SWODY2
SPC AC 121726
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1126 AM CST WED DEC 12 2007
VALID 131200Z - 141200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
A COMPLEX SPLIT UPPER FLOW CONTINUES...FROM THE PACIFIC...THROUGH
MUCH OF NORTH AMERICA...INTO THE SOUTHEASTERN PERIPHERY OF A
NORTHEASTERN CANADIAN POLAR VORTEX. PERHAPS MOST PROMINENT TO THE
U.S...IS A SPLIT BELT EMANATING FROM THE NORTHERN PACIFIC...WITH A
SERIES OF EMBEDDED SHORT WAVE IMPULSES DIGGING INTO/THROUGH A
SOUTHERN BRANCH TROUGH OVER THE SOUTHWESTERN STATES...AND A MORE
ZONAL STREAM ACROSS THE NORTHERN TIER STATES.
IN PARTICULAR...MODELS INDICATE THAT ONE SIGNIFICANT SHORT WAVE
TROUGH...NOW DIGGING TO THE LEE OF THE CANADIAN ROCKIES...WILL
CONTINUE THROUGH THE UPPER MISSISSIPPI VALLEY BY 12Z THURSDAY...AND
ACROSS THE GREAT LAKES INTO NORTHERN NEW ENGLAND BY 12Z FRIDAY.
THIS FEATURE HAS CONTRIBUTED TO THE NORTHEASTWARD ACCELERATION OF A
SIGNIFICANT SOUTHERN STREAM IMPULSE...WHICH IS BECOMING INCREASINGLY
SHEARED AS IT LIFTS NORTHEAST OF THE SOUTHERN ROCKIES. REMNANTS OF
THE LATTER SYSTEM ARE PROGGED TO MOVE RAPIDLY THROUGH THE OHIO
VALLEY EARLY THURSDAY...BEFORE CONTINUING OFF NORTHERN/MID ATLANTIC
COASTAL AREAS THURSDAY EVENING. AS THIS OCCURS...AND A WEAK
TROPICAL SYSTEM CONTINUES WESTWARD THROUGH THE CARIBBEAN...THE
SEASONABLY STRONG SUBTROPICAL RIDGE OVER THE SOUTHEAST IS EXPECTED
TO FINALLY WEAKEN. AND...IN CONJUNCTION WITH FORCING ASSOCIATED
WITH THE SOUTHERN BRANCH IMPULSE...WEAK WAVE DEVELOPMENT MAY OCCUR
ALONG A SURFACE FRONT...TO THE WEST OF THE CENTRAL APPALACHIANS BY
EARLY THURSDAY...AND NEAR/EAST OF NORTHERN MID ATLANTIC COASTAL
AREAS LATER THURSDAY/THURSDAY NIGHT.
..NRN GULF/SOUTH ATLANTIC COAST STATES INTO NEW ENGLAND...
WITH THE SUPPRESSION OF GULF MOISTURE RETURN...AND A SHRINKING MOIST
WARM SECTOR DUE TO COLD INTRUSIONS TO THE LEE OF THE SOUTHERN
ROCKIES...AND THE NORTHERN/CENTRAL APPALACHIANS... CONVECTIVE
POTENTIAL DURING THIS PERIOD IS LOW. BUT...MOISTURE LEVELS WILL
REMAIN RELATIVELY MODEST AT LEAST INTO EARLY THURSDAY...AHEAD OF A
COLD FRONT ADVANCING INTO THE EASTERN GULF STATES/UPPER TENNESSEE
VALLEY/CENTRAL APPALACHIANS. AS THIS AIR IS LIFTED IN A STRONG
LOW/MID TROPOSPHERIC WARM ADVECTION REGIME...NORTHEAST OF THE
DEVELOPING WEAK SURFACE CYCLONE ACROSS THE UPPER OHIO
VALLEY...SUFFICIENT DESTABILIZATION IS EXPECTED FOR CONVECTIVE
DEVELOPMENT. ALTHOUGH MOST UNSTABLE CAPE ABOVE THE WARM FRONTAL
INVERSION LAYER IS GENERALLY ONLY PROGGED AROUND 100 J/KG OR
LESS...FORECAST SOUNDINGS SUGGEST THAT IT WILL EXTEND THROUGH THE
FAVORABLE MIXED PHASE LAYER FOR CHARGE SEPARATION/ CLOUD
ELECTRIFICATION. THUS...A FEW WEAK THUNDERSTORMS APPEAR
POSSIBLE...MOSTLY DURING THE 13/12-21Z TIME FRAME...BEFORE SECONDARY
SURFACE LOW DEVELOPMENT OCCURS OFF THE NORTHERN MID ATLANTIC COAST.
..FLORIDA PENINSULA...
DESTABILIZATION IS EXPECTED ACROSS SOUTHEASTERN COASTAL AREAS AND
THE KEYS...ASSOCIATED WITH THE INFLUX OF TROPICAL BOUNDARY LAYER
MOISTURE TO THE NORTHEAST OF OLGA. AND...AS MID/UPPER SUBTROPICAL
RIDGE WEAKENS...POTENTIAL FOR SCATTERED THUNDERSTORM ACTIVITY IS
EXPECTED TO INCREASE BY LATE THURSDAY/THURSDAY NIGHT.
.KERR.. 12/12/2007
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