SWODY1
SPC AC 231951
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT WED SEP 23 2009
VALID 232000Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...PA/NY TO NEW ENGLAND...
FEW CHANGES NEEDED TO PRIOR OUTLOOK...WITH CONTINUED POTENTIAL YET
THIS AFTERNOON/EARLY EVENING FOR A FEW QUASI-ORGANIZED STRONG/SEVERE
TSTMS CAPABLE OF WIND DAMAGE. MULTIPLE CLUSTERS/LINES OF
SHOWERS/TSTMS WILL CONTINUE TO DEVELOP ALONG/AHEAD OF ADVANCING COLD
FRONT...WITH LATEST OBJECTIVE ANALYSIS/18Z PITTSBURGH OBSERVED RAOB
REFLECTING UPWARDS OF 750-1100 J/KG OF MLCAPE WITHIN A PREFRONTAL
CORRIDOR ACROSS PORTIONS OF NY/PA INTO WESTERN NEW ENGLAND. POOR MID
LEVEL LAPSE RATES/OVERALL MODEST BUOYANCY IS STILL EXPECTED TO
PRECLUDE AN ORGANIZED SEVERE RISK.
..GUYER.. 09/23/2009
.PREV DISCUSSION... /ISSUED 1128 AM CDT WED SEP 23 2009/
...SYNOPSIS...
THE STAGNANT PATTERN WILL PERSIST OVER THE CONUS INTO
TOMORROW...WITH THE POLAR JET CONFINED TO NEAR AND N OF THE
U.S./CANADIAN BORDER...AND THE QUASI-STATIONARY CUTOFF LOW OVER THE
CENTRAL PLAINS. THE CENTRAL PLAINS LOW AND ASSOCIATED STRONGER FLOW
ARE LARGELY REMOVED FROM THE MOIST WARM SECTOR FARTHER E INTO THE MS
VALLEY AND NW GULF OF MEXICO...THUS ORGANIZED SEVERE STORMS ARE NOT
EXPECTED IN EITHER AREA TODAY INTO TONIGHT.
...N/NW PA NEWD INTO NRN NEW ENGLAND THIS AFTERNOON/EVENING...
SOME THREAT FOR AT LEAST ISOLATED DAMAGING WINDS WILL EXIST THIS
AFTERNOON/EVENING FROM WRN/CENTRAL NY STATE INTO NRN NEW ENGLAND.
HERE...A MID LEVEL SHORTWAVE TROUGH AND ASSOCIATED SURFACE COLD
FRONT WILL MOVE ESEWD FROM ONTARIO/QUEBEC INTO WRN/NRN NY AND NRN
NEW ENGLAND THIS EVENING THROUGH TONIGHT. A PRE-FRONTAL CORRIDOR OF
MID-UPPER 60S BOUNDARY LAYER DEWPOINTS AND AFTERNOON SURFACE
TEMPERATURES IN THE 70S WILL DRIVE MLCAPE VALUES OF 500-1000 J/KG.
SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED ALONG AND IN ADVANCE
OF THE COLD FRONT THIS AFTERNOON FROM NW PA NEWD ACROSS WRN/NRN NY
INTO NRN NEW ENGLAND...WHERE WEAK LARGE SCALE ASCENT COINCIDES WITH
WEAKENING CONVECTIVE INHIBITION WITH DAYTIME HEATING/MIXING IN CLOUD
BREAKS. VERTICAL SHEAR IS FORECAST TO BE SUFFICIENT FOR ORGANIZED
SEVERE STORMS...INCLUDING SOME POTENTIAL FOR SUPERCELLS AND/OR
EMBEDDED BOWING SEGMENTS. HOWEVER...POOR MID LEVEL LAPSE RATES
/LESS THAN 6 C PER KM/ AND RATHER LIMITED INSTABILITY SUGGEST THAT
THE OVERALL SEVERE THREAT SHOULD REMAIN MARGINAL.
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