National Weather Service United States Department of Commerce
Day 1 Convective Outlook issued at 0542 UTC 4 March 2008
SPC AC 040542
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1142 PM CST MON MAR 03 2008
   
   VALID 041200Z - 051200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PORTION OF THE
   SERN CONUS AND ATLANTIC COASTAL STATES...
   
   ...SYNOPSIS...
   UPPER SHORT-WAVE TROUGH AND EMBEDDED CLOSED LOW -- WHICH SHOULD
   CROSS THE LOWER MS VALLEY EARLY IN THE PERIOD...WILL CONTINUE MOVING
   ENEWD ACROSS THE SOUTHEAST QUARTER OF THE CONUS WHILE TAKING ON AN
   INCREASINGLY NEGATIVE TILT.  THE TROUGH WILL BE ACCOMPANIED BY A
   STRONG DEEP-LAYER WIND FIELD...WHICH WILL SPREAD ACROSS THE ERN
   CONUS IN ADVANCE OF THIS FEATURE.  
   
   AT THE SURFACE...A SLOWLY-DEEPENING LOW INITIALLY FORECAST INVOF
   MIDDLE TN WILL MOVE NEWD WITH TIME...REACHING ERN PA AND VICINITY BY
   THE END OF THE PERIOD.  ASSOCIATED COLD FRONT WILL SWEEP ACROSS THE
   APPALACHIANS AND THE SOUTHEAST CONUS...LIKELY REACHING THE
   MID-ATLANTIC COAST BY 05/12Z.
   
   ...SOUTHEAST U.S. NEWD INTO THE MID-ATLANTIC REGION...
   WIDESPREAD PRECIPITATION IS FORECAST TO SPREAD EWD ACROSS THE ERN
   THIRD OF THE CONUS THIS PERIOD...AHEAD OF APPROACHING UPPER TROUGH
   AND ASSOCIATED SURFACE FRONT.  WHILE PRE-FRONTAL ENVIRONMENT FROM
   THE SERN U.S. TO THE ATLANTIC COAST STATES WILL FEATURE A MOIST
   BOUNDARY LAYER BUT WEAK LAPSE RATES ALOFT -- AND THUS ONLY MARGINAL
   INSTABILITY...STRONG DEEP-LAYER FLOW SPREADING ACROSS THE REGION
   WITH TIME WILL SUPPORT A THREAT FOR ORGANIZED/SEVERE CONVECTION.
   
   INITIAL SEVERE THREAT IS EXPECTED ACROSS ERN AL/GA AND THE FL
   PANHANDLE...AND PERHAPS INTO PARTS OF ERN TN.  WHILE A COMBINATION
   OF LINEAR AND CELLULAR STORM MODES ARE EXPECTED...ROTATING UPDRAFTS
   ARE ANTICIPATED WITH EITHER MODE...ALONG WITH ASSOCIATED THREAT FOR
   ISOLATED TORNADOES AND DAMAGING WINDS.
   
   STORMS SHOULD SPREAD ACROSS GA AND INTO THE CAROLINAS/WRN VA THROUGH
   THE AFTERNOON.  WHILE HIGHLY-SHEARED ENVIRONMENT WILL
   PERSIST...DAYTIME HEATING -- AND THUS ANY ADDITIONAL DESTABILIZATION
   -- SHOULD REMAIN LIMITED.  HOWEVER...SHEAR WILL REMAIN SUPPORTIVE OF
   TORNADOES...WITH DAMAGING WINDS ALSO EXPECTED DEPENDING UPON
   DOMINANT STORM MODE.  
   
   OVERNIGHT...STRONGEST FLOW ALOFT IS FORECAST TO SPREAD ATOP THE WARM
   SECTOR ACROSS VA AND VICINITY...AS THE NEGATIVELY-TILTING UPPER
   FEATURE NEARS THE SURFACE WARM SECTOR.  THUS -- DESPITE WHAT SHOULD
   BE A MINIMALLY-UNSTABLE AIRMASS...INCREASING FLOW ATOP THE SURFACE
   LOW/FRONT SHOULD SUPPORT A STRONGLY-FORCED LINE OF CONVECTION WITH
   EMBEDDED ROTATION -- AND THUS A THREAT FOR DAMAGING WINDS AND
   TORNADOES MAY PERSIST THROUGH THE END OF THE PERIOD INTO THE
   MID-ATLANTIC REGION.
   
   ..GOSS/HURLBUT.. 03/04/2008
   
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