALLEY PER WATER VAPOR IMAGERY...WILL MOVE EWD INTO NY/PA AND NRN VA/MD THIS AFTERNOON. 12Z UPPER AIR DATA INDICATED 40 KT WLY MIDLEVEL FLOW WITHIN THE BASE OF THIS TROUGH OVER OH. OBJECTIVE ANALYSES SHOWED EFFECTIVE BULK SHEAR ALREADY INCREASING ACROSS CENTRAL PA TO NRN VA AS THE STRONGER FLOW ALOFT SPREADS EWD. IN THE LOW LEVELS...SURFACE FRONT ATTENDANT TO THE SHORTWAVE TROUGH EXTENDED SSWWD FROM SWRN ONTARIO THROUGH CENTRAL OH. THIS BOUNDARY WILL CONTINUE EWD TODAY AND MARK THE WRN EXTENT OF THE SEVERE WEATHER THREAT.

CLOUDINESS/FILTERED SUNSHINE ACROSS PA...ASSOCIATED WITH CIRRUS AND LEADING BAND OF ONGOING CONVECTION OVER CENTRAL PA TO THE ERN WV PANHANDLE IS LIMITING SURFACE HEATING SOME THIS MORNING. THIS COMBINED WITH WEAK MIDLEVEL LAPSE RATES APPEARS TO BE RESULTING IN A SLOWER DESTABILIZATION OF THE AIR MASS THUS FAR. HOWEVER... FURTHER DIABATIC HEATING WITHIN A MOIST AIR MASS IS EXPECTED TO SUPPORT AT LEAST MODERATE INSTABILITY BY THIS AFTERNOON WITH MLCAPE 1000-1500 J/KG EXTENDING FROM OH INTO CENTRAL PA AND SWD TO VA/MD.

12Z WRF-HRRR SUGGESTED THE ONGOING STORMS OVER CENTRAL PA TO ERN WV PANHANDLE WILL CONTINUE TO WEAKEN...WITH NEW TSTMS DEVELOPING OVER WRN PA TO WV AROUND 17Z AS THE FRONT MOVES EWD. MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR UP TO 40 KT WILL SUPPORT ORGANIZED STORMS WITH A THREAT OF HAIL...STRONG WIND GUSTS AND A POTENTIAL TORNADO THREAT. THE TORNADO THREAT WILL BE GREATER IN ANY LOCATION WHERE LOW LEVEL WINDS ARE MORE SLY...HENCE INCREASING LOW LEVEL DIRECTIONAL SHEAR. GREATEST TORNADO THREAT SHOULD BE EAST OF THE MOUNTAINS. HOWEVER...FORECAST SOUNDINGS SUGGEST SURFACE WINDS
AHEAD OF THE FRONT IN WRN PA WILL REMAIN FAVORABLY BACKED TO SUPPORT A TORNADO THREAT WITH INITIAL ACTIVITY PRIOR TO WINDS VEERING WITH
FRONTAL PASSAGE.

..PETERS.. 06/22/2010

6/10/10: 4 Months Ago Today

6/7/10: Video - Incredible Lightning Strike

Video of a near-miss lightning strike in Norman, OK in July 2007.

6/6/10: Forecast - The Week Ahead

Showers and storms are likely today, with highs in the upper 80s as a cold front moves through the area.

Monday and Tuesday should be pleasant, with highs in the low 80s.

Shower and thunderstorm chances increase again Tuesday night and Wednesday with an associated cold front.

The front should clear the area on Wednesday night, allowing high pressure to move in with a return to sunshine and temperatures in the mid-80s on Thursday, Friday and Saturday.