The Palm Sunday, March 28, 2010, Severe Thunderstorm Outbreak

SPC AC 271730
   
DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT SAT MAR 27 2010
   
VALID 281200Z - 291200Z
   
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE SOUTHEAST
STATES/CAROLINAS...
   
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE FL PENINSULA...
   
...SYNOPSIS...
BROAD LONGWAVE TROUGH WILL MIGRATE EASTWARD GENERALLY FROM THE MS
RIVER VALLEY TO THE APPALACHIANS ON SUNDAY. THE BRUNT OF THE CYCLONE
WILL TRANSITION EAST-NORTHEASTWARD OVER THE OH/TN RIVER
VALLEYS...WITH LARGE SCALE HEIGHT FALLS ASSOCIATED WITH A SOUTHERN
STREAM/BASAL SHORTWAVE TROUGH AND THE POSSIBILITY OF SECONDARY
SURFACE CYCLOGENESIS ACROSS THE SOUTHEAST STATES/CAROLINAS SUNDAY
AFTERNOON/NIGHT.
   
...SOUTHEAST STATES/CAROLINAS...
LIMITED MOISTURE RETURN/QUALITY WILL LIKELY PRECLUDE A MORE
SUBSTANTIAL SEVERE EPISODE ACROSS THE SOUTHEAST STATES/CAROLINAS ON
SUNDAY...BUT RATHER STRONG DEEP LAYER FLOW FIELDS/RELATIVELY STEEP
LAPSE RATES ALOFT WILL SUPPORT A SEVERE RISK...ESPECIALLY ACROSS
PORTIONS OF EASTERN AL/GA TO THE CAROLINAS SUNDAY AFTERNOON/NIGHT.
   
INITIAL UPSWING IN TSTMS/SEVERE POTENTIAL SHOULD OCCUR ALONG/AHEAD
OF AN ADVANCING COLD FRONT...POTENTIALLY IN TANDEM WITH
SECONDARY/MODEST SURFACE CYCLOGENESIS...ACROSS EASTERN AL AND GA
SUNDAY AFTERNOON. MODEST SURFACE DEWPOINTS /UPPER 50S TO LOWER 60S
F/ BUT RELATIVELY STEEP LAPSE RATES ALOFT WILL GENERALLY ONLY
SUPPORT WARM SECTOR MLCAPE VALUES OF 500-750 J/KG OR LESS. BUT EVEN
WITH A WEAK BUOYANCY REGIME...STRONG LOW TO MID TROPOSPHERIC FLOW
INCLUDING 30-40 KT AROUND 1 KM WILL CONTRIBUTE TO MORE THAN ADEQUATE
SHEAR PROFILES/HODOGRAPHS FOR SUPERCELLS/SMALL BOWS CAPABLE OF
DAMAGING WINDS/POSSIBILITY OF A FEW TORNADOES...ALONG WITH SEVERE
HAIL ESPECIALLY VIA INITIAL AND/OR QUASI-DISCRETE DEVELOPMENT. AT
LEAST AN ISOLATED SEVERE THREAT SHOULD TRANSITION EAST-NORTHEASTWARD
SUNDAY EVENING/NIGHT ACROSS PORTIONS OF THE CAROLINAS.
   
...FL PENINSULA...
MULTI-EPISODE/MAJORITY OF THE PERIOD SEVERE POTENTIAL WILL LIKELY
EXIST ACROSS THE FL PENINSULA...AND REGION APPEARS TO WARRANT A
CATEGORICAL SLIGHT RISK. SEVERE THREAT MAY INITIALLY INCREASE DURING
THE AFTERNOON...EITHER VIA INLAND ADVANCEMENT OR PERIPHERAL
DEVELOPMENT OF EARLY DAY GULF OF MEXICO TSTMS. THIS MAY ESPECIALLY
BE ACROSS THE NORTH CENTRAL FL PENINSULA AMIDST AN INCREASINGLY
MOIST/WEAKLY CAPPED BOUNDARY LAYER...WHERE VERTICAL SHEAR PROFILES
WOULD SUPPORT SOME SUPERCELLS.
   
ADDITIONALLY...AS AN UPSTREAM SHORTWAVE TROUGH CROSSES THE GULF
COAST AND THE POLAR/SUBTROPICAL JETS COME INTO PHASE SUNDAY
NIGHT...STRENGTHENING DEEP LAYER SHEAR /WHILE A CONTINUALLY
MOISTENING BOUNDARY LAYER/ AMIDST A STRONGLY DIFFLUENT REGIME COULD
ALSO SUPPORT A NOCTURNAL RISK FOR SOME SUPERCELLS/BOWS WITH A
DAMAGING WIND/TORNADO RISK.
   
...TN/OH RIVER VALLEYS TO THE APPALACHIANS...
AS THE PARENT SHORTWAVE TROUGH/SURFACE LOW MOVEMENT LARGELY
PARALLELS THE OH RIVER....ONLY LIMITED BOUNDARY LAYER MOISTURE
/SURFACE DEWPOINTS GENERALLY UPPER 40S TO PERHAPS LOWER 50S F/ WILL
EXIST IN THE PRE-COLD FRONT/OCCLUSION WARM SECTOR. HOWEVER...AMPLE
VERTICAL SHEAR AND MODEST SURFACE HEATING COUPLED WITH STEEP LAPSE
RATES ALOFT COULD SUPPORT SOME STRONG/SEVERE TSTMS CAPABLE OF
HAIL/GUSTY WINDS AND PERHAPS A BRIEF TORNADO...MAINLY SUNDAY
AFTERNOON. GIVEN THE POSSIBILITY/DEGREE OF EARLY DAY CLOUD
COVER/SHOWERY PRECIPITATION...AFOREMENTIONED LIMITED MOISTURE/WEAK
BUOYANCY PRECLUDES A CATEGORICAL SLIGHT RISK AT THIS TIME.
   
..GUYER.. 03/27/2010
   
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z