SWODY1
SPC AC 311946
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0246 PM CDT TUE AUG 31 2010
VALID 312000Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS TO THE
UPPER MS VALLEY...
MINOR CHANGES HAVE BEEN APPLIED TO THE CNTRL HIGH PLAINS...NAMELY
THE UPSLOPE REGIONS OF NERN CO INTO NWRN KS. HAVE OPTED TO LOWER
SEVERE PROBABILITIES ACROSS THIS REGION WHERE MUCH DRIER BOUNDARY
LAYER AIRMASS HAS REPLACED EARLIER 50S SFC DEW POINTS. WITH
ADDITIONAL MIXING IT APPEARS THE THREAT FOR ROBUST UPDRAFTS CAPABLE
OF PRODUCING SEVERE WINDS/HAIL IS TOO MEAGER TO WARRANT PROBS.
FARTHER EAST ACROSS ERN NEB/IA/SRN MN...EXTENSIVE LOW CLOUDS HAVE
PRECLUDED SIGNIFICANT BOUNDARY LAYER HEATING ACROSS THIS REGION.
LATEST DIAGNOSTIC DATA DOES SUGGEST A NARROW WEDGE OF STEEPER LAPSE
RATES HAVE DEVELOPED FROM KS INTO EXTREME SWRN IA. THIS ZONE OF
INCREASED INSTABILITY SHOULD EVENTUALLY FEED STRENGTHENING UPDRAFTS
ACROSS THE WARM SECTOR. UNTIL THEN...WEAK FRONTAL ASCENT/WARM
ADVECTION HAS AIDED RECENT THUNDERSTORM DEVELOPMENT OVER NRN IA.
THIS ACTIVITY MAY STRUGGLE FOR A FEW HOURS BEFORE UPDRAFTS COUPLE
WITH HIGHER INSTABILITY FEED FROM THE SWRN HEAT SOURCE.
OTHERWISE...OUTLOOK WILL ONLY BE ADJUSTED TO ACCOUNT FOR LATEST
DIURNAL AND CONVECTIVE TRENDS.
..DARROW.. 08/31/2010
.PREV DISCUSSION... /ISSUED 1114 AM CDT TUE AUG 31 2010/
...CENTRAL PLAINS TO UPPER MS VALLEY THIS AFTERNOON AND EVENING...
WITH STRONG SYSTEM ROTATING NEWD ACROSS MANITOBA/ONTARIO THE LARGE
SCALE TROUGH FROM NRN ROCKIES EWD INTO THE PLAINS IS LOSING
AMPLITUDE. WHILE COLD FRONT CONTINUES EWD ACROSS UPPER MS
VALLEY...THE TRAILING PORTION WILL MOVE MORE SLOWLY SEWD ACROSS SRN
MN INTO ERN NEB THIS AFTERNOON/EVENING.
AXIS OF HIGH PWAT AROUND 2 INCHES EXTENDS FROM MO NNEWD ACROSS IA
INTO WI WHERE CURRENT ELEVATED CONVECTION IS OCCURRING. AS FRONT
ENCOUNTERS THIS MOIST PLUME WITH STRONG HEATING...MLCAPES WILL CLIMB
RAPIDLY THIS AFTERNOON AHEAD OF THE FRONT FROM WRN IA SWWD INTO SERN
NEB/NRN KS.
DEEP LAYER SHEAR WILL BE MARGINAL IN SUPPORT OF SEVERE THUNDERSTORMS
AS PRIMARY WESTERLIES REMAIN GENERALLY N OF MOST FAVORABLE
THERMODYNAMICS AND FRONTAL CONVERGENCE. HOWEVER GIVEN THE MLCAPES
AOA 3000 J/KG STILL EXPECT A BROAD WINDOW FROM MID AFTERNOON UNTIL
EVENING WHEN INTENSE MULTICELL/ISOLATED SUPERCELL DEVELOPMENT SHOULD
OCCUR ONCE HEATING DISSIPATES THE CINH.
DAMAGING WINDS WILL BE THE PRIMARY CONCERN...HOWEVER SUFFICIENT LOW
LEVEL VEERING SHEAR PROFILES COUPLED WITH THE INSTABILITY SUPPORT A
FEW SUPERCELLS SERN NEB INTO IA THRU THE EARLY EVENING ALONG WITH A
BRIEF TORNADO AND LARGE HAIL THREAT.
...CNTRL HI PLNS LATE THIS AFTN INTO TONIGHT...
WEAK...MARGINALLY MOIST POST-FRONTAL UPSLOPE FLOW MAY FOSTER THE
DEVELOPMENT OF A FEW HIGH BASED TSTMS ALONG THE NRN CO FRONT RANGE
AND/OR OVER THE ADJACENT HI PLNS BY EARLY EVE. AS STORMS
MOVE/DEVELOP EWD ALONG/N OF THE STALLING FRONT...HIGHLY
SHEARED/STEEP LAPSE RATE ENVIRONMENT ON SRN FRINGE OF THE WLYS MAY
YIELD A FEW STORMS CAPABLE OF MARGINALLY SVR HAIL/GUSTY WINDS.
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