SWODY3
SPC AC 250744
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0144 AM CST TUE DEC 25 2007
VALID 271200Z - 281200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LOWER MS
VALLEY REGION....
..SYNOPSIS...
GFS...NAM...AND SREF GUIDANCE ARE IN VERY GOOD AGREEMENT MOVING
STRONG UPPER SHORT WAVE TROUGH FROM THE SRN ROCKIES TOWARD THE LOWER
MO RIVER VALLEY BY THE END OF THE PERIOD. ASSOCIATED SURFACE LOW IS
FORECAST TO MOVE ACROSS THE SRN PLAINS THEN REDEVELOP NEWD INTO THE
MIDDLE MS VALLEY DURING THE OVERNIGHT HOURS. EARLIER FRONT OVER THE
NRN/WRN GULF IS EXPECTED TO LIFT NWD TO THE TX/LA COAST DURING THE
DAY IN RESPONSE TO DEVELOPING SURFACE PRESSURE FALLS OVER THE SRN
PLAINS/LOWER MS VALLEY...THEN CONTINUE INLAND REACHING A NWRN
AL/SERN TX LINE DURING THE NIGHT. A COLD FRONT MOVING ACROSS THE
SRN PLAINS IS FORECAST TO PROGRESS EWD REACHING A LINE FROM THE
MIDDLE MS VALLEY TO THE TX COAST BY THE END OF THE PERIOD.
..SERN TX/LA/MS/WRN AL...
LOW LEVEL MOISTURE RETURNING NWD FROM THE NRN GULF WILL SPREAD
LOW/MID 60S SURFACE DEW POINTS INTO PARTS OF SERN TX/SRN LA/SERN
MS/SRN AL/NWRN FL THURSDAY NIGHT...WITH MID 50S DEW POINTS AS FAR
NORTH AS CENTRAL PARTS OF LA/MS AND NRN AL. THIS WILL CONTRIBUTE TO
NOCTURNAL DESTABILIZATION WITH MUCAPE OF 500-1000 J/KG ACROSS THE
AREA.
INTENSE DYNAMIC FORCING FOR LARGE SCALE ASCENT WILL OVERSPREAD THE
RETURNING MOISTURE/INSTABILITY FIELD FROM THE WEST STARTING IN THE
LATE AFTERNOON AND CONTINUING THROUGH THE OVERNIGHT HOURS IN
ASSOCIATION WITH THE STRONG UPPER LEVEL JET STREAM FROM TX INTO THE
TN VALLEY. DIVERGENCE ALOFT WITHIN THE RIGHT ENTRANCE REGION OF THE
140 KT JET STREAK COUPLED WITH STRONG LOW LEVEL THETA-E ADVECTION
ASSOCIATED WITH A DEVELOPING 50-60 KT LOW LEVEL JET WILL FOCUS
THUNDERSTORM DEVELOPMENT ALONG AN AXIS FROM SERN TX/SWRN LA ACROSS
CENTRAL/SRN MS INTO NWRN/WEST CENTRAL AL THURSDAY NIGHT. FORECAST
SOUNDINGS SHOW WINDS THAT VEER AND INCREASE WITH HEIGHT RESULTING IN
LARGE CYCLONICALLY CURVED LOW LEVEL HODOGRAPHS AND STRONG LOW- AND
DEEP-LAYER SHEAR. THIS WILL SUPPORT STRONG/SEVERE THUNDERSTORM
DEVELOPMENT DURING THE NIGHT INCLUDING POTENTIAL FOR A FEW
SUPERCELLS...ESPECIALLY OVER SRN PARTS OF THE AREA WHERE HIGHER DEW
POINTS/INSTABILITY WILL BE PRESENT.
.WEISS.. 12/25/2007
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