SWODY1
SPC AC 201616
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1116 AM CDT SAT SEP 20 2008
VALID 201630Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...GREAT BASIN...
MORNING WATER VAPOR IMAGERY SHOWS THREE SHORTWAVE TROUGHS AFFECTING
THE UNITED STATES TODAY. ALL THREE WILL POSE RISKS OF ISOLATED
THUNDERSTORM ACTIVITY LATER TODAY AND TONIGHT. THE STRONGEST
FEATURE IS MOVING ACROSS THE NORTHERN GREAT BASIN...AND WILL AFFECT
PARTS OF ORE/ID/UT THIS AFTERNOON AND EVENING. A POCKET OF COOL
TEMPERATURES ALOFT...COUPLED WITH UPWARD FORCING ASSOCIATED WITH
EXIT REGION OF APPROACHING UPPER JET WILL AID IN THE POTENTIAL FOR
SCATTERED THUNDERSTORM DEVELOPMENT. FORECAST SOUNDINGS OVER THIS
REGION SUGGEST A RISK OF HAIL AND GUSTY WINDS IN STRONGER CELLS.
OVERALL THREAT DOES NOT APPEAR TO WARRANT A CATEGORICAL RISK OF
SEVERE AT THIS TIME.
...UPPER MIDWEST...
A FAST-MOVING LOW AMPLITUDE SHORTWAVE TROUGH CURRENTLY OVER MANITOBA
WILL TRACK SOUTHEASTWARD INTO MN/WI THIS AFTERNOON. AHEAD OF THIS
FEATURE...A WEAK SURFACE COLD FRONT WILL EXTEND ACROSS SOUTHERN
MN/WI INTO LOWER MI. RELATIVELY STEEP LOW/MID LEVEL LAPSE RATES AND
SUFFICIENT LOW LEVEL MOISTURE WILL YIELD MLCAPE VALUES OF AROUND 500
J/KG BY LATE THIS AFTERNOON ALONG THE FRONT. MESOSCALE MODELS
INDICATE A BRIEF WINDOW OF OPPORTUNITY FOR THUNDERSTORMS BETWEEN
23-02Z. HOWEVER...DESPITE FAVORABLE THERMODYNAMIC
ENVIRONMENT...VERTICAL SHEAR IS VERY WEAK AND SUGGESTS THAT
CONVECTIVE ORGANIZATION WILL BE MINIMAL. NEVERTHELESS...SMALL HAIL
WILL BE POSSIBLE IN STRONGER CELLS.
..HART/JEWELL.. 09/20/2008
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