Tuesday, October 9, 2007

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 090804
SWOD48
SPC AC 090804

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0304 AM CDT TUE OCT 09 2007

VALID 121200Z - 171200Z

..DISCUSSION...

SEVERE THREAT EXPECTED TO INCREASE OVER THE CNTRL AND SRN PLAINS
SATURDAY DAY 5 THROUGH SUNDAY DAY 6.

LARGE UPPER TROUGH OVER THE ERN U.S. AND OFFSHORE FLOW WILL MAINTAIN
STABLE CONDITIONS OVER MUCH OF THE COUNTRY THROUGH FRIDAY DAY 4.
DETERMINISTIC MODELS INCLUDING THE ECMWF AND GFS AS WELL AS THE MREF
ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT ADVANCING A STRONG SHORTWAVE
TROUGH EWD INTO THE SRN AND CNTRL PLAINS LATE DAY 5 INTO DAY 6. LOW
LEVEL MOISTURE RETURN WILL LIKELY BE SOMEWHAT LIMITED BY OFFSHORE
TRAJECTORIES EMANATING FROM CP HIGH PRESSURE OVER THE ERN
STATES...WITH TRAJECTORIES BECOMING MORE FAVORABLE INTO DAY 6 AS
SURFACE RIDGE AXIS SHIFTS EWD. EXPECTED LESS THAN OPTIMAL MOISTURE
RETURN MAY SERVE AS A LIMITING FACTOR. HOWEVER...CURRENT INDICATIONS
ARE THAT AS LEE TROUGH DEVELOPS IN ADVANCE OF SHORTWAVE TROUGH AND
SURFACE RIDGE SHIFTS EAST...AT LEAST PARTIALLY MODIFIED GULF AIR
WILL RETURN NWD BENEATH STEEPENING LAPSE RATES. INSTABILITY MAY
BECOME SUFFICIENT FOR SEVERE STORMS AS VERTICAL WIND PROFILES
STRENGTHEN WITH APPROACHING SHORTWAVE TROUGH.

.DIAL.. 10/09/2007

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