Saturday, September 1, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 020100
SWODY1
SPC AC 020058

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT SAT SEP 01 2007

VALID 020100Z - 021200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
PROGRESSIVE NRN STREAM PATTERN CONTINUES ALOFT...WHILE STRONG
MID/UPPER RIDGING EXTENDS FROM 4-CORNERS AREA HIGH ENEWD ACROSS
CENTRAL PLAINS AND MID MS VALLEY. SHORTWAVE TROUGH -- NOW EVIDENT
IN MOISTURE CHANNEL IMAGERY OVER ERN/SRN SASK -- IS FCST TO MOVE EWD
ACROSS MB TO EXTREME NWRN ONT BY 02/12Z. FOREGOING/DEEP SFC LOW
WILL REMAIN WELL N OF CANADIAN BORDER...WITH COLD FRONT TRAILING
SWWD ATTM ACROSS NERN ND...WRN SD INTO WRN WY. THIS FRONT WILL MOVE
EWD ACROSS REMAINDER ND...BUT SHOULD WEAKEN AND BECOME
QUASISTATIONARY OVERNIGHT IN CENTRAL/SWRN SD AND ERN WY. PREFRONTAL
TROUGH AND WIND SHIFT LINE IS ANALYZED FROM E-CENTRAL ND SSWWD
ACROSS PIR AREA AND CHERRY COUNTY NEB.

OTHERWISE...DIFFUSE MID/UPPER LEVEL TROUGHING COVERS MUCH OF GULF
COAST AND SRN ATLANTIC COAST...WITH SEVERAL EMBEDDED/MESOSCALE
VORTICITY MAXIMA...IN SUPPORT OF GEN TSTM POTENTIAL OVER THAT
REGION. PRIND THUNDER COVERAGE OVER SERN CONUS AND S TX WILL
DIMINISH GRADUALLY THROUGH REMAINDER PERIOD...WITH SPREADING OUTFLOW
POOLS AND AMBIENT SFC DIABATIC COOLING.

..NRN PLAINS...
ISOLATED TSTMS HAVE DEVELOPED OVER NERN ND JUST S OF BORDER.
ADDITIONAL DEVELOPMENT POSSIBLE NEXT 1-2 HOURS UNTIL CAPPING
STRENGTHENS AGAIN WITH LOSS OF SFC HEATING...AND STRONGEST
ISALLOBARIC FORCING SHIFTS FARTHER AWAY FROM AREA OVER CANADA.
SOMEWHAT MORE SLY SFC WINDS IN AND E OF RED RIVER VALLEY AREA MAY
ENHANCE BOTH LOW LEVEL HODOGRAPHS AND DEEP-LAYER SHEAR...WITH 35-45
KT EFFECTIVE SHEAR VALUES POSSIBLE. ANY SUSTAINED CONVECTION MAY
PRODUCE LARGE HAIL AND DAMAGING GUSTS.

ALTHOUGH SEVERAL BRIEF CB'S HAVE DEVELOPED INVOF PREFRONTAL TROUGH
BETWEEN CENTRAL SD AND NWRN NEB...MODIFIED RUC SOUNDINGS SUGGEST
THAT EXPECTED SFC COOLING WILL INCREASE SBCINH AND REMOVE MLCAPE
OVER NEXT 2-3 HOURS. ANY ADDITIONAL TSTM DEVELOPMENT ALSO SHOULD BE
BRIEF...AND SVR THREAT HAS DIMINISHED BELOW 5 PERCENT MRGL
PROBABILITIES.

STRONG CAPPING SHOULD CONTINUE TO PRECLUDE SFC-BASED CONVECTIVE
DEVELOPMENT ELSEWHERE ALONG FRONTAL ZONE NOW THAT SFC TEMPS HAVE
PEAKED.

..AZ...EXTREME SERN CA...
BKN BAND OF TSTMS HAS FORMED ON HIGHER TERRAIN OF CENTRAL/SERN AZ
AND S-SW OF SRN TIP OF NV...IN CA. THIS ACTIVITY AND ASSOCIATED
OUTFLOW PLUMES WILL MOVE SWWD ACROSS MUCH OF S-CENTRAL/SWRN AZ WITH
POTENTIAL FOR OCCASIONAL STG-SVR GUSTS. ALTHOUGH MID/UPPER LEVELS
OF TUS RAOB APPEAR TO HAVE BEEN ENTRAINED IN CONVECTION AND CONTAIN
SOME BAD DATA...VERY WELL-MIXED/INVERTED-V PROFILE WAS EVIDENT BELOW
CLOUD BASE IN SUPPORT OF CONVECTIVE WIND POTENTIAL.

.EDWARDS.. 09/02/2007

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