ZCZC SPCSWODY1 ALL
ACUS01 KWNS 260527
SPC AC 260526

STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK 
DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS.

VALID 261200Z - 271200Z

NO SVR TSTM AREAS FCST.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 70 E BLI 30 ENE PDX
45 SE SLE 65 NNE MFR MFR 30 WSW MFR 10 N OTH.

...WEST OF ROCKIES...
ANTICYCLONIC MID/UPPER FLOW REGIME WILL PERSIST ACROSS THE PACIFIC
COAST STATES THROUGH THIS PERIOD...BUT MODELS INDICATE SIGNIFICANT
DEAMPLIFICATION OF UPPER RIDGE WILL OCCUR AS A FAIRLY STRONG UPPER
TROUGH MIGRATES INLAND ACROSS THE BRITISH COLUMBIA AND PACIFIC
NORTHWEST COAST.  UPPER TROUGH WILL WEAKEN AS WELL...GRADUALLY
BREAKING DOWN INTO SEVERAL SMALLER SCALE SHORT WAVES...BUT COOLING
IN LOWER/MID-LEVELS ALONG/WEST OF THE CASCADES WILL CONTRIBUTE TO
AN INCREASINGLY FAVORABLE THERMODYNAMIC ENVIRONMENT FOR CONVECTIVE
DEVELOPMENT.  MODELS INDICATE SHARP DRYING AT MID-LEVELS WILL OCCUR
ALONG/SOUTH OF 80+ KT 500 MB JET AXIS PROPAGATING ALONG THE BRITISH
COLUMBIA/WASHINGTON BORDER.  THIS WILL ENHANCE CONVECTIVE
INSTABILITY AND ALLOW FOR DAYTIME HEATING OF BOUNDARY LAYER...WHICH
ETA POINT FORECAST SOUNDINGS SUGGEST WILL SUPPORT CAPE OF 250 TO
500 J/KG.  SCATTERED LOW-TOPPED THUNDERSTORMS APPEAR LIKELY...SOME
OF WHICH...PARTICULARLY NEAR PUGET SOUND...MAY PRODUCE SOME SMALL
HAIL IN AN ENVIRONMENT WITH SUFFICIENT VERTICAL SHEAR FOR UPDRAFT
ROTATION. 

...EAST OF ROCKIES...
AN UPPER TROUGH IS CURRENTLY AMPLIFYING ACROSS THE UPPER MIDWEST. 
AMPLIFICATION WILL CONTINUE THROUGH THIS FORECAST PERIOD...WITH
SHARP TROUGH PROGGED THROUGH THE ATLANTIC COAST STATES BY 27/12Z. 
THIS WILL BE ACCOMPANIED BY ANOTHER SURGE OF ARCTIC AIR...WHICH
WILL PROGRESS THROUGH MUCH OF THE CENTRAL/EASTERN U.S. BEFORE A
SUBSTANTIAL RETURN FLOW OF MOISTURE CAN DEVELOP.  

A WEAK MOISTURE RETURN HAS OCCURRED FROM THE WESTERN GULF OF MEXICO
INTO PARTS OF SOUTHEAST TEXAS...SUPPORTING INCREASING DEVELOPMENT
OF SHOWERS IN ZONE OF ENHANCED ISENTROPIC ASCENT ACROSS EASTERN
TEXAS AND LOUISIANA.  MID-LEVEL LAPSE RATES...HOWEVER...ARE NOT
PARTICULARLY STEEP...AND ARE NOT PROGGED TO STEEPEN MUCH FURTHER. 
THIS IS EXPECTED TO MINIMIZE OVERALL THREAT FOR THUNDERSTORMS...BUT
ETA POINT FORECAST SOUNDINGS SUGGEST AN ISOLATED THUNDERSTORM OR
TWO IS POSSIBLE...MAINLY NEAR THE UPPER TEXAS/SOUTHWEST LOUISIANA
COAST DURING THE MORNING HOURS.  AS SOUTHERN PLATEAU/ROCKIES SHORT
WAVE TROUGH DIGS INTO THE MEXICAN PLATEAU...AND UPPER MIDWEST
TROUGH AXIS ROTATES FROM THE GREAT LAKES/MIDDLE MISSISSIPPI VALLEY
INTO THE APPALACHIANS...LARGE-SCALE ASCENT ACROSS SOUTHEAST TEXAS/
LOUISIANA WILL DIMINISH BY THIS AFTERNOON.

..KERR.. 01/26/03

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