SPC AC 130532
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1132 PM CST SAT DEC 12 2009
VALID 141200Z - 151200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
QUASI-ZONAL PROGRESSIVE UPPER PATTERN WILL CONTINUE MONDAY. ANOTHER
IN A SERIES OF IMPULSES IS FORECAST TO EJECT FROM THE MID MS VALLEY
THROUGH THE GREAT LAKES. THIS FEATURE WILL BE CLOSELY FOLLOWED BY A
NRN STREAM SHORTWAVE TROUGH THAT WILL MOVE INTO THE NRN PLAINS AND
UPPER MS VALLEY. A SRN STREAM SHORTWAVE TROUGH IS FORECAST TO MOVE
INTO WRN TX LATE MONDAY NIGHT. WEAK SURFACE LOW IS FORECAST TO
DEVELOP OVER THE MID MS VALLEY AND LIFT NEWD INTO THE GREAT LAKES
REGION IN ASSOCIATION WITH INITIAL IMPULSE. SWRN EXTENSION OF
TRAILING COLD FRONT WILL MOVE SWD THROUGH THE LOWER MS VALLEY AND
ERN TX.
...SERN TX THROUGH THE LOWER MS VALLEY AREA...
PRIMARY LOW LEVEL JET WILL VEER TO WSWLY AND SHIFT NEWD INTO THE TN
AND OH VALLEYS AS LEAD IMPULSE EJECTS TOWARD THE GREAT LAKES.
TENDENCY FOR THE LOW LEVEL JET TO SHIFT NEWD AWAY FROM THE MOIST
WARM SECTOR WITHIN THE LOW AMPLITUDE AND PROGRESSIVE FLOW REGIME
WILL LIMIT THE RETURN OF RICHER MOISTURE TO SRN PORTIONS OF GULF
COASTAL STATES WHERE UPPER 60S F DEWPOINTS WILL BE POSSIBLE...ALONG
WITH LOW 60S F FARTHER INLAND. WEAK LAPSE RATES AND LIKELIHOOD OF
WIDESPREAD LOW CLOUDS SHOULD LIMIT MLCAPE TO GENERALLY AOB 500 J/KG
EXCEPT POSSIBLY ACROSS SERN TX WHERE INSTABILITY AND LAPSE RATES
COULD BE SLIGHTLY GREATER. EJECTING NRN STREAM IMPULSE WILL PROVIDE
THE IMPETUS TO DRIVE A COLD FRONT SWD INTO ERN TX AND THE LOWER MS
VALLEY MONDAY NIGHT WHERE THUNDERSTORMS WILL LIKELY DEVELOP WITHIN
WARM ADVECTION REGIME ALONG AND SOUTH OF THIS BOUNDARY. IT APPEARS
STRONGER LOW-MID LEVEL FLOW AND VERTICAL SHEAR WILL REMAIN NORTH OF
THE MOISTER BOUNDARY LAYER WHICH WILL BE CONFINED TO THE GULF
COASTAL AREAS. CONVECTION DEVELOPING ALONG AND SOUTH OF COLD FRONT
WILL BE EMBEDDED WITHIN MODEST /30-40 KT/ VERTICAL SHEAR. STORMS
INLAND FROM COAST WILL PROBABLY REMAIN SLIGHTLY ELEVATED ABOVE A
STABLE BOUNDARY LAYER. THIS AND THE TENDENCY FOR THE LOW-LEVEL WINDS
TO WEAKEN WITH TIME SHOULD LIMIT OVERALL SEVERE THREAT...AND AT MOST
ONLY LOW SEVERE PROBABILITIES ARE WARRANTED.
..DIAL.. 12/13/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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