SWOD48
SPC AC 210850
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0350 AM CDT TUE SEP 21 2010
VALID 241200Z - 291200Z
...DISCUSSION...
MEDIUM-RANGE MODELS HAVE COME INTO MUCH BETTER AGREEMENT OVER THE
PAST 24 HOURS...WITH THE AGREEMENT REVEALING WHAT APPEARS TO LOW
SEVERE WEATHER PROBABILITY OVERALL THROUGH THE MEDIUM RANGE PERIOD.
THE WEAKENING UPPER TROUGH AND ASSOCIATED SURFACE SYSTEM INITIALLY
AFFECTING THE GREAT LAKES REGION SHOULD PROGRESS EWD ACROSS THE NERN
QUARTER OF THE CONUS DAY 4 /FRI. 9-24/. ONLY LIMITED SEVERE
POTENTIAL APPEARS POSSIBLE ALONG THE TRAILING FRONT -- EXTENDING
FROM THE LOWER LAKES REGION WSWWD ACROSS THE MID MS VALLEY INTO THE
CENTRAL/SRN PLAINS FRIDAY AFTERNOON.
AS THIS SYSTEM VACATES THE CONUS DAY 5 /SAT. 9-25/...THE NEXT SHORT
WAVELENGTH TROUGH IS PROGGED TO DIG SEWD ACROSS THE ERN CONUS INTO
THE LONGER-WAVE MEAN TROUGH POSITION. SOME SEVERE THREAT COULD
OCCUR DAYS 5-7 IN CONJUNCTION WITH POTENTIAL SURFACE CYCLOGENESIS
ALONG THE LINGERING FRONT...AS THE DIGGING UPPER FEATURE EVOLVES
INTO A SLOW-MOVING CLOSED LOW PER LATEST GFS/ECMWF RUNS.
HOWEVER...SOME UNCERTAINTY WITH RESPECT TO THE EVOLUTION THIS SYSTEM
AND LIKELIHOOD THAT STRONGER FLOW ALOFT SHOULD REMAIN DISPLACED TO
THE NW OF THE WARM SECTOR SUGGEST THAT POTENTIAL DOES NOT WARRANT
INCLUSION OF AN OUTLOOK AREA ATTM.
FINALLY...MODELS HINT THAT ANOTHER COLD FRONT COULD MOVE INTO/ACROSS
THE CENTRAL CONUS DAYS 7-8 AS ANOTHER SHORT-WAVE TROUGH MOVES EWD
ACROSS THE CANADIAN PRAIRIE THROUGH FASTER BELT OF MID-LEVEL WLYS
OVER SRN CANADA. HOWEVER...LITTLE INSTABILITY EXPECTED OVER THE
CENTRAL U.S. LATE IN THE PERIOD SUGGESTS LITTLE SEVERE THREAT.
..GOSS.. 09/21/2010
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