DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 210539
SWODY1
SPC AC 210537

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1237 AM CDT FRI SEP 21 2012

VALID 211200Z - 221200Z

...NO SVR TSTM AREAS FORECAST...

...MID MS VALLEY...

LATE EVENING MODELS ARE IN GENERAL AGREEMENT REGARDING THE EVOLUTION
OF UPPER TROUGH AS IT DIGS SEWD ACROSS THE UPPER GREAT LAKES INTO
THE OH VALLEY REGION. IN RESPONSE TO THIS FEATURE A WEAK SFC LOW
WILL DEVELOP OVER THE MID MO VALLEY THEN TRACK SEWD TOWARD ECNTRL
MO/WCNTRL IL BY 22/00Z. LOW LEVEL WARM ADVECTION ATOP NWD ADVANCING
WARM FRONT IS EXPECTED TO INDUCE ELEVATED CONVECTION ACROSS SRN MO
THROUGH THE MORNING FRIDAY. WHILE THIS ACTIVITY MAY PRODUCE
MARGINALLY SEVERE HAIL OR PERHAPS EVEN SOME GUSTY WINDS IT APPEARS
THIS ACTIVITY SHOULD REMAIN MOSTLY SUB-SEVERE IN NATURE AS IT
SPREADS/DEVELOPS DOWNSTREAM TOWARD SRN IL. NAM/RUC40 GUIDANCE
SUGGEST MODEST DESTABILIZATION IN THE WAKE OF THIS ELEVATED
CONVECTION BUT IT/S NOT ENTIRELY CLEAR WHETHER WARM SECTOR TSTMS
WILL DEVELOP WITHIN VEERED BOUNDARY LAYER REGIME. EVEN SO THERE IS
SOME CONCERN THAT A NARROW WINDOW OF OPPORTUNITY FOR SFC-BASED
CONVECTION WILL EVOLVE NEAR THE SFC LOW AROUND 00Z ACROSS ECNTRL
MO/WCNTRL IL BUT FORECAST INSTABILITY MAY BE TOO WEAK TO WARRANT ANY
MEANINGFUL THREAT OF SEVERE DESPITE THE INCREASING DEEP LAYER
VERTICAL SHEAR. FOR NOW WILL MAINTAIN LESS THAN 5 PERCENT SEVERE
PROBABILITIES BUT WILL REEVALUATE MOISTURE/INSTABILITY RETURN AS
MORE DATA IS AVAILABLE AFTER SUNRISE.

...FL...

DEEP MOIST PROFILES WILL PERSIST ACROSS THE FL PENINSULA FRIDAY AS
WEAK SWLY FLOW REGIME PERSISTS AHEAD OF DIGGING GREAT LAKES/OH
VALLEY TROUGH. CONVECTION SHOULD READILY DEVELOP AGAIN DURING THE
DAY AS DIURNAL HEATING CONTRIBUTES TO WEAK CONVECTIVE THERMALS THAT
SHOULD PRODUCE SCATTERED TSTMS.

...ELSEWHERE...

SCATTERED CONVECTION WILL DEVELOP BENEATH THE COLD UPPER TROUGH
WITHIN FAVORED REGIONS INFLUENCED BY WARMER LAKE WATERS. WHILE
LIGHTNING SHOULD REMAIN CONCENTRATED OVER THE OPEN WATERS A FEW
STORMS COULD DRIFT INLAND BEFORE WEAKENING.

..DARROW/GARNER.. 09/21/2012

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