SPC AC 280726
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0226 AM CDT THU MAY 28 2009
VALID 301200Z - 311200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LARGE UPPER TROUGH OVER ERN NOAM IS FORECAST TO SHIFT EWD WITH TIME
THIS PERIOD...WHILE ASSOCIATED SURFACE FRONT LINGERS OVER THE FL
VICINITY. MEANWHILE...NW FLOW ALOFT WILL PERSIST ACROSS THE CENTRAL
PART OF THE COUNTRY ON THE BACK SIDE OF THE ERN U.S. TROUGH...WITH A
NW-SE BAROCLINIC ZONE OVER THE CENTRAL U.S. FORECAST TO LINGER --
AND EVENTUALLY SHIFT NWD -- THROUGH THE END OF THE PERIOD.
...SD/NEB ACROSS THE MID AND LOWER MO/MID MS/LOWER OH VALLEYS...
SIMILAR SCENARIO IS FORECAST DAY 3 AS THAT FOR DAY 2...IN THAT
ISOLATED STORMS SHOULD REDEVELOP INVOF THE SURFACE BOUNDARY AND THEN
SHIFT SEWD WITHIN MEAN NWLYS. SEVERAL QUESTIONS LOOM THIS
PERIOD...INCLUDING EXACT POSITION OF THE SURFACE FRONT AND WHETHER
STRONGER FLOW ALOFT REMAINS NEAR THE FRONT...OR MORE TO THE COOL
SIDE OF THE BOUNDARY. THE GFS PLACES THE FRONT ACROSS THE MID AND
LOWER MO VALLEY BY AFTERNOON...WHILE THE NAM DEVELOPS A SECONDARY
W-E BOUNDARY ACROSS KS.
DUE TO THIS UNCERTAINTY...WILL MAINTAIN A LARGE -- BUT AT THIS TIME
LOW PROBABILITY -- THREAT AREA FROM PARTS OF SD/NEB SEWD INTO THE
MID MS AND LOWER OH VALLEYS...TO COVER SEVERE POTENTIAL WITH STORMS
DEVELOPING INVOF THE SURFACE FRONT AND PERHAPS EVOLVING INTO ONE OR
MORE FORWARD/SEWD-PROPAGATING CONVECTIVE CLUSTERS DURING THE
EVENING.
...FL...
SURFACE FRONT LINGERING SOMEWHERE INVOF N FL SUGGESTS THAT A
MOIST/UNSTABLE AIRMASS ACROSS FL WILL SUPPORT THE DEVELOPMENT OF
SHOWERS AND THUNDERSTORMS -- BOTH NEAR THE SURFACE FRONT AND OTHER
LOW-LEVEL/SEA-BREEZE BOUNDARIES. WITH A BELT OF MODEST WLYS ALOFT
FORECAST ACROSS FL...POTENTIAL EXISTS FOR A FEW STRONGER CELLS...AND
THUS WILL INTRODUCE 5% SEVERE PROBABILITY ACROSS MOST OF THE
PENINSULA.
..GOSS.. 05/28/2009
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
|