SWOD48
SPC AC 260844
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0344 AM CDT SAT MAR 26 2011
VALID 291200Z - 031200Z
...DISCUSSION...
THE LARGE SCALE PATTERN WILL REMAIN CHARACTERIZED BY PROGRESSIVE
QUASI-ZONAL FLOW ACROSS THE SRN TWO THIRDS OF THE COUNTRY THROUGH AT
LEAST DAY 5. HOWEVER...SIGNIFICANT MODEL DIFFERENCES AND RUN TO RUN
DISCREPANCIES EXIST REGARDING AMPLITUDE AND TIMING OF WAVES WHICH
LOWERS OVERALL PREDICTABILITY IN THE EXTENDED RANGE.
DAY 4...MODEL CONSENSUS IS THAT A SHORTWAVE TROUGH WILL MOVE FROM
THE CNTRL PLAINS INTO THE OH VALLEY. WEAK CYCLOGENESIS IS FORECAST
BY ECMWF WITH THE SURFACE LOW MOVING FROM THE SRN PLAINS INTO THE TN
VALLEY BY THE END OF THE PERIOD...WHILE COLD FRONT SWEEPS SEWD
THROUGH TX AND THE LOWER MS VALLEY. THE GFS IS MUCH STRONGER WITH
ITS SURFACE LOW DEVELOPMENT...BUT GIVEN LIKELIHOOD THAT STRONGER
FORCING ASSOCIATED WITH THE PROGRESSIVE WAVE WILL REMAIN IN COOL
SECTOR...LOW LEVEL RESPONSE WILL PROBABLY BE WEAKER SUPPORTING THE
ECMWF SOLUTION. IN EITHER CASE...SOME THREAT FOR SEVERE WEATHER WILL
EXIST IN WARM SECTOR FROM ERN TX INTO THE LOWER MS VALLEY WHERE A
MODERATELY UNSTABLE WARM SECTOR WILL RESIDE AND SHEAR WILL BE
SUPPORTIVE OF ORGANIZED STORMS ALONG AND AHEAD OF SEWD MOVING COLD
FRONT. PORTIONS OF ERN TX INTO THE LOWER MS VALLEY MAY NEED TO BE
INCLUDED IN A RISK AREA IN LATER OUTLOOKS.
DAY 6-7...ENSEMBLE SPREADS AND MODEL DIFFERENCES BECOME LARGE WITH
REGARD TO UPPER TROUGH FORECAST TO AMPLIFY OVER THE SERN STATES. GFS
IS SLOWER AND MORE AMPLIFIED...DEVELOPING A DEEPER SURFACE LOW OVER
THE NERN GULF COASTAL REGION...WHILE THE ECMWF HAS TRENDED TO A LESS
AMPLIFIED...WEAKER SOLUTION. SOME THREAT FOR SEVERE WEATHER COULD
EVOLVE ACROSS FL DAY 6...BUT PREDICTABILITY IS TOO LOW AT THIS TIME
GIVEN THE DISPERSIVE MODEL SOLUTIONS.
..DIAL.. 03/26/2011
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