SPC AC 242000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0200 PM CST WED DEC 24 2008
VALID 242000Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...LOWER MS TO LOWER OH VALLEYS...
EARLY AFTERNOON SURFACE ANALYSES SHOWED A COLD FRONT CONTINUING TO
OVERTAKE THE LEAD COLD FRONT/PRE-FRONTAL BOUNDARY FROM THE LOWER OH
TO LOWER MS VALLEYS. TRENDS IN REGIONAL RADAR IMAGERY SUGGEST THAT
MORE PERSISTENT FORCED CONVECTION/EMBEDDED TSTMS WILL REMAIN ALONG
THE NRN EXTENT OF THE MERGED COLD FRONTS WHERE UPPER LEVEL FORCING
AHEAD OF THE PROGRESSIVE UPPER MS VALLEY TROUGH WILL BE GREATEST.
HOWEVER...THIS FAR NORTH /LOWER OH VALLEY/...VERY WEAK INSTABILITY
WILL PRECLUDE A SEVERE THREAT WITH NRN EXTENT.
ALTHOUGH INSTABILITY IS GREATER FARTHER S AHEAD OF THE SRN EXTENT OF
THE LEAD COLD FRONT DUE TO GREATER LOW LEVEL MOISTURE/SOME SURFACE
HEATING...DIMINISHING LARGE SCALE ASCENT AS UPPER TROUGH MOVES AWAY
FROM THIS AREA WILL RESULT IN AN OVERALL DECREASE IN TSTM POTENTIAL.
IN ADDITION...MID LEVEL WARM AIR ADVECTION WILL TEND TO CREATE A
THERMODYNAMIC PROFILE THAT WILL INHIBIT CHARGE SEPARATION. THIS
TREND APPEARS TO BE UNDERWAY GIVEN RECENT DIMINISHING TREND IN
LIGHTNING PRODUCTION ACROSS THE LOWER MS VALLEY. DESPITE THESE
TRENDS...STRONG EFFECTIVE BULK SHEAR...SURFACE VORTICITY ALONG THE
CONVECTIVELY ACTIVE COLD FRONT AND WEAK INSTABILITY SUGGEST A
NON-ZERO SEVERE THREAT. THEREFORE...THIS OUTLOOK WILL MAINTAIN LOW
SEVERE PROBABILITIES FOR AN ISOLATED STRONG WIND GUST AND/OR BRIEF
TORNADO FROM PORTIONS OF ERN LA TO NWRN AL THROUGH THE AFTERNOON
WITH ERN EXTENT LIMITED BY MINIMAL INSTABILITY PER 18Z BHM SOUNDING.
MEANWHILE...FARTHER SE...REGIONAL RADAR/SATELLITE IMAGERY INDICATED
LOW-TOPPED CONVECTION HAD FORMED ACROSS SERN LA INTO SRN MS/SWRN AL.
THIS CONVECTION APPEARS TO BE DEVELOPING WITHIN REGIME OF MOIST
ISENTROPIC ASCENT IN THE WAKE OF AN APPARENT GRAVITY WAVE FEATURE
CURRENTLY APPROACHING THE GULF COAST. DESPITE WEAK INSTABILITY
ATTRIBUTED TO SOME SURFACE HEATING AND DEWPOINT IN THE 60S...WEAK
MID LEVEL LAPSE RATES/WARM MID LEVEL TEMPERATURES WILL TEND TO LIMIT
UPDRAFTS FROM REACHING TEMPERATURES COLD ENOUGH FOR CHARGE
SEPARATION/LIGHTNING PRODUCTION.
..PETERS.. 12/24/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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