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

SPC AC 281259
   
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0759 AM CDT SUN MAR 28 2010
   
VALID 281300Z - 291200Z
  
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SERN
STATES...
   
...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE FL
PENINSULA...
   
...SYNOPSIS...
COMPLEX/POSITIVE-TILT TROUGH NOW OVER THE LWR MS VLY WILL CONTINUE
SLOWLY E THROUGH THE PERIOD AS UPSTREAM RIDGE OVER THE RCKYS 
DEAMPLIFIES AND CONTINUES SE INTO THE PLNS.  THE MS VLY TROUGH WILL
UNDERGO CONSIDERABLE CHANGE DURING THE NEXT 24 HRS.  PRIMARY
ASSOCIATED UPR VORT...NOW OVER NE AR...SHOULD MOVE ENE ACROSS KY
TODAY...BEFORE WEAKENING OVER WRN WV/PA TONIGHT/EARLY MON.  AT THE
SAME TIME...DISTURBANCE NOW IN NE OK SHOULD CONTINUE SE INTO LA
BEFORE CONTINUING E INTO GA BY 12Z MON.  AS A RESULT...THE LARGER
SCALE TROUGH SHOULD ASSUME A MORE NEUTRAL TILT.
   
AT LWR LVLS...COLD/OCCLUDED FRONT SHOULD MOVE STEADILY E ACROSS THE
TN VLY TODAY AND INTO THE SRN APPALACHIANS TONIGHT.  WARM FRONT NOW
BECOMING ESTABLISHED OVER THE NRN GULF OF MEXICO ENE TO OFF THE SC
CST SHOULD BECOME BETTER DEFINED THROUGH THE PERIOD.  THE FRONT MAY
SERVE AS A FOCUS FOR THE DEVELOPMENT OF A SFC WAVE OVER S GA LATE
TODAY OR EARLY TONIGHT.  THIS WAVE SHOULD MOVE E/NE TO THE SC CST
EARLY MON.
   
...AL/GA/SC/NC TODAY THROUGH TONIGHT...
LATEST SFC AND VWP DATA SUGGEST THAT LOW-LVL MOISTURE WILL CONTINUE
TO SLOWLY INCREASE OVER PARTS OF AL/GA AND SC TODAY...AHEAD OF
COLD/OCCLUDED FRONT.  STRENGTHENING LOW-LVL SLY FLOW AND ASSOCIATED
EROSION OF WEDGE AIR MASS...AND MID-LVL COOL ADVECTION...SHOULD
BOOST SBCAPE TO AROUND 500 J/KG WITH EVEN MODEST SFC HEATING.  
   
VERY STRONG /70 KT/ DEEP WSWLY SHEAR WILL EXIST OVER THE REGION AS
AREA WILL LIE BENEATH AXIS OF 100+ KT DIFLUENT UPR-LVL JET
ASSOCIATED WITH APPROACHING UPR TROUGH.  IT APPEARS THAT UPR LVL
FORCING FOR ASCENT /DCVA/ WILL REMAIN FAIRLY WEAK OVER AL/GA/SC
THROUGH MUCH OF THE DAY AS LEAD UPR VORT MOVES NE INTO KY...AND
UPSTREAM VORT ENTERS LA.  THIS MAY LIMIT STORM COVERAGE AND/OR DELAY
DEVELOPMENT THROUGH PART OF THE DAY.  BUT COMBINATION OF SFC HEATING
WITH CONFLUENT LOW-LVL FLOW SHOULD NEVERTHELESS SUPPORT
CLUSTERS/BANDS OF SUSTAINED STORMS/SUPERCELLS FROM ERN AL AND
NRN/CNTRL GA INTO UPSTATE SC AND POSSIBLY S CNTRL NC BY LATER IN THE
DAY.  THESE STORMS MAY PERSIST OR INCREASE IN COVERAGE THIS EVE AS
UVV INCREASES WITH CONTINUED EWD MOTION OF LA UPR VORT.  
   
