SWODY1
SPC AC 151923
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0123 PM CST SAT NOV 15 2008
VALID 152000Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT FROM
THE LOWER HUDSON VALLEY SWD INTO ERN NC...
...SRN NEW ENGLAND TO THE ERN CAROLINAS...
DYNAMIC...LARGE-SCALE TROUGH CENTERED JUST E OF THE MS VALLEY WILL
ASSUME AN INCREASING NEGATIVE TILT OVERNIGHT AS STRONG
MID/UPPER-LEVEL JET STREAKS DEVELOP NWD FROM THE TROUGH BASE ALONG
THE ATLANTIC COAST. THIS EVOLUTION IS RESULTING IN CONSIDERABLE
HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT OVER THE APPALACHIANS...
WHICH WILL SPREAD EWD ACROSS THE REGION LATER THIS AFTERNOON AND
TONIGHT. IN THE LOW LEVELS...DEEPENING SURFACE CYCLONE CENTERED
OVER CNTRL PA AS OF 18Z WILL CONTINUE TO UNDERGO INTENSIFICATION
WHILE DEVELOPING NNEWD THROUGH CNTRL NY AND EVENTUALLY INTO ERN
QUEBEC. MEANWHILE...TRAILING...STRONG COLD FRONT /NOW EMERGING FROM
THE APPALACHIANS/ WILL SWEEP EWD THROUGH THE MID ATLANTIC COASTAL
STATES AND CAROLINAS BY LATER TONIGHT.
SSWLY 50-55 KT LLJ IS SUPPORTING THE NWD FLUX OF A MOIST BOUNDARY
LAYER THROUGH THE MID ATLANTIC STATES INTO SRN NEW ENGLAND WITH
DEWPOINTS INCREASING THROUGH THE 60S. AT THE SAME TIME...BREAKS IN
THE CLOUDS OVER THE CAROLINAS INTO THE DELMARVA AND DE RIVER VALLEY
HAVE ALLOWED TEMPERATURES TO INCREASE INTO THE 70S THROUGH THIS
CORRIDOR WITH MLCAPE OF AROUND 1000 J/KG /PER 18Z IAD SOUNDING/.
THIS AIR MASS DESTABILIZATION IN COMBINATION WITH CONVERGENCE ALONG
THE ADVANCING COLD FRONT AND INCREASED LARGE-SCALE FORCING FOR
ASCENT ARE CONTRIBUTING TO INTENSIFYING DEEP...MOIST CONVECTION IN A
BROKEN BAND FROM ERN PA INTO THE ERN CAROLINAS. THIS ACTIVITY
SHOULD CONTINUE TO INTENSIFY/ORGANIZE THROUGH THE REMAINDER OF THE
AFTERNOON AS MORE PERSISTENT UPDRAFTS ARE MODULATED BY THE STRONG
VERTICAL SHEAR /I.E. EFFECTIVE BULK SHEAR OF 60-70 KT/. WHILE THE
POTENTIAL FOR A TORNADO OR TWO WILL EXIST WITH ANY MORE INTENSE
STORMS EMBEDDED WITHIN OR FORMING IN ADVANCE OF THE LINE...THE
CORRIDOR FROM THE DELMARVA NWD INTO THE LOWER HUDSON VALLEY WILL
LIKELY EXPERIENCE THE HIGHEST THREAT. HERE...SURFACE WINDS WILL
REMAINED BACKED WITHIN ZONE OF STRONG ISALLOBARIC FORCING ATTENDANT
TO MIGRATORY SURFACE LOW WITH 0-1 KM SHEAR OF 35-40 KT.
OTHERWISE...EXPECT LOCALLY DAMAGING WIND GUSTS TO REMAIN THE PRIMARY
SEVERE WEATHER THREAT WITH THE EVOLVING CONVECTIVE LINE SEGMENTS.
THE GREATEST SEVERE POTENTIAL WILL LIKELY BEGIN TO DIMINISH BY LATER
THIS EVENING AS COLD FRONT MOVES OFF THE MID ATLANTIC COAST. SOME
THREAT FOR LOCALLY DAMAGING WIND GUSTS MAY STILL CONTINUE ACROSS SRN
PARTS OF NEW ENGLAND OVERNIGHT...HOWEVER FORECAST SOUNDINGS SUGGEST
THAT ANY ONGOING STORMS WILL LIKELY BE SLIGHTLY ELEVATED ABOVE A
SHALLOW NEAR SURFACE INVERSION.
..MEAD.. 11/15/2008
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