SWODY1
SPC AC 250028
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0728 PM CDT MON AUG 24 2009
VALID 250100Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...
...NRN AND CNTRL PLAINS...
A LOW-AMPLITUDE SHORT-WAVE TROUGH IS EVIDENT ON WATER VAPOR IMAGERY
EXTENDING SWWD FROM MANITOBA INTO WRN ND. AT THE SFC...A COLD FRONT
EXISTS FROM NW MN SWWD INTO NRN SD. RUC ANALYSIS SUGGESTS A CAPPING
INVERSION IS CURRENTLY PRESENT ACROSS MOST OF THE REGION BUT
FORECAST SOUNDINGS GRADUALLY QUICKLY COOL THE MID-LEVELS AND WEAKEN
THE CAP ALONG THE BOUNDARY THIS EVENING. THIS COMBINED WITH
INCREASING LARGE-SCALE ASCENT FROM THE APPROACHING SHORT-WAVE TROUGH
SHOULD AID CONVECTIVE DEVELOPMENT LATER THIS EVENING FROM NW MN SWWD
INTO NERN SD. THE ENVIRONMENT AHEAD OF THE COLD FRONT IS
CHARACTERIZED BY UPPER 60S F DEWPOINTS...MODERATE TO STRONG
INSTABILITY AND 35 TO 45 KT OF VERTICAL SHEAR. THIS SHOULD SUPPORT
AN ISOLATED SEVERE THREAT AS STORMS INCREASE IN COVERAGE LATER THIS
EVENING. THE BETTER THREAT FOR HAIL SHOULD EXIST ACROSS SE ND AND NE
SD WHERE INSTABILITY AND MID-LEVEL LAPSE RATES ARE MORE FAVORABLE.
ISOLATED WIND DAMAGE MAY ALSO OCCUR ESPECIALLY IF A LINE-SEGMENT CAN
ORGANIZED ACROSS THE REGION.
FURTHER SOUTHWEST ACROSS CNTRL NEB INTO NW KS AND ERN CO...SCATTERED
THUNDERSTORMS ARE DEVELOPING AHEAD OF A PRONOUNCED SHORTWAVE TROUGH
EVIDENT ON WATERY VAPOR IMAGERY. THE STRONGER STORMS ARE LOCATED
BEHIND THE COLD FRONT IN AN AREA WHERE PRECIPITABLE WATER VALUES ARE
MAXIMIZED ACCORDING TO THE RUC. ALTHOUGH SFC DEWPOINTS AND
INSTABILITY ARE ON THE LOW-SIDE FOR SEVERE STORMS...THE GOODLAND
WSR-88D VWP SHOWS ABOUT 40 KT OF VERTICAL SHEAR. THIS ALONG WITH
STEEP LOW-LEVEL LAPSE RATES MAY BE ENOUGH FOR ISOLATED STRONG WIND
GUSTS. HAIL WILL ALSO BE POSSIBLE WITH THE MORE INTENSE CELLS EARLY
THIS EVENING.
..BROYLES.. 08/25/2009
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