SWOD48
SPC AC 100859
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT MON SEP 10 2007
VALID 131200Z - 181200Z
..DISCUSSION...
MOST RECENT RUNS OF THE GFS AND ECWMF ARE REMARKABLY SIMILAR THROUGH
DAY 5...AFTER WHICH DIVERGENCE IN THE TWO RUNS INCREASES STEADILY
THROUGH THE END OF THE PERIOD.
BOTH MODELS DEPICT A COLD FRONTAL SURGE ACROSS THE U.S. THROUGH DAYS
4 AND 5. THE FRONT IS FORECAST TO MOVE OFF THE ATLANTIC COAST AND
WELL S INTO THE GULF OF MEXICO -- ACCORDING TO THE GFS -- BY THE END
OF DAY 5 /12Z SAT. SEPT. 15/...AS A LARGE CANADIAN HIGH SETTLES SWD
INTO THE CENTRAL CONUS. BY THIS TIME HOWEVER...MODELS HAVE BEGUN TO
DIVERGE...WITH THE ECMWF MUCH WEAKER AND FURTHER E WITH THE
HIGH...THUS ALLOWING THE FRONT TO LINGER OVER THE SRN CONUS INSTEAD
OF PENETRATING SWD INTO THE GULF. AS A RESULT...THE ECMWF IS MORE
BULLISH WITH THE POTENTIAL FOR THE RETURN OF A HIGHER THETA-E
AIRMASS INTO THE CENTRAL AND SRN PLAINS AHEAD OF THE NEXT SYSTEM --
WHILE THE GFS MAINTAINS A CLOSED GULF AND THUS MUCH LOWER LIKELIHOOD
OF VIGOROUS CONVECTION.
IN THE SHORTER TERM /DAYS 4-5/...MODELS ARE LESS SUGGESTIVE OF A
SEVERE EVENT OVER THE SRN HIGH PLAINS THU. SEPT. 13 -- I.E. DAY
4...WITH THE THREAT NOW APPEARING LESS SIGNIFICANT AND SOMEWAT
FURTHER E INTO KS/OK AS COMPARED TO PRIOR MODEL RUNS. THUS WILL NOT
MAINTAIN AN OUTLOOK AREA DAY 4.
AS THE MAIN COLD FRONT PRESSES FURTHER S DAY 5...WEAK SHEAR IS
EXPECTED S OF THE FRONT WHICH SHOULD LIMIT WARM SECTOR SEVERE
POTENTIAL. A LIMITED THREAT FOR HAIL WITH ELEVATED STORMS COULD
EXIST N OF THE FRONT ACROSS OK WHERE FLOW ALOFT WILL LIKELY BE
SLIGHTLY STRONGER...BUT DEGREE OF THREAT DOES NOT APPEAR TO WARRANT
INCLUSION OF AN OUTLOOK AREA ATTM.
.GOSS.. 09/10/2007
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