SWODY1
SPC AC 282203
DAY 1 CONVECTIVE OUTLOOK AMEND 2
NWS STORM PREDICTION CENTER NORMAN OK
0503 PM CDT MON SEP 28 2009
VALID 282155Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER CNTRL AND NRN NY AND FAR
WRN VT...
...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL AND ERN NC THROUGH
SERN VA...
AMENDED FOR MID ATLANTIC
...VA/NC PIEDMONT...
A FEW VIGOROUS STORMS HAVE FORMED ALONG THE COLD FRONT FROM S CNTRL
VA INTO WRN NC. STORMS ARE EMBEDDED WITHIN SUPERCELL WIND PROFILES
AND WILL REMAIN CAPABLE OF PRODUCING ISOLATED DAMAGING WIND AND
LARGE HAIL NEXT FEW HOURS. ACTIVITY SHOULD BEGIN TO WANE AFTER ABOUT
02Z AS THE BOUNDARY LAYER BEGINS TO STABILIZE.
AS SUCH...HAVE INTRODUCED MARGINAL WIND/HAIL PROBABILITIES. FOR MORE
INFORMATION SEE MD 2045.
...NY..NRN PA...VT...
STRONG FORCING WITH AN UPPER VORT LOBE EXTENDS FROM LAKE ONTARIO
INTO NRN PA AT 19Z WITH A LINE OF STORMS ALONG THE LEADING EDGE OF A
DRY SLOT. THESE STORMS WILL CONTINUE TO POSE A WIND THREAT AS THEY
TRAVEL ACROSS NY. A LEADING AREA OF WARM ADVECTION RAIN WILL KEEP
INSTABILITY AHEAD OF THIS LINE LOW...AND FURTHER WEAKENING SHOULD
OCCUR WITH LOSS OF DAYTIME HEATING. THUS...HAS TRENDED THE ERN EDGE
OF THE SLIGHT WWD. TO THE W...LAKE ENHANCED ACTIVITY BENEATH RAPIDLY
COOLING MID LEVELS MAY YIELD EPISODES OF MARGINALLY SEVERE HAIL
AND/OR WIND. REFERENCE MD 2043 FOR ADDITIONAL INFORMATION.
...S CNTRL INTO SERN TX...
A VERY MOIST AND UNSTABLE AIR MASS EXISTS ACROSS SERN TX THIS
AFTERNOON WITH DEWPOINTS INTO THE MID 70S F. A SURFACE COLD FRONT
WILL CONTINUE TO DRIFT SWD AND WILL PROVIDE A FOCUS FOR CONVECTION.
WEAK WIND FIELDS AND RELATIVELY DRY AIR ALOFT SUGGEST MAINLY PULSE
CONVECTION CAPABLE OF STRONG TO POSSIBLY SEVERE WIND GUSTS. FOR
ADDITIONAL INFORMATION REFERENCE MCD 2044.
...SERN AL INTO CNTRL GA...
A WLY FLOW REGIME EXISTS ACROSS THE DEEP SOUTH NEAR THE BASE OF AN
UPPER TROUGH. WATER VAPOR IMAGERY INDICATES SUBSTANTIAL DRY AIR AND
SUBSIDENCE IS OVERSPREADING THE REGION. AT THE SURFACE...A COLD
FRONT EXTENDED FROM THE PIEDMONT INTO CNTRL AL WITH A MOIST AND
UNSTABLE AIR MASS AHEAD OF IT. CONTINUED HEATING AS WELL AS LOW
LEVEL CONVERGENCE MAY BE ENOUGH TO TRIGGER A FEW THUNDERSTORMS ALONG
AND AHEAD OF THE FRONT...BUT THEY WOULD LIKELY NOT BE LONG LIVED AND
POSE ONLY A MARGINAL WIND THREAT.
..DIAL.. 09/28/2009
.PREV DISCUSSION... /ISSUED 1113 AM CDT MON SEP 28 2009/
...NEW YORK...
VERY STRONG VORT MAX NOW MOVING INTO SWRN ONTARIO CLEARLY DEPICTED
ON W/V IMAGERY ROTATES NEWD UP ST LAWRENCE RIVER VALLEY BY THIS
EVENING. THE FORCED LINE OF LOW TOPPED THUNDERSTORMS CURRENTLY FAR
WRN NY/WRN LO IS TIED TO THIS UPPER FEATURE AND THE ASSOCIATED
STRONG MID LEVEL COOLING AND ASCENT.
BRIEF CLEARING IN THE WAKE OF LARGER SCALE BAND OF PCPN/CLOUDINESS
CENTRAL NY/PA COUPLED WITH THE MID LEVEL COOLING...RESULTS IN SOME
INSTABLITY...I.E. MLCAPES FROM 100-200 J/KG...TO SUPPORT LOW TOPPED
THUNDERSTORMS.
COMBINATION OF FAST STORM MOTIONS AND 60KT OF DEEP LAYER
SHEAR...SUFFICIENT FOR AT LEAST ISOLATED WIND DAMAGE AS THE LOW
TOPPED LINE PASSES.
PRIMARY THREAT OF WIND DMG EXPECTED TO BE LO COASTAL COUNTIES AND
NRN NY...NEAREST TRACK OF VORT MAX.
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