[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 241727
SWODY2
SPC AC 241726

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT THU AUG 24 2006

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE UPPER
MIDWEST/GREAT LAKES REGION...

...THERE IS A SLGT RISK OF SVR TSTMS OVER KS INTO NRN OK...

...SYNOPSIS...

STRONG SHORT WAVE TROUGH NOW MOVING INTO THE WRN DAKOTAS IS FORECAST
TO WEAKEN DURING THE DAY TWO PERIOD AS IT TRANSLATES EWD THROUGH THE
GREAT LAKES REGION...UNDERCUTTING AMPLIFIED RIDGE OVER ONTARIO. 
WEAKER DOWNSTREAM IMPULSES WILL SHIFT EWD ALONG SRN PERIPHERY OF ERN
CANADA LONG WAVE TROUGH ACROSS THE LOWER GREAT LAKES AND CNTRL/SRN
NEW ENGLAND.  MEANWHILE TO THE W...UPSTREAM TROUGH WILL EVOLVE INTO
A CUTOFF LOW OVER THE ERN GREAT BASIN.

IN THE LOW-LEVELS...SURFACE LOW ASSOCIATED WITH THE GREAT LAKES
SHORT WAVE TROUGH WILL DEVELOP EWD FROM SRN WI ACROSS LOWER MI INTO
SWRN ONTARIO WITH TRAILING COLD FRONT PUSHING SWD THROUGH THE LOWER
MO VALLEY AND CNTRL HIGH PLAINS.  ATTENDANT WARM FRONT IS FORECAST
TO LIFT NWD THROUGH LOWER MI WITH ERN EXTENSION OF THIS BOUNDARY
REMAINING MORE QUASI-STATIONARY FROM THE LOWER GREAT LAKES SEWD TO
THE MIDDLE ATLANTIC COAST.

...UPPER MIDWEST/GREAT LAKES REGION...

WARM SECTOR AIR MASS IS FORECAST TO REMAIN QUITE MOIST FRIDAY AHEAD
OF SURFACE LOW AND COLD FRONT WITH DEWPOINTS IN THE MID 60S TO LOWER
70S.  WHILE MID-LEVEL LAPSE RATES ARE NOT FORECAST TO BE
PARTICULARLY STEEP...DAYTIME HEATING COUPLED WITH THIS
BOUNDARY-LAYER MOISTURE ARE EXPECTED TO CONTRIBUTE TO MODERATE
AFTERNOON INSTABILITY WITH MLCAPES OF 1500-3000 J/KG DEVELOPING FROM
SRN WI/NRN IL WWD INTO NRN MO. ELEVATED TSTMS CAPABLE OF MARGINALLY
SEVERE HAIL WILL LIKELY PERSIST THROUGH THE DAY FRIDAY N OF WARM
FRONT OVER NRN WI/THE UP/NRN LOWER MI...DRIVEN BY LOW-LEVEL WAA
AHEAD OF WEAKENING SHORT WAVE TROUGH.

POTENTIALLY MORE INTENSE...SURFACE-BASED STORM DEVELOPMENT WILL
BECOME INCREASINGLY LIKELY BY AFTERNOON FROM VICINITY OF SURFACE LOW
SWD ALONG COLD FRONT FROM CNTRL/SRN WI INTO NRN IL AS DIABATIC
HEATING AND LARGE-SCALE FORCING FOR ASCENT EFFECTIVELY ERODE THE
CAP.  PRESENCE OF 70-80 KT UPPER JET STREAK ACCOMPANYING SHORT WAVE
TROUGH WILL RESULT IN SUFFICIENT DEEP LAYER SHEAR FOR SUPERCELLS AND
BOWING STRUCTURES CAPABLE OF MAINLY LARGE HAIL AND DAMAGING WINDS. 
APPEARS BEST POTENTIAL FOR A TORNADO OR TWO WILL BE WITH ANY STORMS
DEVELOPING NEARER TO SURFACE LOW AND ATTENDANT WARM FRONT WHERE
LOW-LEVEL SHEAR WILL BE ENHANCED FROM E-CNTRL WI EWD INTO CNTRL OR
NRN LOWER MI.

