ACUS02 KWNS 271732
SWODY2
SPC AC 271730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED JUL 27 2011

VALID 281200Z - 291200Z

....THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS TO THE
MIDWEST/GREAT LAKES REGION...

....SYNOPSIS...
THE TREND TOWARD LOWER AMPLITUDE WESTERLIES OVER THE NORTHERN TIER
WILL CONTINUE INTO THURSDAY AS AN EXTENSIVE/WEST-EAST ELONGATED
UPPER RIDGE PERSISTS OVER THE SOUTHERN HALF OF THE CONUS. AT THE
SURFACE...A WEAK COLD FRONT WILL SPREAD SOUTHEASTWARD OVER THE
MIDWEST/GREAT LAKES REGION...WHILE THE CENTRAL HIGH PLAINS PORTION
OF THE FRONT REMAINS QUASI-STATIONARY.

....NORTHEAST STATES/GREAT LAKES/MIDWEST TO CENTRAL PLAINS...
IT APPEARS THAT SCATTERED/POTENTIALLY A FEW CLUSTERS OF TSTMS WILL
BE ONGOING THURSDAY MORNING WITHIN A CORRIDOR ACROSS LOWER MI AND
ADJACENT NORTHERN INDIANA/OH TO THE LOWER GREAT LAKES. AN EARLY DAY
SEVERE THREAT IS GENERALLY NOT EXPECTED AS THIS ACTIVITY MOVES INTO
A WEAKER INSTABILITY ENVIRONMENT...ALTHOUGH GUIDANCE SUCH AS THE 12Z
NAM LENDS CREDENCE TO A POTENTIAL PERSISTENCE OF THIS ACTIVITY
ACROSS THE NORTHEAST STATES/TOWARD THE ATLANTIC SEABOARD.

OTHERWISE...DETAILS OF DIURNAL CONVECTIVE DEVELOPMENT ALONG THE
MAJORITY OF THE SLOW SOUTHEASTWARD-MOVING EFFECTIVE FRONTAL ZONE ARE
A BIT UNCERTAIN OWING TO RELATIVELY NEBULOUS LARGE SCALE FORCING FOR
ASCENT. NONETHELESS...A MOIST AIRMASS/CONVERGENCE IN VICINITY OF THE
EFFECTIVE SURFACE FRONT WILL BE SUFFICIENT FOR ISOLATED TO SCATTERED
TSTM DEVELOPMENT DURING THE AFTERNOON/EARLY EVENING. THIS INCLUDES A
NORTHEAST-SOUTHWEST ORIENTED CORRIDOR ACROSS THE GREAT LAKES
REGION/UPPER MS VALLEY/MIDWEST TO CENTRAL PLAINS...INCLUDING THE
LAKE MI GENERAL VICINITY AND SOUTHERN/EASTERN PORTIONS OF IA AND
NORTHERN MO INTO KS.

MUCH OF THE EFFECTIVE SURFACE FRONT WILL COINCIDE WITH THE SOUTHERN
EXTENT OF 20-30 KT WESTERLIES ALOFT...WITH POTENTIAL FOR POCKETS OF
MODERATE TO STRONG INSTABILITY /2000-3500 J PER KG SBCAPE/
ALONG/SOUTH OF THE SURFACE FRONT. SUCH A SCENARIO WILL BE CONDUCIVE
FOR MULTICELLS CAPABLE OF WIND DAMAGE AND PERHAPS SOME SEVERE HAIL
PRIMARILY THURSDAY AFTERNOON/EARLY EVENING.

FARTHER SOUTHWEST INTO KS...ALTHOUGH THE MID/HIGH LEVEL WINDS/SHEAR
WILL BE WEAKER IN PROXIMITY TO THE UPPER RIDGE...A HOT BOUNDARY
LAYER SHOULD ALSO SUPPORT STORMS WITH DAMAGING WINDS.

....NORTH-CENTRAL HIGH PLAINS...
CURRENT THINKING IS THAT AN MCS WILL BE ONGOING ACROSS THE REGION
THURSDAY MORNING...MOST LIKELY ACROSS PORTIONS OF WESTERN
SD/NORTHERN NEB. SUCH MCS POTENTIAL PROVIDES A DEGREE OF UNCERTAINTY
REGARDING THE EFFECTIVE LOCATION OF THE FRONTAL ZONE...AS WELL AS
THE SUBSEQUENT DEGREE OF DIURNAL DESTABILIZATION GIVEN POTENTIAL FOR
EARLY DAY CLOUD COVER/PRECIPITATION. ASIDE FROM WEAK LOW LEVEL
UPSLOPE...LARGE SCALE FORCING FOR ASCENT IS ALSO EXPECTED TO BE
RELATIVELY NEBULOUS AROUND PEAK HEATING.

THAT SAID...A MOIST AIRMASS/WEAK UPSLOPE SHOULD YIELD ISOLATED TO
SCATTERED TSTM DEVELOPMENT DURING THE AFTERNOON/EVENING. SUCH
DEVELOPMENT WOULD BE MOST PROBABLE IN VICINITY OF ANY RESIDUAL
OUTFLOW...SOUTHERN/WESTERN FRINGES OF THE EARLY DAY STORMS...AND
TERRAIN FAVORED AREAS SUCH AS THE BLACK HILLS/EASTERN WY. VEERING
WIND PROFILES/SUFFICIENT INSTABILITY...AGAIN ESPECIALLY ON THE
SOUTHERN AND WESTERN FRINGES OF ANY EARLY DAY MCS AND ASSOCIATED
CLOUDINESS...WILL SUPPORT SUSTAINED STORMS/SOME SUPERCELLS CAPABLE
OF SEVERE HAIL/WIND.

....GULF COAST STATES...
A RELATIVE WEAKNESS IN THE RIDGE ALOFT IN CONJUNCTION WITH A VERY
MOIST AIRMASS /2+ INCH PW/ WILL RESULT IN SCATTERED TO NUMEROUS
DIURNALLY-AIDED TSTMS ACROSS THE REGION. WITHIN A WEAKLY SHEARED
REGIME...A FEW OF THE STRONGEST STORMS THURSDAY AFTERNOON/EARLY
EVENING WILL BE CAPABLE OF PULSE-TYPE MICROBURSTS WITH LOCALIZED
WIND DAMAGE.

...GUYER.. 07/27/2011

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