[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 250557
SWODY1
SPC AC 250556

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT FRI AUG 25 2006

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE WRN GREAT
LAKES/UPPER MIDWEST TO SRN PLAINS/HIGH PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE WRN GREAT
LAKES FROM PA/NY TO NRN NJ...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL
ROCKIES...

...SYNOPSIS...
RELATIVELY HIGH-AMPLITUDE FLOW REGIME ACROSS SRN CANADA/NRN U.S.
WILL MAINTAIN A BELT OF MODERATE CYCLONIC FLOW ACROSS THE UPPER MS
VALLEY/WRN GREAT LAKES REGIONS THROUGH TODAY...WHILE SHARP
DOWNSTREAM RIDGE BUILDS ACROSS ONTARIO AND WRN QUEBEC. WEAKER
DOWNSTREAM IMPULSES...UNDERCUTTING THE RIDGE AXIS...WILL TRAVEL SEWD
IN A BAND OF MODEST WNWLY MID LEVEL FLOW FROM THE ERN GREAT
LAKES...ACROSS PA/NY...TO SRN NEW ENGLAND AND NJ. IN THE WEST...A
POSITIVE-TILT UPPER TROUGH WILL DIG SEWD OVER THE NRN GREAT BASIN
WITH HEIGHT FALLS AND DIFFLUENT MID/UPPER LEVEL FLOW SPREADING
ACROSS THE NRN/CNTRL ROCKIES.

SURFACE LOW ASSOCIATED WITH THE UPPER MS VALLEY/GREAT LAKES TROUGH
WILL DEVELOP GENERALLY EWD ALONG A WARM FRONT FROM WI TO LOWER MI AS
TRAILING COLD FRONT MAKES RELATIVELY SLOW PROGRESS EWD/SEWD ACROSS
IA AND THE UPPER MIDWEST THROUGH SATURDAY MORNING. WRN EXTENSION OF
THE FRONT WILL MOVE A BIT FASTER ACROSS THE SCNTRL PLAINS...AND PUSH
 WWD/SWWD INTO THE HIGHER TERRAIN FROM WY SWD ACROSS CO.

A QUASI-STATIONARY WARM FRONTAL ZONE...ALIGNED WITH THE DEEP-LAYER
WNWLY FLOW FROM THE LOWER/ERN GREAT LAKES TO SRN NEW ENGLAND/NJ WILL
PROVIDE A NARROW CORRIDOR FOR ASCENT ACROSS THESE REGIONS THROUGH
THE PERIOD.

...UPPER MIDWEST/GREAT LAKES...
WARM AND VERY MOIST AIR MASS WILL CONTINUE TO BE INCORPORATED INTO
ZONE OF PERSISTENT ASCENT AHEAD OF SURFACE LOW AND COLD FRONT
THROUGH THE AFTERNOON. DAYTIME HEATING COUPLED WITH 65-75F DEWPOINTS
WILL CONTRIBUTE TO MODERATE TO STRONG AFTERNOON DESTABILIZATION WITH
MLCAPES OF 1500-3500 J/KG EXPECTED FROM CNTRL SRN WI/NRN IL SWWD
ACROSS ERN IA. GIVEN WIDESPREAD CONVECTIVE DEBRIS BUT PERSISTING
LIFT NORTH OF THE WARM FRONT...FROM CNTRL/NRN WI ACROSS MUCH OF
MI...ELEVATED TSTMS CAPABLE OF MARGINALLY SEVERE HAIL MAY CONTINUE
THROUGH THE DAY FRIDAY OVER THESE AREAS.

MORE INTENSE...SURFACE-BASED STORM DEVELOPMENT APPEARS INCREASINGLY
LIKELY BY AFTERNOON FROM VICINITY OF SURFACE LOW SWD ALONG COLD
FRONT FROM CNTRL/SRN WI INTO NRN IL AS HEATING AND LARGE-SCALE
FORCING FOR ASCENT EFFECTIVELY ERODE THE CAP. MODEST WLY FLOW ATOP
THE DESTABILIZING AIR MASS WILL PROVIDE MORE THAN ADEQUATE VERTICAL
SHEAR FOR SUPERCELL STORMS AND PERHAPS BOWING LINE SEGMENTS CAPABLE
OF BOTH LARGE HAIL AND DAMAGING WINDS. TORNADO POTENTIAL APPEARS TO
BE SLIGHTLY LOWER THAN THURSDAY WITH WEAKER/VEERED LOW LEVEL FLOW
NEAR THE FRONT. HOWEVER...BETTER POTENTIAL FOR A TORNADO OR TWO MAY
EVOLVE FROM STORMS DEVELOPING NEAR SURFACE LOW AND MOVING ALONG THE
WARM FRONT WHERE LOW-LEVEL SHEAR WILL BE ENHANCED. CELLS
ENCOUNTERING POSSIBLE LAKE BREEZE BOUNDARY ACROSS ERN WI MAY ALSO
POSE A THREAT FOR A BRIEF TORNADO OR TWO.

