SPC AC 010549
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1149 PM CST SAT FEB 28 2009
VALID 011200Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
VERY STRONG STORM SYSTEM ALOFT -- PROGGED TO BE CENTERED OVER AL AT
THE START OF THE PERIOD...WILL MOVE ENEWD/NEWD ACROSS THE SOUTHEAST
U.S. REACHING ERN NC/ERN VA LATE. AS THIS OCCURS...AN ASSOCIATED
SURFACE LOW INVOF GA COAST EARLY SHOULD SHIFT QUICKLY NNEWD ALONG
THE ATLANTIC COAST...REACHING COASTAL NC BY 02/00Z. THE TRAILING
COLD FRONT MOVING SWD THROUGH THE DAY ACROSS FL SHOULD CLEAR THE
PENINSULA/KEYS BY LATE AFTERNOON...ENDING THE CONVECTIVE THREAT
ACROSS THE SOUTHEAST CONUS.
AS THIS STRONG STORM SYSTEM CROSSES THE SOUTHEAST...A LARGER-SCALE
AMPLIFICATION IN THE UPPER PATTERN IS FORECAST. AS A TROUGH OVER
ERN CANADA PHASES WITH THE SOUTHEASTERN U.S. FEATURE RESULTING IN A
LARGE/SHARP LONGER-WAVE FEATURE...A RIDGE WILL AMPLIFY NWD ACROSS
THE U.S. AND CANADIAN ROCKIES AHEAD OF A SECOND LARGE TROUGH
CROSSING THE ERN PACIFIC AND APPROACHING WRN NOAM. CONVECTION WILL
AFFECT THE W COAST STATES IN CONJUNCTION WITH THIS FEATURE...BUT
OTHERWISE RELATIVELY TRANQUIL WEATHER IS FORECAST ACROSS A LARGE
PORTION OF THE INTERIOR CONUS THROUGH THE PERIOD.
...COASTAL PORTIONS OF GA AND THE CAROLINAS...
A NARROW ZONE OF AMPLE MOISTURE/INSTABILITY TO SUPPORT STRONGER
CONVECTION WILL SHIFT NEWD ALONG THE SERN U.S. ATLANTIC
COAST...IMMEDIATELY E/NE OF A SURFACE LOW PROGGED TO CROSS THIS
REGION. ATTM...QUESTIONS REMAIN AS TO WHETHER THIS LOW -- AND
ASSOCIATED WARM SECTOR -- WILL REMAIN OFFSHORE OR POSSIBLY JUST
INLAND. WITH BACKED LOW-LEVEL FLOW IN THE NERN QUADRANT OF THIS LOW
BENEATH STRONG SWLY FLOW ALOFT...SHEAR WOULD BE SUPPORTIVE OF
ORGANIZED/SUPERCELL STORMS. IF THE WARM SECTOR -- AND AMPLE
INSTABILITY -- CAN REMAIN INLAND ACROSS COASTAL GA AND THE
CAROLINAS...AT LEAST SOME SEVERE STORM/TORNADO POTENTIAL WOULD
EXIST. ATTM HOWEVER...WITH MOST IF NOT ALL OF THE MORE FAVORABLE
AIRMASS TO REMAIN OFFSHORE -- PARTICULARLY AFTER THE FIRST COUPLE OF
HOURS OF THE PERIOD -- WILL MAINTAIN ONLY LOW SEVERE PROBABILITY
ACROSS A NARROW SLIVER OF THE SERN ATLANTIC COAST.
...SERN FL...
WEAK LAPSE RATES/LIMITED INSTABILITY AND MODEST SHEAR SHOULD
CHARACTERIZE THE WARM SECTOR ACROSS FL AHEAD OF THE SEWD-MOVING
FRONT. WHILE SHOWERS AND OCCASIONAL LIGHTNING WILL LIKELY ACCOMPANY
THE FRONT THROUGH THE MORNING...DEEPER CONVECTION/MORE WIDESPREAD
THUNDERSTORMS MAY EVOLVE DURING THE AFTERNOON AHEAD OF THE BOUNDARY
AS IT MOVES INTO SERN FL. THOUGH OVERALL SEVERE THREAT SHOULD BE
LIMITED...A STRONGER GUST OR TWO CANNOT BE RULED OUT...BEFORE
CONVECTION MOVES OFFSHORE LATE IN THE DAY.
..GOSS.. 03/01/2009
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