[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 121718
SWODY2
SPC AC 121717

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1217 PM CDT WED APR 12 2006

VALID 131200Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY INTO
THE GREAT LAKES......

...SYNOPSIS...
BROAD UPPER RIDGE SLOWLY BUILDING OVER THE ROCKIES IS FORECAST TO
PROGRESS EWD ACROSS THE PLAINS...AS DOWNSTREAM UPPER TROUGH
CURRENTLY OVER THE GREAT LAKES MOVES INTO THE NERN STATES TONIGHT. 
WEAK SHORT WAVE TROUGH CURRENTLY OVER BRITISH COLUMBIA IS EXPECTED
TO MOVE ESEWD AS A LOW AMPLITUDE SYSTEM ACROSS THE NRN PARTS OF THE
ROCKIES AND PLAINS...WITH WNWLY UPPER FLOW DEVELOPING ACROSS THE
UPPER MS VALLEY TOMORROW NIGHT.

AT THE SURFACE...LOW PRESSURE OVER NRN/CENTRAL PLAINS WILL GRADUALLY
SPREAD EWD TOWARD THE UPPER MS VALLEY...AS A WARM FRONT ACROSS THE
OH VALLEY WWD INTO KS AT THE START OF THE PERIOD LIFTS NWD INTO THE
UPPER MS VALLEY/SRN GREAT LAKES BY EVENING.  THE LOW IS EXPECTED TO
CONTINUE EWD INTO THE GREAT LAKES REGION OVERNIGHT.

...UPPER MS VALLEY INTO GREAT LAKES...
LOW LEVEL MOISTURE IS EXPECTED TO SPREAD RAPIDLY NWD TOWARD THE
UPPER MS VALLEY DURING THE DAY AS WARM FRONT LIFTS NWD INTO THE
REGION...WITH SURFACE DEW POINTS OF 55-60F MOVING INTO PARTS OF SERN
MN/WRN WI BY 00Z.  STEEPER MID LEVEL LAPSE RATES OF 7.0-7.5 C/KM ARE
FORECAST TO SPREAD EWD ACROSS THE MIDDLE AND UPPER MS VALLEY TOWARD
THE WRN GREAT LAKES IN ASSOCIATION WITH STRONG WESTERLY MID LEVEL
WINDS FROM THE NRN ROCKIES INTO THE GREAT LAKES.  AIR MASS WILL
DESTABILIZE NWD AS LOW LEVEL MOISTURE SPREADS NWD BENEATH THE
STEEPER LAPSE RATES...WITH ELEVATED CAPE OF 1000-1500 J/KG
DEVELOPING NORTH OF THE WARM FRONT AND MLCAPE OF 2000-2500 J/KG WITH
WARM SECTOR.

PRIMARY CONVECTIVE DEVELOPMENT IS EXPECTED TO BEGIN DURING THE LATE
AFTERNOON OR EVENING OVER PARTS OF MN AND WI ALONG/NORTH OF THE WARM
FRONT AS THE SWLY LOW LEVEL JET PROVIDES INCREASING WARM ADVECTION
LIFT.  THIS ACTIVITY IS EXPECTED TO SPREAD EWD/ESEWD DURING THE
OVERNIGHT HOURS AS THE LOW LEVEL JET VEERS WITH TIME AND WARM
ADVECTION ZONE SHIFTS TOWARD LOWER MI. FORECAST WIND PROFILES
EXHIBIT STRONG VEERING WITH HEIGHT...WITH SUFFICIENT VERTICAL SHEAR
WITHIN THE CLOUD LAYER TO SUPPORT ELEVATED SUPERCELLS. LARGE HAIL
WILL BE POSSIBLE WITH STRONGER CELLS...WITH ADDITIONAL THREAT FOR
STRONG WIND GUSTS WITH NEAR SURFACE-BASED STORMS CLOSE TO THE WARM
FRONT. THIS ACTIVITY IS LIKELY TO PERSIST THROUGH THE NIGHT AS IT
SPREADS ESEWD ACROSS THE LOWER GREAT LAKES AREA.

THERE IS ALSO A POSSIBILITY OF ISOLATED THUNDERSTORMS FORMING DURING
THE AFTERNOON IN THE WARM SECTOR...HOWEVER THE PRESENCE OF A WEAK
CAP IS LIKELY TO LIMIT THE OVERALL COVERAGE OF DEEP CONVECTION. 
SINCE THE STRONGER VERTICAL SHEAR EXTENDS SWD INTO PARTS OF MO AND
SRN IL...THERE IS A LOW CONDITIONAL PROBABILITY OF SEVERE WITH ANY
STORM THAT DEVELOPS.  THE CONVECTIVE POTENTIAL SOUTH OF THE WARM
FRONT SHOULD DIMINISH AFTER SUNSET.

..WEISS.. 04/12/2006