DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 220557
SWODY2
SPC AC 220555

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 PM CST WED NOV 21 2012

VALID 231200Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MOST CRUCIAL UPPER-AIR FEATURE FOR THIS FCST WILL BE STG SHORTWAVE
TROUGH NOW CROSSING NRN ROCKIES REGION. THIS PERTURBATION IS FCST
TO MOVE EWD WHILE FURTHER AMPLIFYING...RESULTING IN POSITIVELY
TILTED TROUGH FROM ERN LS SWWD ACROSS PORTIONS NRN/WRN IL AND NRN MO
BY 23/12Z. AS PRIMARY/EMBEDDED VORTICITY CENTER OVER LS EJECTS NEWD
ACROSS NRN ONT...TRAILING 500-MB TROUGH SHOULD SHIFT EWD TO LE...WRN
PA...AND CENTRAL/SRN APPALACHIANS BY 24/00Z. GEN REGIME OF HEIGHT
FALLS WILL CONTINUE OVER E COAST REGION THEREAFTER...AS SERIES OF
LOWER-AMPLITUDE/TRAILING PERTURBATIONS REINFORCES TROUGHING FROM
LOWER GREAT LAKES SWD TO NRN FL.

RELATED SFC COLD FRONT SHOULD BEGIN PERIOD INVOF WRN OH...WRN
TN...SRN AR...AND PORTIONS CENTRAL/SW TX. FRONT SHOULD REACH ERN
NY...NRN VA...WRN SC...AND WRN FL PANHANDLE BY 24/00Z...THEN SWEEP
EWD OFF MOST OF ATLC COAST BY END OF PERIOD.

...SW TX TO SRN AR...
DAY-1 GEN TSTM POTENTIAL OVER NRN PART OF THIS CORRIDOR MAY CARRY
OVER ALONG AND N OF SFC COLD FRONT INTO FIRST FEW HOURS OF THIS
PERIOD...AS ANAFRONTAL LIFT FORCES MRGLLY BUT INCREASINGLY MOIST
EFFECTIVE-INFLOW PARCELS TO LFC. FCST SOUNDINGS AT 23/12Z SHOW WEAK
ELEVATED MUCAPE N OF FRONT -- GENERALLY BELOW 200 J/KG AND ROOTED IN
700-800 MB LAYER -- AS FAR E AS SRN AR...BUT THAT MEAGER BUOYANCY
REACHES INTO THERMAL LAYERS SUITABLE FOR LTG GENERATION. COVERAGE
SHOULD BE ISOLATED TO WIDELY SCATTERED IN THIS REGIME.

LOW-LEVEL MOISTURE RETURN AHEAD OF SFC COLD FRONT WILL BE RATHER
SCANT...GIVEN INCOMPLETENESS OF GULF MARINE-AIR MODIFICATION IN WAKE
OF SYSTEM NOW LOCATED OFFSHORE NRN FL. SFC DEW POINTS 50S F ARE
EXPECTED OVER MOST OF IMMEDIATE PREFRONTAL CORRIDOR IN TX AND AR TO
START PERIOD...TRANSITIONING TO MID-UPPER 60S OVER DEEP S TX PRIOR
TO AFTN FROPA THERE. THOUGH LAPSE RATES ALOFT WILL BE
WEAK...COMBINATION OF THOSE DEW POINTS WITH SFC DIABATIC HEATING MAY
SUFFICE TO REMOVE MLCINH AND YIELD 300-600 J/KG AFTERNOON MLCAPE IN
WARM SECTOR...AVAILABLE FOR CONVECTIVE LIFT ALONG FRONT.
ISOLATED/ELEVATED TSTMS ALSO WILL REMAIN POSSIBLE BEHIND FRONT.
THOUGH BULK OF CONVECTION MAY OCCUR OVER MEX...AT LEAST ISOLATED
TSTM COVERAGE IS POSSIBLE OVER DEEP S TX AND NEAR RIO GRANDE FARTHER
NW. LIMITING FACTORS SHOULD BE RELATIVE WARM LAYER EVIDENT IN SOME
FCST SOUNDINGS JUST ABOVE 700 MB...AS WELL AS LACK OF MORE ROBUST
MOISTURE/INSTABILITY.

..EDWARDS.. 11/22/2012

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