FARTHER SW ALONG THE ADVANCING COLD FRONT...FROM ERN IA INTO ERN MO
AND IL...DEEP LAYER SHEAR WILL DIMINISH. HOWEVER...STRONG
DESTABILIZATION WILL DEVELOP BENEATH STOUT CAP. FRONTAL CIRCULATION
MAY BE SUFFICIENT TO OVERCOME THE CAP WITH A FEW INTENSE STORMS
POSSIBLE ACROSS THESE AREAS FROM LATE AFTERNOON INTO THE EVENING.
ISOLATED HAIL AND STRONG/DAMAGING WINDS COULD ACCOMPANY THIS
ACTIVITY.

...KS SWWD/WWD ACROSS THE PNHDLS INTO THE SRN HIGH PLAINS...
STEEPENING LOW THROUGH MID-LEVEL LAPSE RATES AND MOIST BOUNDARY
LAYER WILL COEXIST ALONG AND NORTH OF SURFACE FRONT/WIND SHIFT
SETTLING SOUTH INTO THESE AREAS DURING THE AFTERNOON. MLCAPES OF
1500-2500 J/KG AND LOW LEVEL CONVERGENCE/MIXING ALONG THE FRONT WILL
LEAD TO INCREASING TSTM COVERAGE AND INTENSITY. THIS WILL OCCUR
COINCIDENT WITH A SLIGHT INCREASE IN SWLY MID LEVEL FLOW...AND ATOP
LOW LEVEL ELY FLOW...THUS PROVIDING AN ENVIRONMENT WITH MARGINALLY
SUPPORTIVE SHEAR FOR ORGANIZED AND PERSISTENT STORMS. LATEST
GUIDANCE SUGGESTS THAT THIS CONVECTION WILL CONTINUE WELL INTO THE
EVENING AND POSSIBLY EVOLVE INTO AN MCS ACROSS PARTS OF SRN KS/NRN
OK. LOW LEVEL MASS INFLOW AND DEGREE OF INSTABILITY SHOULD SUSTAIN A
SEVERE HAIL/WIND THREAT FROM THIS CONVECTION ACROSS THESE AREAS
THROUGH EARLY SATURDAY.

...NCNTRL ROCKIES...
HEIGHT FALLS...DIFFLUENT MID LEVEL FLOW...AND LOW LEVEL UPSLOPE FLOW
WILL SPREAD ACROSS PARTS OF NRN UT/WRN WY AND CO DURING THE PERIOD
OF PEAK HEATING. AS LARGE SCALE ASCENT IMPINGES ON SUBTROPICAL
MOISTURE PLUME ACROSS THE AREA...STEEP LAPSE RATES AND MOISTENING
WILL LEAD TO SUFFICIENT INSTABILITY FOR STRONG TO SEVERE STORMS.
RELATIVELY HIGH-BASED SUPERCELLS WILL POSE A THREAT FOR HAIL AND
HIGH WINDS.

...ERN GREAT LAKES ACROSS NY/PA TO NJ...
NAM AND GFS INDICATE THAT SHORT WAVE IMPULSE UNDERCUTTING RIDGE AXIS
ACROSS SRN ONTARIO WILL SPREAD EAST AND ENHANCE ASCENT ALONG THE
STATIONARY FRONTAL ZONE FROM LAKE ERIE ACROSS NY/PA. VERTICAL SHEAR
ALONG THE SURFACE FRONT WILL REMAIN QUITE FAVORABLE FOR SUPERCELLS
THROUGH THE PERIOD GIVEN THE DEVELOPMENT AND MAINTENENCE OF
CONVECTION. MODELS AGREE THAT MOST FAVORABLE JUXTAPOSITION OF
DESTABILIZATION...FORCING...AND SHEAR MAY EVOLVE FROM WRN NY ACROSS
NCNTRL PA THROUGH EARLY EVENING. SUPERCELL STORMS ACROSS THESE AREAS
COULD BE CAPABLE OF PRODUCING HAIL AND POSSIBLY A TORNADO OR TWO.

..CARBIN/GUYER.. 08/25/2006