DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 121921
SWODY1
SPC AC 121919

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0219 PM CDT TUE MAR 12 2013

VALID 122000Z - 131200Z

...NO SVR TSTM AREAS FORECAST...

...SERN VA AND ERN NC...
AFTERNOON SURFACE ANALYSIS SHOWS A MESO LOW ADVANCING NWD TOWARD NEW
ENGLAND...WITH A COLD FRONT EXTENDING SWD INTO ERN VA/NC. DRY AIR IN
THE MIDLEVELS HAS SPREAD ACROSS THE COLD FRONT...WHICH HAS CLEARED
OUT CLOUD COVER ASSOCIATED WITH THE WARM CONVEYOR BELT. THIS
CLEARING HAS ALLOWED SURFACE TEMPERATURES TO WARM INTO THE MID 60S.
IN ADDITION...AXIS OF LOW 60S DEWPOINTS EXTENDS NWD
ALONG/IMMEDIATELY AHEAD OF THE FRONT INTO ERN VA. NARROW ZONE OF
DESTABILIZATION HAS DEVELOPED AS A RESULT...WITH MLCAPE INCREASING
TO AROUND 300 J/KG OVER SERN VA AND ERN NC. THIS ENVIRONMENT HAS
SUPPORTED THE DEVELOPMENT OF SEVERAL BROKEN LINES OF CONVECTION
PRODUCING ISOLATED SPORADIC LIGHTNING. AREA VWP/S AND RAP GUIDANCE
INDICATE DEEP-LAYER VERTICAL WIND SHEAR AROUND 50 KT IS FAVORABLE
FOR ORGANIZED THUNDERSTORM DEVELOPMENT. HOWEVER...LOW-LEVEL FLOW HAS
VEERED/WEAKENED DURING THE PAST FEW HOURS. THIS WEAKENING COMBINED
WITH THE VERY MARGINAL BUOYANCY IS EXPECTED TO PRECLUDE A SVR
WEATHER THREAT AS CONVECTION ADVANCES TOWARD THE COAST THROUGH LATE
AFTERNOON.

..GARNER.. 03/12/2013

.PREV DISCUSSION... /ISSUED 1119 AM CDT TUE MAR 12 2013/

...SYNOPSIS...
DOWNSTREAM OF BROAD AND FAIRLY AMPLIFIED ANTICYCLONIC UPPER
FLOW...CURVING FROM THE EASTERN PACIFIC THROUGH THE ROCKIES...UPPER
TROUGHING OVER THE EASTERN U.S. APPEARS LIKELY TO AMPLIFY FURTHER AS
A SIGNIFICANT SHORT WAVE IMPULSE DIGS WITHIN CYCLONIC FLOW ACROSS
THE MID MISSOURI VALLEY INTO THE LOWER OHIO AND TENNESSEE VALLEYS.
THIS FEATURE IS PRECEDED BY ANOTHER IMPULSE...CURRENTLY IN THE
PROCESS OF PIVOTING AROUND THE EASTERN PERIPHERY OF A BROADER SCALE
CYCLONIC CIRCULATION CENTER OVER THE UPPER MIDWEST/GREAT LAKES
REGION...WHICH IS SUPPORTING THE NORTHEASTWARD MIGRATION OF A
SECONDARY FRONTAL WAVE FROM THE LEE OF THE CENTRAL APPALACHIANS INTO
NEW ENGLAND. WHILE THE FRONT TO THE SOUTH MAY BE SLOW TO PROGRESS
EAST AND SOUTH OF THE SOUTHERN ATLANTIC SEABOARD...INCLUDING THE
FLORIDA PENINSULA...MODELS SUGGEST NO SIGNIFICANT ADDITIONAL WAVE
DEVELOPMENT ALONG THE FRONT THROUGH THE REMAINDER OF THIS PERIOD.
LOW PROBABILITIES FOR THUNDERSTORM ACTIVITY DO APPEAR TO LINGER
ACROSS PARTS OF SOUTHERN MID ATLANTIC COAST FOR TODAY...BUT THE
EVOLVING LARGE-SCALE PATTERN ACROSS THE U.S. GENERALLY FAVORS THE
MAINTENANCE OF STABLE CONDITIONS WITH NEGLIGIBLE CONVECTIVE
POTENTIAL.

...SOUTHERN MID ATLANTIC COASTAL AREAS...
WITH THE FRONTAL WAVE QUICKLY BEGINNING TO LIFT NORTHEAST OF THE MID
ATLANTIC COAST REGION...PRE-FRONTAL LOW-LEVEL HODOGRAPHS ACROSS
EASTERN VIRGINIA AND THE CAROLINAS ARE IN THE PROCESS OF SHRINKING
AND BECOMING MORE LINEAR. ADDITIONALLY...IN THE WAKE OF INITIAL
CONVECTION NOW SPREADING FROM NORTHERN MID ATLANTIC COASTAL AREAS
TOWARD SOUTHERN NEW ENGLAND...AND EASTWARD ACROSS THE OUTER BANKS
AREA OF NORTH CAROLINA...MID-LEVEL DRYING AND WARMING ASSOCIATED
WITH SUBSIDENCE WILL TEND TO CAP THE RESIDUAL MOIST PRE-FRONTAL
SURFACE ENVIRONMENT ACROSS THE PIEDMONT INTO PORTIONS OF THE COASTAL
PLAIN. SO THE WINDOW OF OPPORTUNITY FOR SUBSTANTIVE THUNDERSTORM
DEVELOPMENT PRIOR TO FRONTAL PASSAGE SEEMS SMALL...AND PERHAPS
CONFINED TO THE NORFOLK AREA OF SOUTHEAST VIRGINIA...SOUTHWARD INTO
THE PARTS OF THE NORTH CAROLINA COASTAL PLAIN AND OUTER BANKS
AREA...GENERALLY DURING THE 18-21Z TIME FRAME. EVEN IF THIS
MATERIALIZES...SEVERE WEATHER POTENTIAL STILL SEEMS VERY LOW TO
NEGLIGIBLE.

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