SWODY1
SPC AC 261630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT SAT JUN 26 2010
VALID 261630Z - 271200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF SOUTHEASTERN
SOUTH DAKOTA...NORTHEASTERN NEBRASKA...SOUTHWESTERN MINNESOTA AND
NORTHWESTERN IOWA...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE SLIGHT FROM THE
NORTH/CENTRAL PLAINS EWD INTO THE UPPER MS VALLEY...
...CENTRAL/NRN PLAINS...
WV IMAGERY AND MORNING ANALYSIS SHOW BROAD UPPER TROUGH SHIFTING EWD
FROM CENTRAL MT SWD INTO NRN UT...WHICH WAS ALSO AIDING IN THE
EJECTION OF ANOTHER IMPULSE NEWD THROUGH NERN CO. THESE TWO SYSTEMS
SHOULD BE PRIMARY CONTRIBUTORS FOR SEVERE THREAT THIS PERIOD. AT THE
SURFACE...A BROAD AREA OF SURFACE LOW PRESSURE WAS SITUATED OVER WRN
NEB/SD WITH A SURFACE TROUGH/FRONT EXTENDING SWD INTO WRN KS. AS
UPPER TROUGH APPROACHES FROM THE WEST... SURFACE LOW SHOULD
CONSOLIDATE AND DEEPEN SLIGHTLY AS IT SHIFTS EWD INTO SRN MN THIS
EVE AND WI OVERNIGHT. SUBTLE WARM FRONT/OUTFLOW BOUNDARIES...WITH
ONE EXTENDING FROM CENTRAL SD SEWD ALONG THE IA/NEB AND ANOTHER IN
FAR SRN MN...ARE EXPECTED TO CONSOLIDATE AND SHARPEN BY LATE
AFTERNOON IN SERN SD/SRN MN AS THE LOW MOVES EWD.
AT MID MORNING...MOSTLY CLOUDY SKIES AND A FEW CLUSTERS OF ELEVATED
STORMS WERE LOCATED ACROSS THE DAKOTAS...WITHIN WEAK WARM ADVECTION
REGIME. ALTHOUGH MUCAPES AROUND 1500 J/KG AND CLOUD BEARING VERTICAL
SHEAR MAY SUPPORT ISOLATED SEVERE HAIL INTO THE EARLY AFTERNOON
HOURS...THE GREATER SEVERE THREAT LIKELY WILL WAIT UNTIL LATER TODAY
AS STRONGER FORCING SPREADS IN FROM THE W AND SW AND GREATER
BOUNDARY LAYER DESTABILIZATION OCCURS.
THE MOST LIKELY AREA FOR INTENSE STORMS TO DEVELOP THIS AFTERNOON
WILL BE SERN SD/NERN NEB/SWRN MN AND NWRN IA...AS UPPER WAVE
APPROACHES FROM THE SW AND SURFACE BOUNDARY PROVIDES FOCUS FOR
CONVECTIVE DEVELOPMENT. ALSO...THIS IS AN AREA WHERE SKIES HAVE BEEN
SUNNY THROUGH THE MORNING AND MORE WARMING SHOULD RESULT IN EXTREME
INSTABILITY BY MID AFTERNOON...WITH MLCAPES APPROACHING 4000 J/KG.
ONCE SURFACE BASED STORMS DEVELOP...THE EXTREME INSTABILITY COMBINED
WITH EFFECTIVE SHEAR NEAR 50 KT WILL BE VERY FAVORABLE FOR INTENSE
SUPERCELLS. THOUGH THE GREATEST THREAT WILL BE VERY HAIL...BASEBALL
SIZED AND BIGGER...STRONGLY CURVED HODOGRAPHS IN THE LOWER 1-2 KM
INDICATES TORNADOES ARE ALSO LIKELY WITH DISCRETE
SUPERCELLS...ESPECIALLY WITHIN MODERATE RISK AREA. OVERNIGHT...AS
LOW LEVEL JET STRENGTHENS...CONVECTION MAY CONSOLIDATE INTO A
LINEAR MCS. LARGE HAIL AND WIND DAMAGE...AS WELL AS A TORNADO OR
TWO...SHOULD PERSIST AS ACTIVITY SPREADS EWD ACROSS PORTIONS OF
MN/WI/IA INTO EARLY SUNDAY.
OTHER STORMS ARE ALSO LIKELY TO DEVELOP/SPREAD EWD ACROSS THE
DAKOTAS SWD INTO NEB LATE TODAY AND TONIGHT...AND POSSIBLY NRN KS AS
UPPER TROUGH APPROACHES FROM THE WEST. THOUGH THE COMBINATION OF
CONVERGENCE/SHEAR AND INSTABILITY WILL NOT BE AS GREAT AS IN THE
MODERATE RISK AREA...MODERATE TO STRONG INSTABILITY AND BAND OF
40-50 KT MID LEVEL FLOW...WILL BE SUFFICIENT FOR SUPERCELLS WITH
SEVERE HAIL AND WIND DAMAGE. GIVEN THE MORNING CLOUDS ACROSS NERN
CO/WRN NEB AND EXPECTED SUBSIDENCE BEHIND DEPARTING UPPER
IMPULSE...ONLY VERY ISOLATED HIGH BASED STORMS ARE EXPECTED ACROSS
NERN CO...WRN KS AND FAR SERN WY LATE THIS AFTERNOON.
...IL/IN/OH...
OUTFLOW FROM OVERNIGHT MCS COULD PROVIDE A FOCUS FOR STORM
DEVELOPMENT LATER TODAY AS AIR MASS UNDERGOES DIURNAL
DESTABILIZATION. THE MID LEVEL FLOW WILL NOT BE PARTICULARLY STRONG
AND UPPER WAVE CURRENTLY MOVING THROUGH THE AREA MAY RESULT IN WEAK
SUBSIDENCE FOR THE NEXT FEW HOURS. HOWEVER... CONVERGENCE MAY
INCREASE BY EVENING AS LOW LEVEL JET SLOWLY STRENGTHENS TO 20 KT. IF
STORMS DEVELOP...INSTABILITY WOULD BE FAVORABLE FOR ISOLATED WIND
DAMAGE.
...SRN ATLANTIC COASTAL STATES WWD INTO OK...
VERY MOIST...WARM AND HUMID AIR MASS SHOULD RESULT IN SCATTERED
THUNDERSTORMS INTO THE EVENING HOURS. WHILE A FEW WET...SHORT LIVED
MICROBURSTS APPEAR LIKELY...WEAK MID LEVEL FLOW/SHEAR AND POORLY
DEFINED FOCUSING MECHANISMS MEANS THESE FEW EVENTS WOULD OCCUR
WITHIN A LARGE AREA...SO ONLY LOW WIND PROBABILITIES ARE FORECAST.
..IMY/SMITH.. 06/26/2010
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