SWODY1
SPC AC 051941
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0241 PM CDT WED SEP 05 2007
VALID 052000Z - 061200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF UT...ERN ID AND
WRN WY...
..UT/WRN WY/ERN ID...
LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL LOW CENTERED OVER SW
ID. STRONG LARGE-SCALE ASCENT ALONG THE LEADING EDGE OF A DRY SLOT
ASSOCIATED WITH TROUGH IS SUPPORTING THE DEVELOPMENT OF NUMEROUS
THUNDERSTORMS ACROSS THE REGION. THE LATEST OBJECTIVE ANALYSIS SHOWS
SBCAPE VALUES ABOVE 1000 J/KG ACROSS MUCH OF THE SLIGHT RISK AREA
AND DESTABILIZATION SHOULD CONTINUE LATE THIS AFTERNOON. AS A
RESULT...STORM COVERAGE SHOULD GRADUALLY EXPAND WITH THE CONVECTION
SPREADING NEWD INTO NW CO AND SWRN WY BY EARLY EVENING.
A WELL-DEFINED 60 TO 70 KT MID-LEVEL JET IS CURRENTLY ANALYZED FROM
SRN NV EXTENDING NEWD INTO FAR SW WY. THIS FEATURE IS CREATING
STRONG VERTICAL SHEAR PROFILES ACROSS THE REGION WHICH WILL SUPPORT
SCATTERED SEVERE STORMS. THE SALT LAKE CITY WSR-88D VWP CURRENTLY
SHOWS VERY STRONG SPEED SHEAR IN THE MID-LEVELS WITH ABOUT 70 KT AT
6 KM. THIS APPEARS REPRESENTATIVE OF THE REGIONAL SHEAR ENVIRONMENT
SUGGESTING SOME ROTATING STORMS WILL BE LIKELY. RELATIVELY FAST
STORM MOVEMENT OF ABOUT 35 KT AND STEEPENING LOW-LEVEL LAPSE RATES
SHOULD BE FAVORABLE FOR WIND DAMAGE WITH THE STRONGER CELLS. IN
ADDITION...STEEP MID-LEVEL LAPSE RATES AND COLD AIR ALOFT WITH THE
UPPER-LEVEL LOW WILL SUPPORT A THREAT FOR LARGE HAIL.
FURTHER SOUTH ACROSS CNTRL AND NRN AZ...THE LATEST OBJECTIVE
ANALYSIS SHOWS AN AXIS OF INSTABILITY IN PLACE WITH SBCAPE VALUES
GENERALLY FROM 500 TO 1000 J/KG. AS INSTABILITY INCREASES LATE THIS
AFTERNOON...ISOLATED THUNDERSTORMS SHOULD INITIATE ALONG THE
INSTABILITY AXIS. VERTICAL SHEAR SHOWN ON FORECAST SOUNDINGS WILL BE
MARGINAL FOR SEVERE STORMS. HOWEVER...THE STEEP LOW-LEVEL LAPSE
RATES MAY BE ENOUGH FOR A FEW MARGINALLY SEVERE WIND GUSTS LATE THIS
AFTERNOON. WARMER MID-LEVEL TEMPS SHOULD MAKE THE THREAT FOR HAIL
MINIMAL.
..EAST TX AND THE LOWER MS VALLEY...
LATEST WATER VAPOR IMAGERY SHOWS A WELL-DEFINED UPPER-LEVEL TROUGH
OVER EAST TX. SCATTERED TO NUMEROUS THUNDERSTORMS ARE ONGOING ACROSS
THE REGION AHEAD OF A PRONOUNCED DRY SLOT DUE TO SFC HEATING AND
LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-LEVEL TROUGH. MODERATE
INSTABILITY IS ALREADY IN PLACE PARTIALLY DUE TO SFC DEWPOINTS IN
THE LOWER TO MID 70S F. IN ADDITION...RUC ANALYSIS SHOWS MODERATE
VERTICAL SHEAR PRESENT AT THE BASE OF THE UPPER-LEVEL TROUGH FROM
EAST TX TO ERN AR. THIS COMBINED WITH STEEPENING LOW-LEVEL LAPSE
RATES AND STRONG LOW-LEVEL SHEAR SHOULD SUPPORT A MARGINAL THREAT
FOR WIND DAMAGE OR A BRIEF TORNADO THREAT WITH THE MORE ORGANIZED
STORMS LATE THIS AFTERNOON.
..NRN MN/FAR ERN SD..
LATEST SFC ANALYSIS SHOWS A COLD FRONT LOCATED FROM ERN ND EXTENDING
NEWD INTO FAR NW MN. AS LOW-LEVEL CONVERGENCE INCREASES ALONG THE
BOUNDARY...QUASI-LINEAR CONVECTION SHOULD INITIATE LATE THIS
AFTERNOON. OBJECTIVE ANALYSIS CURRENTLY SHOWS MODERATE INSTABILITY
LOCATED TO THE SOUTHEAST OF THE BOUNDARY WITH STEEP MID-LEVEL LAPSE
RATES IN PLACE ALONG THE BOUNDARY. THIS MAY SUPPORT A MARGINAL HAIL
THREAT LATE THIS AFTERNOON. HOWEVER...THE STRONGER VERTICAL SHEAR IS
LOCATED NORTH OF THE CANADIAN BORDER AND THIS SHOULD LIMIT SEVERE
REPORT COVERAGE.
.BROYLES.. 09/05/2007
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