[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 250600
SWODY2
SPC AC 250559

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT FRI AUG 25 2006

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS SAT AFTN/SAT EVE ACROSS PARTS
OF THE GREAT LAKES/UPR OH VLY....

...THERE IS A SLGT RISK OF SVR TSTMS LATE SAT AFTN/SAT EVE ACROSS
PARTS OF THE SRN PLAINS/OZARKS....

...THERE IS A SLGT RISK OF SVR TSTMS LATE SAT AFTN/SAT EVE...EAST OF
THE FRONT RANGE OF THE ROCKIES....

MODELS INDICATE THAT A SUBTLE WEAKENING OF THE CENTRAL/SOUTHERN U.S.
SUBTROPICAL RIDGE...WHICH HAS BEEN UNDERWAY THE PAST WEEK OR
SO...WILL CONTINUE THROUGH THIS FORECAST PERIOD...IN RESPONSE TO
PROGRESSION OF SHORT WAVE TROUGHS WITHIN THE POLAR WESTERLIES. THE
PRIMARY BELT WILL GENERALLY REMAIN JUST NORTH OF THE CANADIAN/U.S.
BORDER...WITH A SIGNIFICANT EMBEDDED SHORT WAVE PROGGED EAST OF
MANITOBA EARLY SATURDAY THROUGH MUCH OF ONTARIO BY 12Z SUNDAY. 
PHASING OF THIS FEATURE WITH AN IMPULSE IN A WEAKER SOUTHERN BELT IS
FORECAST TO OCCUR LATE SATURDAY THROUGH SATURDAY EVENING ACROSS THE
GREAT LAKES/OHIO VALLEY REGION.  MEANWHILE...A MORE SIGNIFICANT
SOUTHERN BRANCH TROUGH SEEMS LIKELY TO LAG TO THE WEST...BUT STILL
CONTINUE TO SLOWLY DIG SOUTHEAST OF THE NORTHERN GREAT BASIN INTO
THE CENTRAL ROCKIES.

FORCING WITH THE LARGE-SCALE FEATURES...SEASONABLY MOIST LOW-LEVEL
ENVIRONMENT AND AN INFLUX OF MOISTURE FROM THE LOWER LATITUDE
EASTERN PACIFIC WILL PROBABLY ALL CONTRIBUTE TO A CONSIDERABLE
AMOUNT OF CONVECTIVE ACTIVITY SATURDAY/SATURDAY NIGHT. WEAK FRONTAL
SURGE INTO THE OHIO VALLEY AND SOUTHERN PLAINS WILL PROVIDE ONE
FOCUS FOR ACTIVITY...AS WILL A BAROCLINIC ZONE ACROSS THE LOWER
GREAT LAKES/NORTHERN MID ATLANTIC REGION...ASSOCIATED WITH A
RETREATING SURFACE RIDGE.  A WEAK IMPULSE MIGRATING AROUND THE
SOUTHWESTERN PERIPHERY OF MID-LEVEL HIGH CENTER OVER THE MID
ATLANTIC STATES WILL CONTRIBUTE TO SCATTERED AFTERNOON/EVENING
STORMS ACROSS MUCH OF THE GULF STATES. AND...DIURNAL THUNDERSTORM
ACTIVITY WILL BECOME FOCUSED PRIMARILY ACROSS THE HIGHER TERRAIN OF
THE INTERMOUNTAIN WEST/ROCKIES.

