Saturday, September 20, 2008

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 200715
SWODY3
SPC AC 200712

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0212 AM CDT SAT SEP 20 2008

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF NEB INTO SRN
ND...

...NORTHERN AND CENTRAL PLAINS...

BROAD UPPER TROUGHING WILL BECOME THE DOMINANT FEATURE ACROSS THE
PACIFIC NW INTO THE NRN PLAINS MONDAY. SEVERAL EMBEDDED SHORTWAVE
TROUGHS...ONE OF PARTICULAR INTEREST...WILL ROTATE ACROSS THIS
REGION BEFORE EJECTING INTO THE PLAINS. BOTH THE GFS AND NAM ARE
SIMILAR IN TIMING OF MID LEVEL WIND SHIFT EAST OF THE MOUNTAINS INTO
THE HIGH PLAINS BY EARLY EVENING. THIS FEATURE IS SIGNIFICANTLY
STRONGER IN THE GFS...AND MORE FOCUSED THAN LEAD SHORTWAVE DURING
THE DAY2 PERIOD. WITH MOISTURE EXPECTED TO HOLD ACROSS THE
PLAINS...50S SFC DEW POINTS WILL BE MORE THAN ADEQUATE FOR
CONVECTIVE DEVELOPMENT AS LARGE SCALE FORCING SPREADS ATOP DEEP
BOUNDARY LAYER FROM NERN CO INTO WRN SD. THUNDERSTORMS SHOULD
READILY DEVELOP ALONG THIS AXIS AHEAD OF COLD FRONT BY LATE
AFTERNOON. FORECAST SHEAR PROFILES STRONGLY SUGGEST DEEP ROTATION
AND GIVEN THE INSTABILITY EXPECTED INITIAL DEVELOPMENT SHOULD BE
SUPERCELLULAR. WITH TIME STORM MERGERS AND LINEAR FORCING COULD
FORCE A SQUALL LINE AS UPPER TROUGH EJECTS INTO SD/NEB DURING THE
OVERNIGHT HOURS.

..DARROW.. 09/20/2008

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