Thursday, September 16, 2010

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 160847
SWOD48
SPC AC 160846

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0346 AM CDT THU SEP 16 2010

VALID 191200Z - 241200Z

...DISCUSSION...
AS A COLD FRONT MOVES OFF THE NERN U.S. COAST EARLY IN THE PERIOD
PER MEDIUM-RANGE GUIDANCE...THE NEXT MAIN FEATURE OF INTEREST WILL
BE THE WRN U.S. UPPER TROUGH -- FORECAST TO SHIFT SLOWLY EWD ACROSS
THE ROCKIES. THIS TROUGH IS PROGGED TO WEAKEN AS IT EJECTS EWD
TOWARD/INTO THE CENTRAL CONUS THROUGH DAY 5 /MON. 9-20/...DUE TO ITS
IMPINGEMENT ON THE PERSISTENT CENTRAL U.S. RIDGE.

THE GFS AND ECMWF DIFFER FAIRLY SUBSTANTIALLY WITH THE TIMING OF
THIS FEATURE AS IT PROGRESSES EWD -- AND THUS DIFFER LIKEWISE WITH
EVOLUTION OF THE SURFACE PATTERN OVER THE CENTRAL CONUS. THUS --
WHILE THE EJECTION OF THIS STORM SYSTEM WILL LIKELY BE ACCOMPANIED
BY SOME DEGREE OF SEVERE POTENTIAL...UNPREDICTABILITY AT THIS POINT
PRECLUDES HIGHLIGHTING A THREAT AREA.

IN THE WAKE OF THIS EJECTING UPPER FEATURE...A SECOND TROUGH IS
PROGGED TO DIG SEWD INTO THE WRN U.S. MEAN TROUGH POSITION.
PROGRESSION OF THIS FEATURE EWD ACROSS THE ROCKIES IS EXPECTED TO
DRIVE SURFACE CYCLOGENESIS DURING THE LATER COUPLE OF DAYS OF THE
PERIOD...BUT AS WITH THE PRIOR TROUGH EJECTION...UNCERTAINTY ABOUNDS
REGARDING THE DETAILS.

..GOSS.. 09/16/2010

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