Thursday, August 30, 2007

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 300900
SWOD48
SPC AC 300859

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT THU AUG 30 2007

VALID 021200Z - 071200Z

..DISCUSSION...
THE LATEST MEDIUM RANGE FORECAST GUIDANCE SUGGESTS THAT THE POLAR
WESTERLIES WILL SHIFT SOUTHWARD INTO THE NORTHERN U.S...AFTER THE
EXTENDED UPCOMING LABOR DAY WEEKEND...INTO THE MIDDLE TO LATTER
PARTS OF NEXT WEEK. THIS IS FORECAST TO OCCUR AS ONE OR MORE
SIGNIFICANT SHORT WAVE IMPULSES...EMANATING FROM A BROAD
NORTHEASTERN PACIFIC TROUGH...CONTRIBUTE TO THE DOWNSTREAM
AMPLIFICATION OF AN UPPER TROUGH ALONG THE CENTRAL CANADIAN/U.S.
BORDER AREA. THIS PROBABLY WILL BE ACCOMPANIED BY WAVE DEVELOPMENT
ALONG A SURFACE FRONTAL ZONE...FROM PARTS OF THE NORTH CENTRAL
PLAINS THROUGH THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES REGION.
HOWEVER...THE SPREAD AMONG GUIDANCE IS LARGE CONCERNING JUST HOW
THIS OCCURS AT THE EXTENDED DAY 7-8 TIME FRAME.

AT THE SAME TIME...IT SEEMS PROBABLE THAT AN INFLUX OF DEEP
LAYER/HIGH MOISTURE CONTENT AIR...AROUND THE WESTERN PERIPHERY OF A
WESTERN ATLANTIC/SOUTHEAST STATES SUBTROPICAL RIDGE...WILL OCCUR.
ASSOCIATED CLOUD COVER/PRECIPITATION COULD COMPLICATE SEVERE
POTENTIAL. BUT...THE RISK FOR AT LEAST HEAVY RAINFALL COULD
INCREASE BY THE END OF THE PERIOD...FROM PORTIONS OF THE SOUTHERN/
CENTRAL PLAINS INTO THE GREAT LAKES REGION.

.KERR.. 08/30/2007

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