SPC AC 031257
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0657 AM CST SAT JAN 03 2009
VALID 031300Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS TODAY FROM SE TX EWD TO SW
AL...
...EXTREME SE TX/SW LA EWD TO SRN AL/WRN FL PANHANDLE TODAY...
THE PRIMARY FEATURE OF INTEREST WILL BE THE ENEWD MOTION OF A MID
LEVEL SHORTWAVE TROUGH FROM SE TX TO THE TN VALLEY BY TONIGHT.
LOW-LEVEL MOISTURE /BOUNDARY LAYER DEWPOINTS IN THE LOW-MID 60S/ IS
RETURNING NWD IN A BROAD SWATH FROM E TX TO SRN AL/SW GA THIS
MORNING. THIS MOISTURE WILL CONTINUE TO SPREAD NWD THROUGH THE DAY
AND INTO TONIGHT IN RESPONSE TO THE EWD DEVELOPMENT OF A REMNANT LEE
CYCLONE FROM WRN KS TO THE MID MS VALLEY...IN ADVANCE OF A SEPARATE
AND LARGER SCALE NRN STREAM TROUGH.
ONE OR MORE CLUSTERS OF THUNDERSTORMS ARE EXPECTED TO FORM THIS
MORNING OVER THE NW GULF/EXTREME SE TX/SW LA AND SPREAD ENEWD ACROSS
MS/AL THROUGH THIS EVENING IN ADVANCE OF THE EJECTING SRN STREAM MID
LEVEL TROUGH. THE SEASONABLY RICH LOW-LEVEL MOISTURE...ALONG WITH
STEEP MID LEVEL LAPSE RATES FROM THE SRN PLAINS...SHOULD RESULT IN
MLCAPE VALUES NEAR 1500 J/KG. THIS INSTABILITY WILL BE SUFFICIENT
FOR AT LEAST MARGINALLY SEVERE HAIL AND STRONG OUTFLOW WINDS WITH
THE MORE INTENSE STORMS. THE SEVERE STORM THREAT WILL BE LOCALLY
GREATER IF/WHERE CLOUD BREAKS ALLOW SURFACE TEMPERATURES TO WARM
INTO THE 70S AND THE STORMS BECOME FULLY ROOTED AT THE SURFACE.
VERTICAL SHEAR WILL NOT BE PARTICULARLY STRONG IN THE WARM SECTOR
DOWNSTREAM FROM THE EJECTING MID LEVEL WAVE /EFFECTIVE BULK SHEAR OF
30-40 KT AND EFFECTIVE SRH AROUND 100 M2/S2/. STILL...THE
COMBINATION OF MODEST VERTICAL SHEAR AND INSTABILITY COULD SUPPORT
ISOLATED STORMS WITH SUPERCELL STRUCTURES AND AN ATTENDANT THREAT
FOR A BRIEF TORNADO THROUGH THIS EVENING.
FARTHER NW...THE THREAT FOR ADDITIONAL THUNDERSTORM DEVELOPMENT WILL
BE MARGINAL ALONG A COLD FRONT FROM CENTRAL/SE MO INTO SE OK LATER
THIS EVENING INTO TONIGHT. LIMITING FACTORS WILL BE ONLY SHALLOW
ASCENT ALONG THE BOUNDARY...INCREASING CONVECTIVE INHIBITION WITH
DIURNAL COOLING AS WELL AS A RESIDUAL WARM ELEVATED MIXED
LAYER...AND THE RICHEST LOW-MID LEVEL MOISTURE PLUME LOCATED WELL SE
OF THIS AREA.
..THOMPSON.. 01/03/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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