SWODY1
SPC AC 151619
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT SAT SEP 15 2007
VALID 151630Z - 161200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
LITTLE CHANGE IS EXPECTED IN THE LARGE SCALE PATTERN OVER THE
CONUS...WITH MID LEVEL TROUGHS PERSISTING OVER THE NERN STATES AND
NEAR THE PAC COAST...AND A MID LEVEL HIGH CENTERED OVER THE SRN
PLAINS. IN THE WAKE OF AN INITIAL STRONG SHORTWAVE TROUGH OVER NEW
ENGLAND...A SURFACE COLD FRONT WILL MOVE EWD OFF THE ATLANTIC
COAST...AND SLOWLY SWD ACROSS N FL AND THE NRN GULF OF MEXICO. THIS
FRONTAL ZONE WILL HELP FOCUS THUNDERSTORM DEVELOPMENT TODAY FROM FL
TO S TX.
WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED THIS AFTERNOON INTO
EARLY TONIGHT WITHIN THE LOW-MID LEVEL MOISTURE PLUME FROM AZ INTO
ERN UT/WRN CO. ALSO...A FEW THUNDERSTORMS WILL BE POSSIBLE FROM THE
HIGH TERRAIN ACROSS NW WY/SW MT/CENTRAL ID WSWWD INTO ORE/EXTREME NW
CA...WHERE STEEP LAPSE RATES AND DAYTIME HEATING COMBINE WITH WEAK
ASCENT AND SUFFICIENT MOISTURE WITHIN THE MID LEVEL DEFORMATION
ZONE.
AN INITIAL CLUSTER OF ELEVATED CONVECTION OVER CENTRAL/SE KS IS
ASSOCIATED WITH WAA AND WEAK INSTABILITY BASED IN THE 850-700 MB
LAYER. THIS CONVECTION MAY PERSIST INTO THE AFTERNOON AS THE BELT
OF WAA SHIFTS EWD...WHILE ADDITIONAL MID LEVEL CONVECTION SHOULD
FORM LATER TODAY/TONIGHT AS FAR E AS MO/IL AS A MID-UPPER SPEED MAX
OVER NW NEB/SW SD CRESTS THE SRN PLAINS HIGH AND MOVES ESEWD TOWARD
MO.
..SE CO AREA LATE THIS AFTERNOON/EVENING...
LEE CYCLOGENESIS IS UNDERWAY ACROSS SE CO...AND BOUNDARY LAYER
DEWPOINTS IN THE MID 50S TO LOWER 60S ACROSS ERN NM AND THE TX
PANHANDLE ARE SPREADING NWD. AFTERNOON TEMPERATURES OF 85-90 F AND
DEWPOINTS OF 56-62 F WILL SUPPORT MLCAPE VALUES OF 1500-2000 J/KG
AND MINIMAL CONVECTIVE INHIBITION IN A SMALL AREA OF SE CO/WRN OK
PANHANDLE/SW KS...WHERE CONVECTIVE INITIATION WILL BE POSSIBLE IN
THE REGION OF LOW-LEVEL MASS CONVERGENCE. IF STORMS FORM...THE
MODERATE INSTABILITY AND DEEP LAYER SHEAR /ON THE SRN FRINGE OF A 60
KT UPPER JET/ COULD SUPPORT A SUPERCELL OR TWO CAPABLE OF PRODUCING
ISOLATED LARGE HAIL AND DAMAGING GUSTS.
..S CENTRAL AZ THIS AFTERNOON...
LOW-LEVEL MOISTURE HAS BEEN INCREASING ACROSS SRN AZ...AND SATELLITE
IMAGERY SHOWS TWO POSSIBLE MCV/S S OF NOGALES. THOUGH THE 12Z
SOUNDINGS FROM PHOENIX AND TUCSON STILL SHOW A PRONOUNCED INVERSION
AROUND 500 MB...THE LOW-LEVEL MOISTENING MAY RESULT IN SUFFICIENT
INSTABILITY FOR THUNDERSTORM DEVELOPMENT INTO SRN AZ THIS AFTERNOON.
THE STRONGEST STORMS COULD PRODUCE GUSTY OUTFLOW WINDS GIVEN THE
TYPICAL INVERTED-V STRUCTURE OF THE AFTERNOON BOUNDARY LAYER.
.THOMPSON/GRAMS.. 09/15/2007
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