SWODY1
SPC AC 020530
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 AM CDT SUN SEP 02 2007
VALID 021200Z - 031200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
DOMINANT UPPER AIR FEATURE WILL REMAIN RIDGING FROM GREAT
BASIN/4-CORNERS REGION EWD ACROSS CENTRAL PLAINS. WITHIN NWD
EXTENSION OF THAT RIDGING...HEIGHTS ALOFT ARE FCST TO RISE SLIGHTLY
ACROSS NRN PLAINS BEHIND SHORTWAVE TROUGH NOW OVER MB. AS TROUGH
MOVES EWD ACROSS JAMES BAY/FAR NRN ONT AREA TOWARD WRN
QUE...ASSOCIATED COLD FRONT WILL MOVE EWD/SEWD OVER NRN ONT AND LS.
TRAILING PORTION OF THIS FRONT -- NOW OVER CENTRAL/SWRN SD AND ERN
ND -- IS FCST TO SETTLE SEWD TO WI...SRN MN AND SERN SD BEFORE
STALLING...WHILE RETREATING NWD ACROSS WRN SD AND NERN WY/SERN MT AS
WARM FRONT. THIS WILL OCCUR IN CONJUNCTION WITH LEE-SIDE
CYCLOGENESIS OVER ERN MT.
..NRN PLAINS...
STG HEATING AND FAVORABLE MOISTURE FOR CONVECTION IS EXPECTED ALONG
SFC FRONT...FROM UPPER MS VALLEY WWD ACROSS ERN/CENTRAL SD.
VERTICAL SHEAR IS EXPECTED TO INCREASE WITH NWWD EXTENT ALONG WARM
FRONT OVER WRN SD INTO ERN MT...WITH SOME DECREASE IN LOW LEVEL
MOISTURE. HOWEVER...STG CAPPING...WEAK LOW LEVEL FLOW...AND
ASSOCIATED LACK OF CONVERGENCE WILL RENDER DIURNAL CONVECTIVE
POTENTIAL TOO CONDITIONAL/ISOLATED FOR GEN THUNDER FCST ATTM.
INSTEAD....TSTM AREA IS BASED ON POTENTIAL FOR NOCTURNAL DEVELOPMENT
ACROSS PORTIONS ND IN ASSOCIATION WITH LOW LEVEL WAA/MOIST ADVECTION
AND PEAK SLY LLJ OF AROUND 35-45 KT BETWEEN 03/04Z-03/12Z.
EFFECTIVE SHEAR VALUES AOA 50 KT INDICATE SOME POTENTIAL FOR
ORGANIZED TSTMS AND HAIL...HOWEVER SVR PROBABILITIES ARE PRECLUDED
BY CONCERNS OVER COVERAGE/DURATION OF CONVECTION AND MEAGER ELEVATED
CAPE.
..SWRN CONUS...GREAT BASIN....
WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP OVER BROAD SWATH OF
W-CENTRAL/SWRN STATES TODAY AS STG HEATING OF HIGHER TERRAIN...AND
FAVORABLE LOW LEVEL MOISTURE...CONTRIBUTE TO AFTERNOON INITIATION.
HOT SFC AIR MASS WITH ACCOMPANYING DEEPLY-MIXED BOUNDARY LAYERS
AGAIN SHOULD CHARACTERIZE LATE AFTERNOON AIR MASS ACROSS LOWER
ELEVATIONS/DESERTS OF AZ AND SRN CA...AND SOME GUSTS APCHG SVR
LIMITS CANNOT BE RULED OUT. HOWEVER...FCST MID-UPPER LEVEL LAPSE
RATES...AND POTENTIAL FOR POCKETS OF DRYING AT VARIOUS
LEVELS...INDICATE MORE CONDITIONAL/ISOLATED THREAT FOR SUCH EVENTS
THAN PRIOR DAYS.
..SERN CONUS...GULF COASTAL PLAIN...
ANY SVR THREAT SHOULD BE TOO ISOLATED..MRGL AND BRIEF TO WARRANT
PROBABILITIES AOA 5 PERCENT ATTM. BROAD AREA OF TROUGHING ALOFT
WILL CONTINUE ACROSS MOST OF GULF COAST AND ERN ATLANTIC COASTAL
PLAIN...WITH SEVERAL EMBEDDED VORTICITY MAXIMA. BENEATH THIS
TROUGHING...DIURNAL HEATING AND RICH LOW LEVEL MOISTURE AGAIN WILL
SUPPORT WIDELY SCATTERED TO SCATTERED...MAINLY AFTERNOON TSTM
DEVELOPMENT IN MULTICELL CLUSTERS. AS UPPER LOW NOW OVER COAHUILA
MOVES WWD ACROSS NRN MEX...RIGHT ENTRANCE REGION OF 60-70 KT UPPER
JET MAY CONTRIBUTE TO UVM ACROSS PORTIONS S TX AS WELL.
.EDWARDS.. 09/02/2007
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