...LOWER GREAT LAKES/OHIO VALLEY...
LACK OF COLDER AIR ALOFT/STEEPER MID-LEVEL LAPSE RATES WILL BE THE
PRIMARY LIMITING FACTOR TO SEVERE POTENTIAL SATURDAY.  POTENTIAL
CLOUD COVER IS ALSO A CONCERN...BUT CONSIDERABLE HEATING IS EXPECTED
ACROSS MUCH OF INDIANA/OHIO INTO PARTS OF WESTERN
PENNSYLVANIA...WHERE VEERING WINDS WITH HEIGHT BENEATH WEAK TO
MODERATE WESTERLY MID-LEVEL FLOW WILL BE MARGINALLY SUFFICIENT FOR
SUPERCELLS.  SHEAR WILL BE STRONGER...BUT WITH WEAKER
INSTABILITY...ACROSS LOWER MICHIGAN...WHERE STORMS COULD INITIATE BY
EARLY SATURDAY AFTERNOON.  THEN...AS LARGE-SCALE FORCING FOR UPWARD
VERTICAL MOTION INCREASES LATE SATURDAY AFTERNOON INTO SATURDAY
EVENING...STRONG/SEVERE STORMS ARE EXPECTED TO INCREASE ACROSS THE
UPPER OHIO VALLEY.  ISOLATED TORNADOES ARE POSSIBLE...BUT...AT THIS
TIME...IT APPEARS LARGE HAIL/DAMAGING WIND GUSTS WILL BE PRIMARY
THREATS BEFORE SEVERE POTENTIAL DIMINISHES ACROSS THE LOWER GREAT
LAKES REGION LATE SATURDAY EVENING.

...SOUTHERN PLAINS/OZARK PLATEAU...
STABILIZING INFLUENCE OF WEAKENING CONVECTIVE CLUSTER EXPECTED ALONG
FRONT ACROSS THE EAST CENTRAL PLAINS/OZARK PLATEAU EARLY SATURDAY IS
A CONCERN FOR SEVERE POTENTIAL.  AT THE PRESENT TIME...IT APPEARS
STRONGEST DESTABILIZATION WILL OCCUR SOUTH OF SURFACE BOUNDARY...IN
THE WAKE OF THIS FEATURE...AS IT SHIFTS EASTWARD THROUGH THE MIDDLE
MISSISSIPPI/LOWER OHIO VALLEY. LOW-LEVEL CONVERGENCE ALONG FRONT
AND/OR WARM ADVECTION ALONG/NORTH OF PRE-FRONTAL THERMAL RIDGE WILL
AID CONVECTIVE DEVELOPMENT LATE SATURDAY AFTERNOON/EVENING...FROM
PARTS OF NORTH CENTRAL OKLAHOMA INTO THE OZARKS.  VERTICAL SHEAR
WILL BE WEAK...BUT VERY WARM DEEP MIXED BOUNDARY WITH CAPE AROUND
2000 J/KG WILL BE SUPPORTIVE OF VIGOROUS STORMS WITH POTENTIAL FOR
STRONG DOWNBURSTS...AND POTENTIALLY DAMAGING SURFACE WINDS.

...GREAT BASIN/CENTRAL HIGH PLAINS...
DRYING/WEAK INSTABILITY IS EXPECTED TO BE A LIMITING FACTOR FOR
SEVERE POTENTIAL NEAR COLD CORE OF UPPER TROUGH...FROM PARTS OF
NORTHERN UTAH INTO SOUTHWEST WYOMING/NORTHWEST COLORADO...EARLY
SATURDAY.  HOWEVER...DESTABILIZATION IN MOIST UPSLOPE FLOW REGIME
ALONG AND TO THE LEE OF THE FRONT RANGE OF THE ROCKIES IS EXPECTED
TO BE SUFFICIENT FOR VIGOROUS CONVECTIVE DEVELOPMENT LATE SATURDAY
AFTERNOON AND EVENING. LOW/MID-LEVEL FLOW WILL BE WEAK...BUT
VEERING WITH HEIGHT BENEATH STRONG SOUTHWESTERLY HIGH LEVEL FLOW
WILL PROVIDE FAVORABLE HODOGRAPHS FOR SUPERCELLS...ENHANCING RISK
FOR LARGE HAIL/DAMAGING WINDS...POSSIBLY A TORNADO OR TWO.

..KERR.. 08/25/2006