SWODY1
SPC AC 301941
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0241 PM CDT THU SEP 30 2010
VALID 302000Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID ATLANTIC
STATES/EASTERN NC...
...MID-ATLANTIC STATES/EASTERN NC...
FEW CHANGES TO PRIOR FORECAST REASONING AS BELOW. REGIONAL WSR-88D
VWP DERIVED WIND DATA CONTINUE TO REFLECT CONSIDERABLY STRONG LOW
LEVEL WINDS /50+ KT IN LOWEST 1 KM/ WITH ASSOCIATED AMPLE SRH
COINCIDENT WITH A VERY MOIST AIRMASS /LOWER 70S F SURFACE DEWPOINTS/
FROM NJ/PA AND THE DELMARVA VICINITY...INTO COASTAL NC. THIS
SCENARIO WILL REMAIN CONDUCIVE FOR ROTATING SHOWERS/TSTMS AND THE
POSSIBILITY OF A FEW TORNADOES/ENHANCED CONVECTIVE GUSTS. THIS WILL
MAINLY BE THE CASE ACROSS CURRENT TORNADO WATCH 689...WITH AT LEAST
SOME INCREASE IN THREAT ALSO POSSIBLE ACROSS COASTAL NC THIS EVENING
IN TANDEM WITH AN APPROACHING SURFACE LOW.
..GUYER.. 09/30/2010
.PREV DISCUSSION... /ISSUED 1051 AM CDT THU SEP 30 2010/
...NC INTO PA/NJ/NY TODAY...
MORNING WATER VAPOR LOOPS SHOW A DEEP UPPER LOW OVER AL/GA...WHILE A
PROGRESSIVE UPPER TROUGH MOVES ACROSS THE GREAT LAKES REGION.
ALSO...A STRONG SHORTWAVE TROUGH HAS ROTATED AROUND THE SOUTHEAST
LOW AND IS LIFTING NORTHWARD INTO WV/PA. THE RESULT IS A WIDESPREAD
PLUME OF SHOWERS AND THUNDERSTORMS FROM EASTERN NC INTO MOST OF THE
NORTHEAST US. VERY STRONG SOUTHERLY LOW LEVEL WINDS EMBEDDED WITHIN
THIS AXIS OF PRECIPITATION ARE YIELDING A CORRIDOR OF INTENSE LOW
LEVEL VERTICAL SHEAR...WITH 3KM SRH VALUES OF 500-700 M2/S2 FROM
EASTERN NC INTO EASTERN PA. AMPLE LOW LEVEL MOISTURE HAS OFFSET THE
WEAK THERMODYNAMIC PROFILE IN THE MID LEVELS TO PROVIDE JUST ENOUGH
CAPE FOR A FEW THUNDERSTORMS. TRANSIENT SUPERCELL STRUCTURES HAVE
BEEN NOTED ALL MORNING...PARTICULARLY OVER SOUTHEAST VA AND
NORTHEAST NC.
PRESENT INDICATIONS ARE THAT A NARROW AXIS OF EMBEDDED SUPERCELLS
WILL PERSIST THROUGH THE AFTERNOON...ALTHOUGH MODELS INDICATE THAT
VERTICAL SHEAR WILL WEAKEN SOMEWHAT WITH TIME. THE MORE PERSISTENT
CELLS WILL REMAIN CAPABLE OF ISOLATED TORNADOES.
...EASTERN NC TONIGHT...
LATER TONIGHT...THE REMNANTS OF NICOLE WILL LIFT NORTHWARD INTO
EASTERN NC AND PROVIDE ANOTHER PERIOD OF STRONG VERTICAL SHEAR AND
LIFT. FORECAST SOUNDINGS AFTER DARK SHOW THE RE-DEVELOPMENT OF
INTENSE SRH VALUES /500+ M2/S2/...SUGGESTING THE RISK OF SUPERCELLS
CAPABLE OF A FEW TORNADOES OVER FAR EASTERN NC TONIGHT.
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