Friday, September 17, 2010

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 170859
SWOD48
SPC AC 170858

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0358 AM CDT FRI SEP 17 2010

VALID 201200Z - 251200Z

...DISCUSSION...
MODELS CONTINUE TO FORECAST THE PROGRESSION OF TWO UPPER TROUGHS --
AND ASSOCIATED SURFACE SYSTEMS -- ACROSS THE U.S. DURING THE MEDIUM
RANGE PERIOD...BUT DIFFER WITH RESPECT TO TIMING OF THE FEATURES
ALOFT -- AND THUS WITH THE EVOLUTION OF THE SURFACE PATTERN.

THE FIRST SYSTEM IS FORECAST TO CROSS THE ROCKIES DAY 4 /MON.
9-20/...REACHING THE PLAINS DURING THE SECOND HALF OF THE PERIOD.
AN ASSOCIATED SURFACE SYSTEM WILL LIKEWISE CROSS THE NRN AND CENTRAL
PLAINS...THOUGH MODELS DIFFER BY ROUGHLY 6-12 HOURS WITH RESPECT TO
FRONTAL PROGRESS. THUS...WHILE SOME POTENTIAL FOR SEVERE WEATHER
SHOULD EVOLVE DAY 4...TEMPORAL/AREAL UNCERTAINTY PRECLUDES THE
ISSUANCE OF A DAY 4 AREA.

THE FRONT SHOULD CONTINUE ACROSS THE PLAINS AND INTO THE MID AND
UPPER MS VALLEY/UPPER GREAT LAKES REGION BY AFTERNOON DAY 5 /TUE.
9-21/...WITH AN AXIS OF CONVECTIVE/LIMITED SEVERE POTENTIAL POSSIBLE
INVOF THE FRONT. THREAT DOES NOT APPEAR SUFFICIENT TO REQUIRE AN
OUTLOOK AREA ATTM...AS IT APPEARS THAT STRONGER FLOW ALOFT/SHEAR
SHOULD REMAIN N OF THE ZONE OF GREATER DESTABILIZATION POTENTIAL.

AS THE INITIAL FRONT SHIFTS EWD INTO/ACROSS THE NORTHEAST DAY 6
/WED. 9-22/...THE NEXT SURFACE SYSTEM SHOULD BEGIN AFFECTING THE
CENTRAL PORTION OF THE COUNTRY. AS THE SYSTEM MOVES ACROSS THE
PLAINS DAY 7...AN INCREASE IN SEVERE POTENTIAL SHOULD OCCUR...BUT
AGAIN...UNCERTAINTY PRECLUDES HIGHLIGHTING A SPECIFIC THREAT AREA
THIS FORECAST..

..GOSS.. 09/17/2010

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