SWOD48
SPC AC 180859
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT WED MAR 18 2009
VALID 211200Z - 261200Z
...DISCUSSION...
MODEL DIFFERENCES CONTINUE THIS PERIOD...PARTICULARLY BEYOND DAY 6
/MON. 3-23/...WITH THE GFS REMAINING MORE PROGRESSIVE WITH THE
EJECTION OF THE WRN U.S. TROUGH.
THE GFS EJECTS THE UPPER TROUGH INTO THE PLAINS DAY 6...AND THEN
INTO THE N CENTRAL CONUS DAY 7. WHILE THE ECMWF ALSO EJECTS A PIECE
OF THE TROUGH INTO THE PLAINS DAY 6...THE LARGER-SCALE TROUGH LAGS
WWD...AS A SECOND/SMALLER-SCALE TROUGH DIGS SEWD ACROSS THE DESERT
SW AS THE INITIAL FEATURE SHIFTS INTO THE PLAINS. THUS -- DUE TO
THESE MODEL DIFFERENCES...CONFIDENCE IN EVOLUTION OF THE SEVERE
THREAT DIMINISHES AFTER DAY 6.
FOR DAY 6 HOWEVER...IT APPEARS THAT A LOW/COLD FRONT WILL CROSS THE
PLAINS AHEAD OF A SUBSTANTIAL/EJECTING UPPER FEATURE. WITH SEVERAL
PRIOR DAYS OF SLY LOW-LEVEL FLOW OFF AN OPEN GULF...THERMODYNAMIC
ENVIRONMENT SHOULD BE SUFFICIENT -- GIVEN ANTICIPATED STRENGTH OF
FLOW ALOFT -- TO SUPPORT THE POTENTIAL FOR A WIDESPREAD SEVERE
WEATHER EPISODE. THUS...WILL INTRODUCE A THREAT AREA DAY 6.
..GOSS.. 03/18/2009
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