DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 140947
SWOD48
SPC AC 140946

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0346 AM CST SAT DEC 14 2013

VALID 171200Z - 221200Z

...DISCUSSION...
CONSENSUS MODEL GUIDANCE INDICATES THE LARGE SCALE FLOW PATTERN WILL
UNDERGO A MAJOR CHANGE BEGINNING ON DAY 5/WED AS A STRONG UPPER
TROUGH DIGS SWD ALONG THE PACIFIC COAST AND CLOSES OFF INTO A LOW
OVER SRN CA BY DAY 6/THU. THIS WILL RESULT IN SWLY FLOW ALOFT
BECOMING ESTABLISHED ACROSS MUCH OF THE CONUS WITH SURFACE PRESSURE
FALLS DEVELOPING OVER THE PLAINS. SUBSEQUENT PATTERN EVOLUTION
BECOMES INCREASINGLY UNCERTAIN...HOWEVER...WITH THE GFS AND ECMWF
DETERMINISTIC RUNS EXHIBITING LITTLE RUN-TO-RUN CONTINUITY OVER THE
PAST 24 HRS WHICH IS ALSO REFLECTED BY THE INCREASING SPREAD IN
THEIR RESPECTIVE ENSEMBLE SYSTEM MEMBERS. MORE RECENT MODEL RUNS
ALSO SHOW FORECASTS OF THE UPPER AIR AND SURFACE SYSTEMS TRENDING
GENERALLY FARTHER WEST WITH TIME AND SUBSTANTIAL VARIABILITY IN THE
PLACEMENT OF SYNOPTIC SCALE FEATURES. ALTHOUGH IT APPEARS THAT GULF
MOISTURE WILL BEGIN RETURNING NWD INTO PARTS OF THE SRN PLAINS/LOWER
MS VALLEY DURING THE DAY 6-8 PERIOD /THU-SAT/ WITH A RESULTANT
INCREASE IN THUNDERSTORM POTENTIAL...LOW PREDICTABILITY IN THE
SYNOPTIC PATTERN EVOLUTION WILL PRECLUDE INTRODUCTION OF A REGIONAL
SEVERE THREAT AREA AT THIS TIME.

..WEISS.. 12/14/2013

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