SWODY1
SPC AC 190054
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 PM CDT WED MAR 18 2009
VALID 190100Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
IN MID-UPPER LEVELS...GENERALLY ZONAL TO WNW FLOW PATTERN ACROSS
ROUGHLY SRN 1/3 OF CONUS TRANSITIONS TO BROADLY CYCLONIC REGIME OVER
GREAT LAKES AND UPPER MIDWEST...ASSOCIATED WITH LARGE CYCLONE OVER
NWRN QUE. EMBEDDED/POSITIVELY-TILTED SHORTWAVE TROUGH IS EVIDENT IN
MOISTURE CHANNEL IMAGERY AND AVAILABLE RAOB DATA FROM WRN QUE WSWWD
ACROSS LS AND NRN WI. SRN PORTION OF THIS PERTURBATION SHOULD PIVOT
SEWD OVER WI...LOWER MI AND LM THROUGH REMAINDER PERIOD.
AT 23Z...SFC ANALYSIS SHOWED ASSOCIATED WAVY COLD FRONT FROM SWRN PA
WSWWD OVER SRN PORTIONS INDIANA/IL/MO...BISECTING MAIN BODY OF OK
DIAGONALLY THEN ARCHING SWWD/WWD/NWWD OVER TX SOUTH-PLAINS REGION
AND SERN NM. THIS FRONT IS FCST TO CONTINUE MOVING SLOWLY SWD/SEWD
THROUGH THOSE REGIONS THROUGH REMAINDER PERIOD...REACHING TO NEAR
PHL...ROA...BNA...ELD...DFW...MAF...ELP LINE BY 12Z...WITH WEAK
FRONTAL-WAVE LOWS POSSIBLY DEVELOPING OVER NJ AND NEAR DFW BY THAT
TIME.
...NERN OK TO LOWER GREAT LAKES AND OH VALLEY REGION...
WIDELY SCATTERED TSTMS HAVE BEEN EVIDENT PAST FEW HOURS FROM SRN
INDIANA TO W-CENTRAL MO...MANY OF WHICH ARE N OF SFC COLD FRONT IN
AREA OF ELEVATED FRONTAL LIFT AND LOW LEVEL WAA ABOVE FRONTAL
SURFACE. VIS IMAGERY AND REFLECTIVITY LOOPS ALSO SHOW AREA OF DEEP
CONVECTION -- HIGH BASED GIVEN MODIFIED RAOBS...RUC SOUNDINGS AND
VISUAL APPEARANCE -- FROM TUL AREA SWWD ACROSS PORTIONS CENTRAL OK.
ISOLATED TO WIDELY SCATTERED TSTMS MAY DEVELOP IN BRIEF TIME
WINDOW...THROUGH ABOUT 03Z...BEFORE THEIR SOURCE OF BUOYANCY IS
REMOVED.
GIVEN DRYNESS OF PRE-FRONTAL AIR MASS...AND RELATED DEPENDENCE OF
ITS BUOYANCY ON DIABATIC SFC HEATING AS EVIDENT IN 00Z RAOBS AND RUC
SOUNDINGS...ONLY SLGT SFC COOLING IS NEEDED OVER MOST OF THIS
CORRIDOR TO ELIMINATE SBCAPE. THEREFORE THUNDER
PROBABILITIES/COVERAGE EACH SHOULD DIMINISH THROUGH REMAINDER
EVENING...EXCEPT OVER PORTIONS LOWER OH VALLEY WHERE ISENTROPIC
ASCENT/WAA ABOVE SFC...AND ACCOMPANYING NARROW PLUME OF MRGL
MOISTURE...MAY MAINTAIN ELEVATED MUCAPES UP TO AROUND 200-300 J/KG.
..EDWARDS.. 03/19/2009
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