SWODY1
SPC AC 121356
DAY 1 CONVECTIVE OUTLOOK RESENT 1
NWS STORM PREDICTION CENTER NORMAN OK
0756 AM CST MON NOV 12 2007
VALID 121300Z - 131200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
A PRONOUNCED NRN STREAM SHORTWAVE TROUGH AND ASSOCIATED SURFACE
CYCLONE OVER ONTARIO WILL PROGRESS ENEWD ACROSS JAMES BAY TO
QUEBEC...WHILE A TRAILING COLD FRONT MOVES SEWD ACROSS THE GREAT
LAKES TO THE OH VALLEY...AND SWD FROM THE CENTRAL INTO THE SRN
PLAINS. THE ONTARIO MID LEVEL TROUGH IS PHASED LOOSELY WITH ANOTHER
WAVE OVER THE WRN DAKOTAS/WY...AND THIS HIGH PLAINS TROUGH WILL
TRANSLATE ESEWD TO THE MID MS VALLEY /IN PROXIMITY TO THE SURFACE
COLD FRONT/ BY LATE IN THE PERIOD. A SEPARATE SRN STREAM TROUGH
OVER TX/OK WILL EJECT EWD TO THE LOWER MS VALLEY AND SRN
APPALACHIANS WHILE WEAKENING GRADUALLY. ELSEWHERE...A STRONG NRN
STREAM TROUGH AND MID-UPPER JET WILL MOVE INLAND OVER THE PAC NW AND
NRN ROCKIES...WHILE THE MID LEVEL TROUGH OFF THE SRN CA COAST DRIFTS
SWD AND EVOLVES INTO A CLOSED/CUTOFF LOW. THE PRIMARY THUNDERSTORM
THREAT AREA WILL BE FOCUSED ALONG THE LOW-LEVEL MOISTURE AXIS FROM
TX/OK NEWD TO THE OH VALLEY...NEAR AND SE OF THE SURFACE COLD FRONT.
..N TX/ERN OK TO THE OH VALLEY THROUGH TONIGHT...
THE THREAT FOR DEEP CONVECTION WILL BE MODULATED TODAY ACROSS ERN
OK/NE TX/AR/MO BY THE REGION OF ASCENT DOWNSTREAM FROM THE TROUGH
MOVING EWD FROM TX/OK. GRADUAL ASCENT/MOISTENING IN THE LOW-MID
LEVELS WILL REMOVE CONVECTIVE INHIBITION WITHIN THE PRE-FRONTAL WARM
SECTOR AND ALLOW THE FORMATION OF A FEW EMBEDDED THUNDERSTORMS. A
FEW THUNDERSTORMS CAN ALSO BE EXPECTED TODAY INTO TONIGHT ALONG AND
IN ADVANCE OF THE COLD FRONT ACROSS THE OH VALLEY. MOISTURE WILL
SPREAD ENEWD NEAR/ABOVE THE GROUND AND CONTRIBUTE TO WEAK
INSTABILITY BASED NEAR 850 MB. WEAK LOW-LEVEL WAA...AS WELL AS
ASCENT ALONG THE FRONT LATER IN THE PERIOD...COULD SUPPORT THE
DEVELOPMENT OF A FEW CLUSTERS/BANDS OF ELEVATED THUNDERSTORMS.
THE 12Z OUN SOUNDING REVEALED MID LEVEL LAPSE RATES NEAR 8 C/KM AND
MUCAPE APPROACHING 1500 J/KG. THIS THERMODYNAMIC PROFILE COULD
SUPPORT STORMS WITH HAIL THE FIRST HALF OF THE DAY. HOWEVER...SHARP
WARMING HAS BEEN OBSERVED IN THE 500-300 MB LAYER FROM 00Z TO 12Z AT
MAF...AND THIS WARMING ALOFT WILL SPREAD NEWD OVER TX/OK AS THE SRN
STREAM WAVE PASSES DURING THE DAY. THEREFORE...DESPITE AFTERNOON
TEMPERATURES IN THE 70S AND DEWPOINTS IN THE LOWER 60S ALONG THE
SURFACE COLD FRONT FROM SW MO INTO CENTRAL OK...MUCAPE COULD
DECREASE SLIGHTLY WITH DAYTIME HEATING. THIS WARMING ALOFT...IN
COMBINATION WITH ALREADY WEAK EFFECTIVE BULK SHEAR...SUGGESTS THAT
THE OVERALL SEVERE STORM THREAT WILL REMAIN QUITE MARGINAL.
.THOMPSON/LEVIT.. 11/12/2007
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