DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 101232
SWODY1
SPC AC 101230

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0730 AM CDT MON SEP 10 2012

VALID 101300Z - 111200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
INCREASING WLY FLOW ALOFT /50 TO 70 KT AT 500 MB/ WILL MOVE INTO THE
PACIFIC NW...NRN ROCKIES...AND NRN PLAINS AS A STRONG UPPER LEVEL
TROUGH ROTATES NEWD ACROSS WRN CANADA. JUST AHEAD OF THE THIS
STRONGER FLOW...A WEAKENING SHORTWAVE TROUGH WILL MOVE NEWD FROM SRN
SK INTO WRN ONTARIO WHILE AN ASSOCIATED COLD FRONT MOVES ACROSS MT
AND INTO THE CNTRL DAKOTAS. A STRONG PRESSURE GRADIENT WILL EXIST
BETWEEN THIS COLD FRONT AND A LARGE SFC HIGH OVER MUCH OF THE ERN
CONUS. ELSEWHERE...A LARGE UPPER LEVEL TROUGH WILL CONTINUE EWD OFF
THE ATLANTIC COAST AND A SLOW MOVING UPPER LOW WILL REMAIN OVER SRN
CA AND AZ.

...SOUTHWEST...
AN UPPER LEVEL LOW HAS REMAINED QUASI-STATIONARY OVER THE NRN BAJA
PENINSULA DURING THE PAST FEW DAYS. THIS LOW IS EXPECTED TO
GRADUALLY DRIFT NEWD AS IT BECOME EMBEDDED IN MORE SWLY FLOW. A
MOIST AIR MASS REMAINS OVER THE REGION /CHARACTERIZED BY PW AROUND
1.50 TO 1.75 INCHES/...WHICH SHOULD PROMOTE SCATTERED TSTM
DEVELOPMENT AS IT INTERACTS WITH THE LIFT PROVIDED BY THE UPPER LOW.
SHEAR AND INSTABILITY ARE EXPECTED TO BE MARGINAL AT BEST BUT THE
MOIST ENVIRONMENT WILL SUPPORT POTENTIAL PRECIPITATION LOADING WITH
STRONGER UPDRAFTS. ANY BOUNDARY LAYER MIXING WOULD ALSO INCREASE
STRONG/SEVERE DOWNDRAFT POTENTIAL BUT MOST MODEL GUIDANCE INDICATES
CONVECTION BEGINNING EARLY...LIMITING POTENTIAL MIXING AND
DESTABILIZATION.

...FL...
A COLD FRONT CURRENTLY LOCATED ACROSS CNTRL FL WILL SLOWLY PROGRESS
SWD...SUPPORTING SCATTERED TSTM DEVELOPMENT ACROSS CNTRL/SRN FL.
WEAK FLOW ALOFT AND MARGINAL INSTABILITY ARE EXPECTED TO KEEP THE
SEVERE THREAT BELOW 5 PERCENT. HOWEVER...THE MOIST AIR MASS AS WELL
AS BRIEF UPDRAFT STRENGTHENING DUE TO BOUNDARY INTERACTIONS AND CELL
MERGERS COULD RESULT IN A FEW STRONG UPDRAFTS CAPABLE OF MODEST
PRECIPITATION LOADING AND GUSTY DOWNBURST WINDS.

...SRN PORTIONS OF THE NRN HIGH PLAINS...
INCREASING WLY FLOW AND MODEST HEIGHT FALLS ASSOCIATED WITH THE WRN
CANADA TROUGH MAY RESULT IN ISOLATED TSTMS THIS AFTERNOON AND
EVENING. GIVEN THE DEEP BOUNDARY LAYER MIXING AND INCREASING FLOW
ALOFT...THERE IS A LOW POTENTIAL FOR A FEW STRONG WIND GUSTS.
HOWEVER...THE WEAK INSTABILITY AND MEAGER LOW-LEVEL MOISTURE WILL
KEEP THIS THREAT ISOLATED AT BEST AND THE SEVERE POTENTIAL IS LESS
THAN 5 PERCENT.

..MOSIER.. 09/10/2012

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