SPC AC 240518
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1118 PM CST MON NOV 23 2009
VALID 241200Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A DYNAMIC LARGE-SCALE REGIME WILL PERSIST OVER THE CONUS THROUGH THE
DAY ONE PERIOD. DEEP-LAYER CYCLONE INITIALLY OVER THE MID/LOWER MO
VALLEY WILL GRADUALLY EVOLVE INTO AN OPEN SYSTEM WHILE ACCELERATING
INTO THE GREAT LAKES. IN ITS WAKE...THE NEXT UPSTREAM SHORT WAVE
TROUGH WILL UNDERGO CONSIDERABLE INTENSIFICATION WHILE DIGGING SEWD
FROM ALBERTA INTO THE NRN PLAINS.
AT THE SURFACE...LOW PRESSURE OVER NRN MO WILL DEVELOP NEWD TOWARD
LAKE MI WHILE TRAILING COLD FRONT PUSHES EWD/SEWD THROUGH THE
MID/LOWER MS VALLEY...AND SWD THROUGH S TX INTO THE NWRN GULF OF
MEXICO.
...S TX...
LOW-LEVEL MOISTURE PROFILE SAMPLED BY 24/00Z BRO SOUNDING IS LIKELY
REPRESENTATIVE OF EXPECTED BOUNDARY LAYER CONDITIONS AHEAD OF FRONT
TODAY. THIS MOISTURE COUPLED WITH DAYTIME HEATING SHOULD CONTRIBUTE
TO MLCAPE OF 1000-2000 J/KG AND LITTLE OR NO CAP. THIS WILL SUPPORT
AN INCREASE IN STORM COVERAGE BY AFTERNOON ALONG AND AHEAD OF COLD
FRONT. WEAK VERTICAL SHEAR WILL PRECLUDE ANY SEVERE WEATHER
THREAT.
...CNTRL/SRN FL...
SCATTERED DIURNAL TSTMS ARE EXPECTED WITHIN W-E ORIENTED BAROCLINIC
ZONE WHERE MLCAPE WILL APPROACH 1000-1500 J/KG. FORECAST SOUNDINGS
INDICATE VEERING WINDS WITH HEIGHT BUT ANY HIGHER MOMENTUM FLOW WILL
LIKELY REMAIN ABOVE 7-8 KM AGL. GIVEN THE RATHER WEAK LOW TO
MIDLEVEL WIND FIELD AND POOR LAPSE RATES...THE POTENTIAL FOR SEVERE
STORMS APPEARS LOW.
...MIDWEST...
DYNAMIC FORCING FOR ASCENT/STEEPENING LAPSE RATES ASSOCIATED WITH
LEAD MIDLEVEL SYSTEM WILL CONTINUE TO PROMOTE POCKETS OF WEAK
CONVECTIVE INSTABILITY AND THE POTENTIAL FOR ISOLATED-SCATTERED
ELEVATED TSTMS ALONG SURFACE LOW TRACK.
..MEAD/GRAMS.. 11/24/2009
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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