STRENGTH OF CLOUD-LAYER SHEAR AND COOL AIR ALOFT SUGGEST GOOD CHANCE
FOR LARGE HAIL...ESPECIALLY THIS AFTN AND EARLY TONIGHT FROM ERN AL
INTO GA AND UPSTATE SC.  TORNADOES MAY ALSO OCCUR AS 0-3 KM SRH
INCREASES TO AROUND 250 M2/S2 FROM CNTRL GA INTO THE SAVANNAH RVR
VLY.
     
THE STORMS SHOULD EVOLVE INTO LOOSELY-ORGANIZED CLUSTERS
TONIGHT/EARLY MON...WITH A LIMITED SVR THREAT POSSIBLY CONTINUING
E/NE INTO CSTL SC AND SRN NC INVOF DEVELOPING SFC WAVE.  
   
...CNTRL/SRN FL THIS AFTN THROUGH TONIGHT...  
WSWLY MID/UPR LVL FLOW WILL STRENGTHEN AND SLIGHTLY BACK ACROSS THE
FL PENINSULA THROUGH EARLY MON AS UPSTREAM TROUGH AMPLIFIES AND
CONTINUES EWD.  INTENSIFYING SWLY LLJ AHEAD OF THE TROUGH LIKELY IS
RESPONSIBLE FOR RECENT DEVELOPMENT OF TSTMS ALONG WARM FRONT OVER
THE N CNTRL AND NERN GULF OR MEXICO.  THE LLJ SHOULD  SHIFT E ACROSS
THE FL PENINSULA LATER TODAY/TONIGHT...AND OFF THE ERN FL CST EARLY
MON AS AFOREMENTIONED SFC WAVE REACHES THE SC CSTL WATERS.

THE GULF TSTMS SHOULD MOVE/DEVELOP E ACROSS PARTS OF CNTRL/SRN FL
LATER TODAY...WITH SFC HEATING LIKELY TO INITIATE ADDITIONAL STORMS
AHEAD OF THE GULF ACTIVITY.  EXTRAPOLATION OF SATELLITE AND GPS PW
DATA SUGGESTS THAT FAIRLY SUBSTANTIAL MOISTURE...WITH  PW AOA 1.50
INCHES...WILL OVERSPREAD MOST OF THE FL ALONG AND S OF WARM FRONT. 
COUPLED WITH SFC HEATING...RESULTING DESTABILIZATION SHOULD BOOST
SBCAPE TO AROUND 1000 J/KG.  WITH 50 KT DEEP WLY SHEAR...SUSTAINED
CONVERGENCE ALONG CONVECTIVE OUTFLOW BOUNDARIES AND/OR SEA BREEZE
FRONTS MAY YIELD A FEW SUPERCELLS.  TORNADOES WILL BE POSSIBLE GIVEN
INCREASING MOISTURE AND LOW-LVL VEERING PROFILES...IN ADDITION TO
HIGH WIND AND MARGINALLY SVR HAIL.  
   
STORM OUTFLOW LIKELY WILL STABILIZE PARTS OF CNTRL FL BY EVE.  BUT
CONTINUED LOW LVL MOISTURE INFLOW...AND STRENGTHENING WIND
FIELD/ASCENT ASSOCIATED WITH APPROACH OF UPR TROUGH...SUGGEST THAT
ADDITIONAL TSTMS WILL AFFECT MUCH OF CNTRL AND SRN FL THROUGH 12Z
MON.  THIS ACTIVITY MAY EVOLVE INTO SEVERAL REGENERATIVE
CLUSTERS...WITH EMBEDDED SUPERCELLS/LEWPS POSING A CONTINUING RISK
FOR OVERNIGHT TORNADOES AND DMGG WIND. 
   
...KY/SRN IND...
A THREAT FOR MAINLY SMALL HAIL MAY DEVELOP THIS AFTN OVER PARTS OF
KY AND SRN IND AS COLD AIR ALOFT OVERSPREADS CONFLUENT LOW-LVL MOIST
AXIS ATTENDANT TO IL SFC LOW.
   
..CORFIDI/JEWELL.. 03/28/2010
   
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