Thursday, October 1, 2009

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 010848
SWOD48
SPC AC 010847

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0347 AM CDT THU OCT 01 2009

VALID 041200Z - 091200Z

...DISCUSSION...
SUBSTANTIAL VARIATION IS NOTED IN THE MEDIUM RANGE MODELS THIS
FORECAST...WITH DECENT AGREEMENT BETWEEN THE GFS AND ECMWF ONLY
EVIDENT INTO DAY 5. BOTH MODELS MAINTAIN A NEARLY STATIONARY UPPER
LOW OVER THE GREAT BASIN DAY 4 /SUN. OCT. 4/...WHICH THEN EVOLVES
INTO A LARGE/POSITIVELY TILTED MID-LEVEL TROUGH EXTENDING ACROSS THE
NRN AND WRN CONUS INTO DAY 5.

MODELS THEN BEGIN TO DIFFER IN HANDLING OF THIS TROUGH AND ITS
SMALLER-SCALE COMPONENTS...WHICH HAS SIGNIFICANT INFLUENCE ON THE
DOWNSTREAM CYCLOGENESIS INITIALLY EVOLVING IN LEE OF THE ROCKIES
OVER THE CENTRAL HIGH PLAINS. WHILE SOME SEVERE THREAT APPEARS
POSSIBLE DAYS 4 AND 5 OVER THE CENTRAL CONUS...THREAT DOES NOT
APPEAR SUFFICIENT ATTM TO WARRANT INTRODUCTION OF A THREAT AREA.
FROM LATE DAY 5 ONWARD...MODEL DIFFERENCES BECOME INCREASINGLY
SIGNIFICANT...AND THIS APPARENT LACK OF PREDICTABILITY PRECLUDES THE
INCLUSION OF ANY THREAT AREAS THROUGH THE REST OF THE PERIOD.

..GOSS.. 10/01/2009

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