SWODY2
SPC AC 250555
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 PM CST SAT NOV 24 2007
VALID 261200Z - 271200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NERN GULF
COAST...
..THERE IS A SLGT RISK OF SVR TSTMS OVER FAR NERN SC...ERN NC AND
SERN VA...
..SYNOPSIS...
DYNAMIC MID-LEVEL TROUGH INITIALLY OVER THE ARKLATEX IS FORECAST TO
DEAMPLIFY WHILE RAPIDLY TRANSLATING NEWD THROUGH THE TN
VALLEY...CNTRL APPALACHIANS AND EVENTUALLY INTO NEW ENGLAND BY
TUESDAY MORNING. IN THE LOW LEVELS...ATTENDANT SURFACE LOW OVER WRN
KY WILL CONCURRENTLY DEVELOP NEWD INTO THE UPPER OH VALLEY BY MONDAY
EVENING AND INTO NEW ENGLAND BY 27/12Z. MEANWHILE... TRAILING COLD
FRONT INITIALLY FROM THE LOW PRESSURE CENTER SWD INTO WRN AL WILL
PUSH EWD INTO THE PIEDMONT BY MONDAY EVENING AND OFFSHORE BY TUESDAY
MORNING. THIS BOUNDARY WILL BE THE PRIMARY FOCUS FOR STRONG TO
SEVERE TSTM DEVELOPMENT DURING THE DAY TWO PERIOD.
..NERN GULF COAST...
A PRE-FRONTAL BAND OF TSTMS IS EXPECTED TO BE ONGOING MONDAY MORNING
OVER WRN AL WITHIN ZONE OF STRONG...DEEP LAYER FORCING FOR ASCENT
ASSOCIATED WITH UPPER TROUGH OVER THE LOWER MS VALLEY. WHILE THIS
STRONGER FORCING FOR ASCENT WILL QUICKLY LIFT NEWD THROUGH THE SRN
AND CNTRL APPALACHIANS...SUSTAINED LOW-LEVEL CONVERGENCE ALONG COLD
FRONT SHOULD SUSTAIN TSTM LINE EWD INTO GA AND THE ERN FL PNHDL BY
MONDAY AFTERNOON. DESPITE WEAK WARM SECTOR LAPSE RATES /I.E. NEAR
MOIST ADIABATIC/...BOUNDARY LAYER DEWPOINTS IN THE 60S AND DAYTIME
HEATING WILL CONTRIBUTE TO MLCAPES OF 500-1000 J/KG ACROSS THE
SLIGHT RISK AREA.
FORECAST SOUNDINGS INDICATE 40-45 KT OF DEEP...SWLY SHEAR...
SUPPORTIVE OF ORGANIZED/ROTATING UPDRAFTS CAPABLE OF DAMAGING WINDS
AND PERHAPS A TORNADO OR TWO. THE STRONGEST LOW-LEVEL SHEAR WILL
EXIST THROUGH THE MORNING INTO EARLY AFTERNOON WITH A GENERAL
DECREASE THEREAFTER AS LOW-LEVEL WINDS AHEAD OF FRONT BEGIN TO VEER.
AS THIS PROCESS OCCURS...CONVERGENCE ALONG FRONT AND STORM
INTENSITY MAY TEND TO DIMINISH WITH THE GREATER SEVERE THREAT
BECOMING FOCUSED OVER THE PIEDMONT AND COASTAL PLAIN OF THE
CAROLINAS MONDAY EVENING.
..CAROLINAS INTO SERN VA...
STRENGTHENING SLY LOW-LEVEL FLOW E OF THE APPALACHIANS WILL ERODE OR
FORCE A RAPID RETREAT OF WEDGE FRONT WITH DEWPOINT INCREASING
THROUGH THE 60S OVER THE COASTAL PLAIN AND ERN PORTIONS OF THE
PIEDMONT. LATEST SHORT TERM MODEL GUIDANCE REMAINS RELATIVELY
CONSISTENT IN INDICATING THAT ONGOING...PRE-FRONTAL TSTMS WILL
INTENSIFY MONDAY EVENING AND MONDAY NIGHT AS SRN FRINGE OF HEIGHT
FALL CENTER ASSOCIATED WITH DE-AMPLIFYING UPPER TROUGH OVERSPREADS
WRN EDGE OF LOW-LEVEL MOISTURE AXIS.
IT APPEARS THAT CONVECTIVE INSTABILITY WILL REMAIN QUITE WEAK OVER
THE PIEDMONT...WITH A GENERAL INCREASE TOWARD THE COAST WHERE RICHER
BOUNDARY LAYER MOISTURE WILL CONTRIBUTE TO MLCAPES APPROACHING
500-700 J/KG. THERE IS SOME UNCERTAINTY AS TO THE N/NE EXTENT THAT
SURFACE-BASED INSTABILITY WILL DEVELOP...THOUGH IT DOES APPEAR THAT
THERMODYNAMIC ENVIRONMENT SHOULD SUPPORT STORMS ROOTED IN THE
BOUNDARY LAYER OVER SERN VA.
WIND FIELDS...BOTH IN THE LOW-LEVELS AND THROUGH A DEEP LAYER...WILL
BE QUITE STRONG AND THE POTENTIAL WILL EXIST FOR EMBEDDED SUPERCELL
AND BOWING STRUCTURES DESPITE THE MARGINAL INSTABILITY. DAMAGING
WINDS APPEARS TO BE THE PRIMARY SEVERE WEATHER HAZARD GIVEN FORECAST
STORM MOTIONS OF 40-50 KT. HOWEVER...ISOLATED TORNADOES WILL ALSO
BE POSSIBLE WITH ANY SUPERCELLS THAT CAN DEVELOP AND BECOME
SUSTAINED.
.MEAD.. 11/25/2007
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