SWODY2
SPC AC 200659
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CST WED FEB 20 2008
VALID 211200Z - 221200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF ERN TX INTO THE
LOWER MS VALLEY REGION...
..SYNOPSIS...
SHORTWAVE TROUGH NOW ENTERING THE WRN U.S. WILL UNDERCUT UPPER RIDGE
BLOCK THAT EXISTS FROM THE NRN ROCKIES INTO WRN CANADA. THIS FEATURE
WILL CONTINUE EWD THROUGH THE SRN PLAINS BY THURSDAY
NIGHT...REACHING THE MS VALLEY TOWARD THE END OF THIS PERIOD. SOME
DIFFERENCES IN THE MODELS EXIST WITH THE ECMWF BEING FASTER THAN THE
NAM AND GFS. A COLD FRONT DEMARCATING THE LEADING EDGE OF COLD POLAR
AIR SHOULD EXTEND FROM ROUGHLY SERN GA THROUGH THE SERN U.S. THEN
WWD THROUGH CNTRL AND SWRN TX. THE TX PORTION OF THIS BOUNDARY WILL
ADVANCE SEWD AND EXTEND FROM ROUGHLY THE SERN TX COAST NEWD TO A
WEAK LOW OVER NRN MS BY THE END OF THIS PERIOD. COASTAL FRONT WILL
LIFT NWD THROUGH SERN TX AND THE LOWER MS VALLEY REGION.
..ERN TX THROUGH THE LOWER MS VALLEY AREA...
BOUNDARY LAYER OVER THE WRN GULF IS IN THE PROCESS OF MODIFYING WITH
MID 60S DEWPOINTS OFF THE SRN TX COAST. RICHER GULF MOISTURE WILL
BEGIN RETURNING NWWD THROUGH TX WEDNESDAY AS SLY LOW LEVEL FLOW
INCREASES. BY 12Z WEDNESDAY MID TO UPPER 60S DEWPOINTS WILL LIKELY
RESIDE SOUTH OF A FRONTAL BOUNDARY THAT WILL EXTEND FROM THE NRN
GULF INTO COASTAL LA THROUGH SERN TX. WIDESPREAD ELEVATED CONVECTION
SHOULD BE ONGOING WITHIN ZONE OF ISENTROPIC ASCENT NORTH OF THIS
BOUNDARY OVER PARTS OF THE LOWER MS VALLEY. THIS ACTIVITY WILL LIFT
NEWD ALONG DEEPER BAROCLINIC ZONE THROUGH THE SERN STATES DURING THE
DAY. POTENTIAL WILL EXIST FOR THE MOIST WARM SECTOR TO ADVANCE
INLAND...ESPECIALLY AS A SECONDARY LOW LEVEL JET STRENGTHENS
THURSDAY EVENING IN RESPONSE TO HEIGHT FALLS ASSOCIATED WITH EWD
ADVANCING UPPER TROUGH. STEEPER LAPSE RATES ACCOMPANYING THE EML
SHOULD SPREAD EWD THROUGH THE TX WARM SECTOR AND INTO WRN PARTS OF
THE LOWER MS VALLEY BY THURSDAY NIGHT. WHILE THIS WILL CONTRIBUTE TO
DESTABILIZATION...IT MAY ALSO SERVE TO CAP MUCH OF TX WARM SECTOR
AND POSSIBLY THE LOWER MS VALLEY WARM SECTOR TO SURFACE BASED
STORMS. Q-G FORCING ASSOCIATED WITH EWD ADVANCING SHORTWAVE TROUGH
WILL LIKELY RESULT IN AN INCREASE IN THUNDERSTORMS IN TX POST
FRONTAL REGION BY THURSDAY EVENING. HAIL WILL BE THE MAIN SEVERE
THREAT WITH THIS ACTIVITY GIVEN FAVORABLE MID LEVEL LAPSE RATES AND
EFFECTIVE SHEAR SUPPORTIVE OF MID LEVEL ROTATION WITH SOME OF THE
UPDRAFTS.
A MORE SIGNIFICANT SEVERE THREAT INCLUDING POTENTIAL FOR ISOLATED
TORNADOES AND DAMAGING WIND WILL BE POSSIBLE OVER SRN PARTS OF THE
LOWER MS VALLEY WARM SECTOR WHERE SURFACE BASED STORMS WILL BECOME
MORE LIKELY OVERNIGHT AS HEIGHTS FALL AND THE LOW LEVEL JET
STRENGTHENS. THERE IS SOME CONCERN THAT THE QUALITY WARM SECTOR MAY
REMAIN AT LEAST MODESTLY CAPPED...AND MOST STORMS MIGHT DEVELOP
NORTH OF THE COASTAL FRONT AND ON COOL SIDE OF SEWD ADVANCING COLD
FRONT...IN WHICH CASE THE STORMS WILL REMAIN ELEVATED WITH HAIL
BEING THE PRIMARY THREAT. IF IT BECOMES MORE EVIDENT THAT STORMS
WILL BE ABLE TO DEVELOP IN WARM SECTOR AND ROOT IN THE BOUNDARY
LAYER...A SIGNIFICANT AREA MAY BE INTRODUCED IN LATER OUTLOOKS FOR
THIS REGION.
.DIAL.. 02/20/2008
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