DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 070940
SWOD48
SPC AC 070940

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0340 AM CST SAT DEC 07 2013

VALID 101200Z - 151200Z

...DISCUSSION...
MEDIUM-RANGE MODELS DEPICT A SLOW EWD PROGRESSION OF THE LARGE-SCALE
TROUGH AFFECTING MOST OF THE U.S. AT THE START OF THE PERIOD. WITH
TIME...THE TROUGH IS FORECAST TO ADVANCE ACROSS THE CENTRAL AND ERN
PORTIONS OF THE COUNTRY -- AS MULTIPLE SMALLER-SCALE/EMBEDDED
TROUGHS PROGRESS THROUGH THE BROADER CYCLONIC FLOW FIELD.

SUBTLE DIFFERENCES EXIST ALOFT BETWEEN THE DIFFERENT MODELS -- EVEN
AT THE START OF THE PERIOD WHERE THE GFS FORECASTS WEAK CYCLOGENESIS
EARLY DAY 4 /TUE. 12-10/ OVER THE SC VICINITY...ALONG A BAROCLINIC
ZONE ASSOCIATED WITH AN ADVANCE OF CONTINENTAL POLAR AIR THROUGH THE
SOUTHEAST PORTION OF THE CONUS. MEANWHILE...THE FASTER ECMWF SHOWS
THIS BOUNDARY FARTHER TO THE SOUTHEAST...WITH NO FRONTAL WAVE
DEVELOPMENT GIVEN THE SUBTLY DIFFERENT ORIENTATION OF THE UPPER
TROUGHING.

IN ANY CASE...ANY SEVERE WEATHER RISK WHICH MAY EVOLVE ONSHORE NEAR
THIS FRONT -- AND POSSIBLE FRONTAL WAVE -- WOULD BE QUITE ISOLATED
AT BEST...THUS NOT REQUIRING AREAL DELINEATION.

AFTER DAY 4...AS THE UPPER TROUGH PROGRESSES EWD AND THE SURFACE
FRONT MOVES OFF THE ATLANTIC COAST...ANY SEVERE RISK SHOULD LIKEWISE
VACATE THE CONUS. AS THE THIS TROUGH SHIFTS OFFSHORE AROUND DAY
6...MODEL DIFFERENCES INCREASE WITH RESPECT TO A SRN STREAM TROUGH
PROGGED TO BE SHIFTING INTO THE SWRN/S CENTRAL STATES. THUS
DIMINISHING FORECAST CONFIDENCE WILL EXTEND THROUGH THE END OF THE
PERIOD.

..GOSS.. 12/07/2013

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