DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 272000
SWODY1
SPC AC 271957

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0157 PM CST THU DEC 27 2007

VALID 272000Z - 281200Z

..NO SVR TSTM AREAS FORECAST...

..EAST TX/LA/SRN AR/MS...
THE LATEST WATER VAPOR IMAGERY SHOWS A HIGHLY MERIDIONAL UPPER-LEVEL
TROUGH OVER THE FOUR CORNERS REGION. AN IMPRESSIVE 110 KT MID-LEVEL
JET IS ROUNDING THE BASE OF THE TROUGH. AT LOW-LEVELS...A 40 TO 45
KT LOW-LEVEL JET IS LOCATED ACROSS WCNTRL TX AND THIS FEATURE WILL
STRENGTHEN...MOVING EWD INTO EAST TX TONIGHT AS THE TROUGH EJECTS
OUT OF THE SWRN STATES. WARM ADVECTION WITH THE LOW-LEVEL JET AND
INCREASING LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-LEVEL TROUGH
WILL LIKELY SUPPORT THUNDERSTORM DEVELOPMENT IN EAST TX AFTER
MIDNIGHT. SEVERAL MODELS SUGGEST THE CONVECTION WILL EXPAND IN
COVERAGE ALONG THE NOSE OF THE LOW-LEVEL JET MOVING NEWD ACROSS LA
INTO NCNTRL MS LATE TONIGHT.

CONCERNING THE SEVERE POTENTIAL...CURRENT SHIP OBSERVATIONAL DATA
SHOW SFC DEWPOINTS IN THE 60S F REMAINING ABOUT 200 STATUTE MILES
SOUTH OF GALVESTON. THIS APPEARS TOO FAR TO REACH SE TX AND SRN LA
TONIGHT BUT SFC DEWPOINTS REACHING THE 50S F SEEMS REASONABLE. THIS
WILL ALLOW ONLY LIMITED INSTABILITY TONIGHT WITH FORECAST SOUNDINGS
SHOWING MOST OF THE INSTABILITY ABOVE 700 MB. AS A RESULT...MOST OF
THE THUNDERSTORMS THAT INITIATE SHOULD BE ELEVATED AND THIS WILL
LIMIT THE SEVERE POTENTIAL SOMEWHAT. INITIALLY THE MARGINAL SEVERE
THREAT SHOULD REMAIN CLOSE TO SE TX AND SW LA WHERE ROTATING STORMS
WILL HAVE ACCESS TO THE GREATEST LOW-LEVEL MOISTURE AND A FEW STORMS
MAY BECOME SFC-BASED. HOWEVER...THE SEVERE WEATHER POTENTIAL WILL
ALSO EXPAND NEWD ACROSS LA INTO NCNTRL MS LATE TONIGHT AS STRONG
ELEVATED THUNDERSTORMS MOVE AHEAD OF THE LOW-LEVEL JET. FORECAST
SOUNDINGS INDICATE STEEP MID-LEVEL LAPSE RATES WHICH WILL SUPPORT A
HAIL THREAT. ALTHOUGH LESS OF A THREAT...ISOLATED WIND DAMAGE MAY
ALSO OCCUR WITH SOME OF THE FASTER MOVING CELLS. THE SEVERE THREAT
SHOULD REMAIN MARGINAL DUE TO WEAK INSTABILITY.

.BROYLES.. 12/27/2007

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