Wednesday, September 12, 2007

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 120848
SWOD48
SPC AC 120847

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0347 AM CDT WED SEP 12 2007

VALID 151200Z - 201200Z

..DISCUSSION...
LONG-RANGE MODELS SEEM TO BE COMING INTO BETTER AGREEMENT WITH
TIME...WITH THE GFS AND ECMWF NOW MORE SIMILAR IN THEIR HANDLING OF
THE LARGE-SCALE PATTERN OVER THE CONUS. WITH A LARGE SURFACE HIGH
FORECAST TO SHIFT SLOWLY EWD ACROSS THE ERN HALF OF THE U.S. DAYS
4-5 /SAT. SEPT. 15 TO SUN. SEPT. 16/ IN CONJUNCTION WITH RIDGING
ALOFT ACROSS THE CENTRAL CONUS...LITTLE APPRECIABLE SEVERE POTENTIAL
IS EVIDENT.

MODELS FORECAST THE RIDGE BEGINNING TO WEAKEN/SHIFT EWD DAYS
6-7...WITH MORE ACTIVE WSWLY FLOW SPREADING INTO THE PLAINS. THOUGH
THIS -- AND SOME LIKELIHOOD NOW EVIDENT IN THE MODELS FOR GULF
MOISTURE RETURN INTO THE PLAINS -- WOULD SUGGEST A SLOW INCREASE IN
RELATIVE SEVERE THREAT BEGINNING DAY 6...RATHER SIGNIFICANT
DIFFERENCES IN TIMING WITHIN THE LONG-RANGE MODELS RENDERS OUTLINING
A SPECIFIC THREAT AREA -- BOTH SPATIALLY AND TEMPORALLY -- DIFFICULT
AT THIS TIME.

.GOSS.. 09/12/2007

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