DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 100553
SWODY1
SPC AC 100551

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1151 PM CST SUN DEC 09 2012

VALID 101200Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM E CENTRAL MS THROUGH
CENTRAL AND NRN AL...NWRN GA AND FAR SERN TN...

...PART OF E CENTRAL MS/CENTRAL-NRN AL/NWRN GA/FAR SERN TN...
A SHORTWAVE TROUGH EXPECTED TO BE OVER OK/ERN KS AT 12Z TODAY WILL
DEAMPLIFY AS IT TRACKS NEWD THROUGH THE MID MS/OH VALLEYS...REACHING
THE NERN STATES LATE MON NIGHT. MEANWHILE...THE PARENT LONGWAVE
TROUGH WILL BE MAINTAINED DURING THE DAY 1 PERIOD OVER INTERIOR
NORTH AMERICA AS AN UPSTREAM SHORTWAVE TROUGH...NOW TRACKING SEWD
ALONG THE BC/AB BORDER...DIGS SSEWD ACROSS THE U.S. ROCKIES REACHING
THE SRN HIGH PLAINS BY 12Z TUE. AT THE SURFACE...A COLD
FRONT...INITIALLY EXTENDING FROM THE LOWER GREAT LAKES/UPPER OH
VALLEY SWWD THROUGH CENTRAL KY/MIDDLE TN TO THE LOWER MS VALLEY...IS
FORECAST TO ADVANCE EWD TO THE ATLANTIC COAST INTO NWRN FL BY EARLY
TUE MORNING.

THE STRONGEST HEIGHT FALLS WITH THE DEAMPLIFYING OK/KS TROUGH ARE
EXPECTED TO REMAIN MAINLY ACROSS THE POST-FRONTAL ENVIRONMENT...
THOUGH THERE IS SOME MODEL CONSENSUS FOR STRONG UPWARD VERTICAL
MOTION TO EXTEND SWD INTO THE SLIGHT RISK AREA. GENERALLY WEAK LAPSE
RATES AND LIMITED SURFACE HEATING ALONG AND E OF THE COLD FRONT
SHOULD PRECLUDE THE DEVELOPMENT OF STRONGER INSTABILITY...WITH
MUCAPE EXPECTED TO BE AOB 500 J/KG. FORECAST SOUNDINGS...ESPECIALLY
THE NAM...SUGGEST THIS CAPE WILL EXTEND THROUGH THE MIXED PHASE
LAYER FAVORABLE FOR CHARGE SEPARATION/LIGHTNING. THESE FACTORS
SUGGEST LOW-TOPPED TSTMS WILL BE POSSIBLE FROM THIS MORNING INTO THE
AFTERNOON ALONG THE COLD FRONT...WITH STRONG DEEP LAYER AND LOW
LEVEL SHEAR FAVORING LEWP/BOWING SEGMENTS. 40-50 KT STORM MOTIONS
AND A STRENGTHENING SWLY LLJ /45-55 KT/ WOULD BE FAVORABLE FOR
DAMAGING WIND GUSTS AS THE PRIMARY SEVERE WEATHER THREAT. LOW LEVEL
SPEED SHEAR AND SOME DIRECTIONAL SHEAR SUGGEST A TORNADO THREAT
CANNOT BE RULED OUT.

ANY SEVERE WEATHER THREAT THAT DOES DEVELOP THIS MORNING INTO THE
EARLY AFTERNOON SHOULD DIMINISH BY LATE AFTERNOON AS THE SRN EXTENT
OF STRONGER FORCING FOR ASCENT MOVES AWAY FROM THE MEAGERLY UNSTABLE
WARM SECTOR.

..PETERS/MOSIER.. 12/10/2012

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