[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 201945
SWODY1
SPC AC 201942

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0142 PM CST WED DEC 20 2006

VALID 202000Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

...E TX TO LOWER MS VALLEY...
COLD FRONT WILL CONTINUE TO SPREAD EWD THIS AFTERNOON THROUGH ERN
OK/TX TOWARD THE MS VALLEY...AND SHOULD EXTEND FROM THE MID MS
VALLEY SWWD THROUGH LA TO OFF THE TX GULF COAST BY 12Z THURSDAY...AS
ASSOCIATED UPPER LOW MOVES SLOWLY TOWARD THE CENTRAL/SRN PLAINS. 
DESPITE MOISTURE ADVECTION INTO THE LOWER MS VALLEY THIS FORECAST
PERIOD...WEAK LAPSE RATES ARE EXPECTED TO MAINTAIN MARGINAL
INSTABILITY...AT BEST...FOR TSTM DEVELOPMENT ALONG AND AHEAD OF THE
COLD FRONT.  ALTHOUGH INSTABILITY IS GREATER SWD ALONG THE TX
COASTAL PLAIN...THE LACK OF STRONGER LARGE SCALE FORCING SHOULD
CONTINUE TO LIMIT THE POTENTIAL FOR DEEP CONVECTION IN THAT REGION.

A WEAK SRN STREAM IMPULSE MOVING NEWD ACROSS THE LOWER MS VALLEY AT
THIS TIME IS LIKELY AIDING IN THE RECENT INCREASE IN TSTM ACTIVITY
JUST OFF THE LA COAST.  THIS ACTIVITY IS LOCATED GENERALLY ALONG AND
NORTH OF A SURFACE BOUNDARY WHICH EXTENDED FROM THE UPPER TX COAST
EWD INTO THE FAR NRN GULF OF MEXICO.  SHORT TERM MODELS SUGGEST THE
WRN EXTENT OF THIS BOUNDARY MAY MOVE INLAND ACROSS FAR SE TX AND SW
LA...THUS INCREASING THE POTENTIAL FOR SURFACE BASED STORMS LATER
TONIGHT.  EFFECTIVE BULK SHEAR AND LOW LEVEL SHEAR VALUES WILL BE
SUFFICIENT FOR ROTATING TSTMS WITH AN ISOLATED TORNADO THREAT. 
HOWEVER...WITH ONLY WEAK INSTABILITY AND THE LACK OF STRONGER
FORCING ALOFT LATER IN THE FORECAST PERIOD...WILL MAINTAIN LOW
SEVERE PROBABILITIES WITH THIS OUTLOOK.

...WRN WA...
PACIFIC TROUGH...CURRENTLY LOCATED NEAR 44 N 134 W...WILL APPROACH
NW WA AND BRITISH COLUMBIA LATE IN THE FORECAST PERIOD.  COLD MID
LEVEL TEMPERATURES WITH THIS SYSTEM AND INCREASING ASCENT SHOULD
MAINTAIN AREA OF TSTMS WITH TROUGH...BUT ANY TSTM THREAT SHOULD
REMAIN OFFSHORE THROUGH 12Z THURSDAY.

..PETERS.. 12/20/2006