SPC AC 212003
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0303 PM CDT TUE AUG 21 2007
VALID 212000Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF VA AND THE
CAROLINAS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL PLAINS...
...VA/CAROLINAS...
DEEP CONVECTION THAT INITIATED ACROSS THE MOUNTAINS CONTINUES TO
ORGANIZE A SPREAD EAST OVER WRN SECTIONS OF VA AND NC THIS
AFTERNOON. DEEP ASCENT AND STRONG VERTICAL SPEED SHEAR ARE BEING
ENHANCED BY REMNANT TROPICAL VORTEX...NOW MOVING ACROSS ERN
KY...WHICH WAS BECOMING INCREASINGLY ABSORBED INTO DEEP-LAYER WLY
FLOW AROUND NRN PERIPHERY OF SERN U.S. SUBTROPICAL RIDGE. AIR MASS
ACROSS THE PIEDMONT AREAS...SANDHILLS/COASTAL PLAINS OF NC...WAS
VERY HOT AND UNSTABLE. GREATER MOISTURE NEARER THE COAST WAS
BOOSTING CAPE VALUES ACROSS THIS REGION. STORMS MAY FURTHER INCREASE
IN INTENSITY AS GREATER INSTABILITY IS REALIZED. BELT OF 30KT
EFFECTIVE BULK SHEAR...PRIMARILY UNIDIRECTIONAL IN NATURE AND
ACCOMPANYING THE CONVECTION...WILL ENHANCE STORM
ORGANIZATION/PERSISTENCE. LINE SEGMENTS AND PERHAPS A FEW SUPERCELLS
WILL DEVELOP EAST THROUGH EARLY EVENING. DAMAGING WINDS APPEAR MOST
LIKELY AS CONVECTION SPREADS ATOP HOT AND DEEPLY MIXED BOUNDARY
LAYER OVER THE NEXT SEVERAL HOURS.
...CNTRL PLAINS...
LATEST ANALYSIS DEPICTS SURFACE LOW ALONG THE SD/NEB BORDER WITH
DRYLINE/THERMAL TROUGH EXTENDING SSWWD ACROSS CNTRL NEB TO CO/KS
BORDER. WHILE AIR MASS PRECEEDING THESE FEATURES REMAINS
CAPPED...INTENSE SURFACE HEATING AND HIGH THETA-E WERE CONTRIBUTING
TO VERY STRONG DESTABILIZATION WITH MLCAPE CURRENTLY EXCEEDING 4000
J/KG ON LATEST OBJECTIVE ANALYSIS FIELDS IN SCNTRL NEB.
CONTINUED HEATING AND LOW LEVEL CONVERGENCE ARE EXPECTED TO OVERCOME
CONVECTIVE INHIBITION AND RESULT IN RAPID TSTM DEVELOPMENT LATE THIS
AFTERNOON THROUGH THIS EVENING...MOST LIKELY BETWEEN 21Z-00Z. THIS
PROCESS MAY BE AIDED ACROSS SD/NEB AND NWRN IA AREAS ALONG SRN
FRINGE OF STRONG LOW-AMPLITUDE IMPULSE NOW MOVING ACROSS THE
DAKOTAS. WLY FLOW/MID LEVEL JET ASSOCIATED WITH THIS IMPULSE ATOP
SSELY SURFACE WILL LEAD TO SUFFICIENT SHEAR FOR SUPERCELLS.
FURTHERMORE...CORRIDOR OF LOCALLY ENHANCED LOW LEVEL SHEAR AND HIGH
BOUNDARY LAYER RH...FROM SURFACE LOW ESEWD ALONG RESIDUAL
OUTFLOW/FRONT ACROSS WRN IA...MAY RESULT IN GREATER SUPERCELL
TORNADO POTENTIAL IF DISCRETE STORMS CAN TRACK INTO THIS ZONE.
ADDITIONAL ACTIVITY IS LIKELY TO INITIATE ALONG DRYLINE/THERMAL
TROUGH AXIS AS HEATING/MIXING OVERCOMES INHIBITION NEAR THIS
BOUNDARY. THIS ACTIVITY...POTENTIALLY OUTFLOW DOMINANT...WILL LIKELY
POSE A DAMAGING WIND THREAT INTO THIS EVENING.
ONE OR TWO STORM CLUSTERS MAY EVOLVE THROUGH THE EVENING AND SPREAD
GRADUALLY EAST AS LLJ MAINTAINS ASCENT/MASS INFLOW ALONG
WEST-TO-EAST DEEP-LAYER FRONTAL ZONE ACROSS THE PLAINS/MO VALLEY
AREAS.
..CARBIN.. 08/21/2007
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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