SWOD48
SPC AC 170831
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0331 AM CDT TUE MAY 17 2011
VALID 201200Z - 251200Z
...DISCUSSION...
GFS AND ECMWF AGREE THAT UPPER TROUGHING WILL EVENTUALLY SPREAD INTO
THE PLAINS/MS VALLEY...BUT TIMING DIFFERENCES BEGIN TO APPEAR DURING
THE MEDIUM RANGE PERIOD...AS EARLY AS DAY4. GIVEN THE RELUCTANCE OF
THE TROUGH TO ADVECT EWD...AND SHORT RANGE NAM GUIDANCE MORE IN LINE
WITH ECMWF...IT APPEARS THE GFS MAY BE TOO PROGRESSIVE WITH HEIGHT
FALLS ACROSS THE PLAINS INTO THE MID MS VALLEY DAY4. FOR THIS
REASON WILL INTRODUCE A RISK OF ORGANIZED SEVERE THUNDERSTORMS MORE
IN LINE WITH A DELAYED ECMWF. IT/S LIKELY THAT A MARITIME TROPICAL
BOUNDARY LAYER WILL HAVE RETURNED TO THE SRN PLAINS BY LATE WEEK
WITH AT LEAST MODERATE INSTABILITY IN PLACE PRIOR TO LARGE SCALE
FORCING/INTERACTION. IF TIMING OF UPPER TROUGH IS OPTIMIZED WITH
MINIMAL CONVECTIVE INTERFERENCE THEN A SIGNIFICANT SEVERE EVENT MAY
EVOLVE ACROSS THE ERN PLAINS...POSSIBLY EXTENDING INTO PORTIONS OF
THE MS VALLEY BY SATURDAY DEPENDING ON TROUGH PROGRESSION.
..DARROW.. 05/17/2011
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