...KS...

THERE REMAINS SOME UNCERTAINTY AS TO THE POSITION OF TRUE SYNOPTIC
FRONT AND ANY OUTFLOW BOUNDARIES REMNANT FROM CONVECTION DEVELOPING
DURING THE LATTER HALF OF THE DAY ONE PERIOD.  LATEST SHORT TERM
MODEL GUIDANCE DOES SUGGEST THAT STEEP LOW/MID-LEVEL LAPSE AND MOIST
BOUNDARY-LAYER CONDITIONS WILL BECOME CO-LOCATED ACROSS REGION NEAR
OR JUST N OF SURFACE FRONT FRIDAY AFTERNOON...CONTRIBUTING TO
MLCAPES OF 1500-2500 J/KG.  IT APPEARS THAT DAYTIME
HEATING...LOW-LEVEL CONVERGENCE ALONG PRE-EXISTING BOUNDARIES AND
LARGER-SCALE FORCING IN RIGHT ENTRANCE REGION OF UPPER JET STREAK
OVER THE NRN PLAINS WILL ALL CONTRIBUTE TO AN INCREASE IN
SURFACE-BASED STORM ACTIVITY DURING THE AFTERNOON AND EVENING 
HOURS.

WHILE ONLY 15-25 KT MID-LEVEL FLOW IS FORECAST...UPPER TROPOSPHERIC
WIND FIELDS WILL REMAIN 50-60 KTS.  WHEN COUPLED WITH ELY LOW-LEVEL
WINDS N OF SURFACE FRONT...EFFECTIVE BULK SHEAR OF 30-40 KTS IS
FORECAST...SUPPORTIVE OF ORGANIZED...ROTATING UPDRAFTS CAPABLE OF
SEVERE HAIL AND LOCALLY DAMAGING WINDS.

...CNTRL HIGH PLAINS...

VERTICAL SHEAR WILL REMAIN SUPPORTIVE OF UPDRAFT ROTATION NWWD INTO
CNTRL WY WITHIN POST-FRONTAL UPSLOPE REGIME.  HOWEVER...PRIMARY
FACTOR LIMITING A MORE ORGANIZED SEVERE THREAT WILL BE LIMITED
INSTABILITY.  A FEW POCKETS OF AT LEAST WEAK INSTABILITY /MLCAPES OF
250-500 J/KG/ WILL LIKELY DEVELOP BY AFTERNOON AND IF STORMS CAN
DEVELOP AND BECOME SUSTAINED...THEN POTENTIAL WOULD EXIST FOR SOME
HAIL AND GUSTY WINDS.

...LOWER GREAT LAKES TO THE MID ATLANTIC COAST...

CONSIDERABLE UNCERTAINTY EXISTS WITH REGARD TO CONVECTIVE EVOLUTION
DOWNSTREAM FROM CNTRL GREAT LAKES LOW ALONG ATTENDANT WARM FRONT OR
QUASI-STATIONARY BOUNDARY.  AS MENTIONED ABOVE...IT APPEARS THAT
SEVERAL WEAK IMPULSES WILL ROTATE THROUGH THE BASE OF ERN CANADA
LONG WAVE TROUGH...THE TIMING OF WHICH REMAINS DIFFICULT.  IN
ADDITION...THE DEGREE OF AIR MASS DESTABILIZATION REMAINS IN
QUESTION.  VERTICAL SHEAR INVOF THE SURFACE FRONT WILL REMAIN QUITE
FAVORABLE FOR SUPERCELLS THROUGH THE PERIOD GIVEN THE DEVELOPMENT
AND MAINTENENCE OF MOIST DEEP CONVECTION.  ONCE FINER SCALE DETAILS
BECOME MORE CLEAR...PORTIONS OF REGION MAY NEED TO BE UPGRADED TO A
SLIGHT RISK IN SUBSEQUENT DAY ONE OUTLOOKS.

..MEAD.. 08/24/2006