SWODY2
SPC AC 271731
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CST THU DEC 27 2007
VALID 281200Z - 291200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS SE LA...SRN AND ERN
MS...AL...NW GA...ERN TN AND FAR WRN NC......
..LOWER MS AND TN VALLEYS/SRN APPALACHIANS...
A HIGHLY MERIDIONAL UPPER-LEVEL TROUGH OVER THE WRN U.S. WILL BECOME
NEGATIVELY TILTED TONIGHT AND MOVE QUICKLY NEWD ACROSS THE SRN
PLAINS INTO THE OZARK REGION DURING THE DAY ON FRIDAY. IN
RESPONSE...A 50 KT LOW-LEVEL JET WILL STRENGTHEN ACROSS EAST TX
TONIGHT DEVELOPING EWD INTO THE LOWER MS VALLEY CAUSING RAPID
MOISTURE ADVECTION ON FRIDAY. SFC DEWPOINTS SHOULD INCREASE INTO THE
60S F ACROSS THE SRN HALF OF MS AND ACROSS MOST OF AL AS A COLD
FRONT ADVANCES EWD INTO THE LOWER MS VALLEY AROUND MIDDAY. STRONG
LOW-LEVEL CONVERGENCE SHOULD BE PRESENT JUST AHEAD OF THE COLD FRONT
AND THIS ALONG WITH STRONG WARM ADVECTION SHOULD SUPPORT A LINE OF
THUNDERSTORMS ONGOING AT THE BEGINNING OF THE PERIOD. THE LINE OF
STORMS SHOULD GRADUALLY INTENSIFY BY FRIDAY AFTERNOON AS SFC TEMPS
WARM AND INSTABILITY INCREASES ACROSS THE WARM SECTOR.
CONCERNING THE SEVERE POTENTIAL WITH THE LINE OF THUNDERSTORMS...THE
NAM AND GFS SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT SHOWING STRONG
SPEED SHEAR AND ADEQUATE DIRECTIONAL SHEAR IN THE BOUNDARY LAYER FOR
ROTATING STORMS. THE MODELS ALSO FORECAST 60 F SFC DEWPOINTS ACROSS
A WIDESPREAD AREA AHEAD OF THE LINE. ALTHOUGH MLCAPE VALUES SHOULD
REMAIN BELOW 1000 J/KG EXCEPT ALONG THE IMMEDIATE COASTS OF MS AND
AL...SMALL SFC TEMP-DEWPOINT SPREAD SHOULD RESULT IN LOW LCL HEIGHTS
AND THIS COMBINED WITH THE STRONG LOW-LEVEL SHEAR MAY BE ENOUGH FOR
A TORNADO OR TWO WITH THE MORE PERSISTENT SUPERCELLS EMBEDDED IN THE
LINE. WIND DAMAGE MAY ALSO OCCUR WITH SUPERCELLS AND BOW ECHOES AS
THE SQUALL-LINE REACHES PEAK STRENGTH IN THE AFTERNOON WHEN THE
STORMS ARE MOST LIKELY TO BE SFC-BASED. THERE SHOULD ALSO BE A
SEVERE POTENTIAL WITH ISOLATED SUPERCELLS THAT DEVELOP AHEAD OF THE
LINE IN THE WARM SECTOR. THE WIND DAMAGE POTENTIAL WILL LIKELY
DEPEND ON THE FORWARD SPEED OF THE LINE AND THE AMOUNT OF
DESTABILIZATION THAT TAKES PLACE. ANOTHER FACTOR THAT COULD BECOME
PROBLEMATIC IS THE SPEED OF THE UPPER-LEVEL SYSTEM. MODEL FORECASTS
QUICKLY TAKE THE LOW-LEVEL JET NEWD INTO THE CNTRL APPALACHIAN MTNS
BY LATE AFTERNOON AND THIS COMBINED WITH DECREASING LARGE-SCALE
ASCENT AS THE UPPER-LEVEL SYSTEM PULLS AWAY FROM THE AREA SHOULD
RESULT IN A QUICK DECREASE IN STORM INTENSITY SOMETIME LATE FRIDAY
AFTERNOON.
.BROYLES.. 12/27/2007
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