SWODY1
SPC AC 281627
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT MON JUN 28 2010
VALID 281630Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FROM THE
MID ATLANTIC TO SE NEW ENGLAND...
...MID ATLANTIC TO SE NEW ENGLAND THIS AFTERNOON/EVENING...
A DEEP CLOSED LOW OVER JAMES BAY WILL CONTINUE TO MOVE SLOWLY SSEWD
WHILE EMBEDDED SPEED MAXIMA ROTATE EWD AROUND THE SRN PERIPHERY OF
THE LOW. A PRIMARY EMBEDDED SHORTWAVE TROUGH OVER LOWER MI AS OF
LATE MORNING WILL EJECT EWD/ENEWD OVER THE SAINT LAWRENCE VALLEY
THROUGH EARLY TONIGHT. THIS TROUGH WILL BE PRECEDED BY A REMNANT
MCV THAT WILL MOVE EWD FROM ERN OH/WRN PA TO SE NEW ENGLAND THIS
AFTERNOON. AT THE SURFACE...THE SYNOPTIC COLD FRONT IS NOW CROSSING
INDIANA/NW OH/SW ONTARIO. A BAND OF RELATIVELY THICK CLOUD COVER IS
LIMITING SURFACE HEATING/DESTABILIZATION IMMEDIATELY E OF THE COLD
FRONT...AND THIS SHOULD CONTINUE TO BE THE CASE THROUGH THE
AFTERNOON ACROSS MUCH OF WRN/CENTRAL PA AND NY. FARTHER SE FROM THE
THICKER CLOUDS...STRONG SURFACE HEATING IS UNDERWAY ALONG THE I-95
CORRIDOR. ONCE SURFACE TEMPERATURES WARM INTO THE LOW-MID
90S...CONVECTIVE INHIBITION SHOULD BE LARGELY REMOVED AND
THUNDERSTORM DEVELOPMENT IS EXPECTED BY EARLY AFTERNOON NEAR THE
PRE-FRONTAL TROUGH AND GRADIENT IN CLOUD COVER.
THE WARM SURFACE TEMPERATURES AND AFTERNOON BOUNDARY LAYER DEWPOINTS
IN THE UPPER 60S TO LOWER 70S WILL SUPPORT MODERATE INSTABILITY
/MLCAPE NEAR 1500 J PER KG/...WITH SURFACE TEMP-DEWPOINT SPREADS
APPROACHING 20-25 F. THOUGH SOME GRADUAL WEAKENING OF THE 35-50 KT
WSWLY FLOW IN THE 850-600 MB LAYER IS EXPECTED BY MID AFTERNOON...A
CORRESPONDING INCREASE IN FLOW ALOFT WILL MAINTAIN SUFFICIENT
VERTICAL SHEAR FOR ORGANIZED STORM CLUSTERS...AS WELL AS THE
POTENTIAL FOR BOWS AND EVEN SUPERCELLS ACROSS SE NEW ENGLAND GIVEN
THE PRESENCE OF MODERATE INSTABILITY. THE COMBINATION OF
FACTORS...INCLUDING RELATIVELY WARM TEMPERATURES ALOFT AND MODEST
MIDLEVEL LAPSE RATES...APPEARS SUPPORTIVE OF PRIMARILY A DAMAGING
WIND THREAT THIS AFTERNOON INTO THIS EVENING.
...OH/WRN PA AND NY THIS AFTERNOON...
THE SYNOPTIC COLD FRONT WILL PROVIDE A FOCUS FOR THUNDERSTORM
DEVELOPMENT...AS NOTED BY DEEPENING CUMULUS AND SMALL CB/S ALONG THE
BOUNDARY IN NW OH AS OF 16Z. HOWEVER...POOR MIDLEVEL LAPSE RATES
AND CLOUDS WILL LIMIT THE POTENTIAL FOR DESTABILIZATION...AND IT
APPEARS THAT MAINTAINING ONLY LOW DAMAGING WIND PROBABILITIES IS
APPROPRIATE FOR THIS UPDATE. REFER TO MESOSCALE DISCUSSIONS 1151
AND 1152 FOR ADDITIONAL INFORMATION.
...SRN APPALACHIANS TO CENTRAL/E TX THIS AFTERNOON...
A COLD FRONT WILL SAG SEWD ACROSS KY/TN/AR/SE OK THROUGH THE
AFTERNOON. STRONG SURFACE HEATING S OF THE FRONT WILL AGAIN
CONTRIBUTE TO MODERATE AFTERNOON INSTABILITY IN AN ENVIRONMENT OF
WEAK VERTICAL SHEAR AND BOUNDARY LAYER DEWPOINTS IN THE 70S.
THUS...PROFILES WILL BE FAVORABLE FOR PULSE-TYPE STORMS WITH THE
POTENTIAL FOR ISOLATED STRONG DOWNBURST WINDS ALONG THE FRONT...AS
WELL AS WITH THE OUTFLOW-ASSISTED SEA BREEZE ACROSS THE GULF COAST
AND THE HIGHER TERRAIN OF THE SRN APPALACHIANS THIS AFTERNOON.
..THOMPSON/DEAN.. 06/28/2010
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