SPC AC 111702
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1202 PM CDT WED JUN 11 2008
VALID 121200Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE WRN GREAT
LAKES...MID MS VALLEY...SRN PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN ND AND WRN MN...
...SYNOPSIS...
STRONG DEEP-LAYER CYCLONE IS FORECAST TO UNDERGO OCCLUSION WHILE
MOVING SLOWLY ENEWD ALONG THE U.S./CANADIAN BORDER FROM FAR NWRN ND
INTO EXTREME SRN MANITOBA ON THU. BY AFTERNOON...THE FRONT
ASSOCIATED WITH THIS SYSTEM SHOULD STRETCH FROM THE PRIMARY SURFACE
LOW...OVER NRN ND/U.S. BORDER AREA...SEWD TO WI THEN SWWD ACROSS ERN
IA TO MO AND SRN KS. GREATEST PROBABILITY OF SEVERE STORMS WILL
EXIST ALONG AND AHEAD OF THE FRONTAL ZONE. THE NRN SEGMENT OF THE
FRONT WILL MAKE STEADY EWD PROGRESS ACROSS THE WRN GREAT LAKES
REGION THROUGH THE PERIOD GIVEN EWD PROGRESSION OF MODEST MEAN-LAYER
WLY FLOW ACROSS THIS REGION. THE TRAILING SRN SEGMENT OF THE FRONT
IS FORECAST TO BECOME QUASI-STATIONARY ACROSS KS/OK AREA...POSSIBLY
PROVIDING A FOCUS FOR MCS DEVELOPMENT INTO EARLY FRIDAY MORNING OVER
THESE AREAS.
BROAD SUB-TROPICAL RIDGE AXIS WILL PERSIST ACROSS THE SRN AND SERN
STATES WITH A WEAK MID/UPPER LEVEL LOW SKIRTING THE SRN FLANK OF THE
RIDGE AXIS OVER THE NRN GULF. WEAK INHIBITION AND STRONG
HEATING/DESTABILIZATION WILL AGAIN LEAD TO SCATTERED PULSE STORMS
ACROSS THESE AREAS WITH A FEW STORMS CAPABLE OF WIND DAMAGE AND HAIL
EVENTS.
...WRN GREAT LAKES SWWD TO THE MID MS RIVER VALLEY...
OVERNIGHT CONVECTION ACROSS THE MO RIVER VALLEY EXPECTED TO SHIFT
EWD INTO INCREASINGLY UNSTABLE REGIME FROM WRN U.P. OF MI SWD ACROSS
WI/ERN IA/NRN IL AND MO. WHILE MARGINAL SVR HAIL WILL BE POSSIBLE
WITH MORNING STORMS...THE POTENTIAL FOR SVR HAIL/WIND IS LIKELY TO
INCREASE DURING THE AFTERNOON AND EVENING HOURS AS LIFT WITHIN
PRE-FRONTAL WARM CONVEYOR BELT SUSTAINS DEEP CONVECTION... AND
GREATER INSTABILITY IS REALIZED.
EXPECT NUMEROUS ORGANIZED STORMS/LINE SEGMENTS GIVEN SBCAPE IN
EXCESS OF 2000 J/KG AND DEEP LAYER SHEAR 30-50KT. A COUPLE OF
SUPERCELLS ALSO APPEAR POSSIBLE BUT PRIMARY MODE SHOULD BE LINEAR
GIVEN UNIDIRECTIONAL FLOW AND LINEAR FORCING ALONG THE ADVANCING
FRONT. AN ENHANCED WIND/TORNADO THREAT MAY EVOLVE ACROSS NRN IL/SERN
WI DURING THE AFTERNOON IF STRONG DESTABILIZATION CAN OCCUR AHEAD OF
ACCELERATING CONVECTIVE COLD POOLS ASSOCIATED WITH STRENGTHENING
DEEP-LAYER WIND FIELDS.
...MO TO KS/OK...
STRONG CAP AND WEAKER LARGE SCALE FORCING FOR ASCENT WILL PROBABLY
LIMIT STORM DEVELOPMENT ACROSS THESE AREAS UNTIL LATE
AFTERNOON/EARLY EVENING. TEMPERATURES WARMING WELL INTO THE 90S F IN
SRN AREAS...85-90 F FARTHER NORTH...COUPLED WITH HIGH THETA-E AIR
MASS...WILL YIELD SBCAPE IN EXCESS OF 2500 J/KG.
STRONG HEATING/MIXING NEAR THE FRONT AND SOME BACKGROUND ASCENT
WITHIN/BENEATH JET ENTRANCE REGION WILL AID IN OVERCOMING INHIBITION
AND PROMOTE CONVECTIVE DEVELOPMENT FROM MO SWWD TO NERN OK/SERN KS
THROUGH EARLY EVENING. VEERING WIND PROFILES IN THE LOWER 3KM AND
STRONG INSTABILITY WILL BE FAVORABLE FOR INTENSE SUPERCELLS CAPABLE
OF PRODUCING VERY LARGE HAIL AND HIGH WINDS. TORNADO POTENTIAL WILL
ALSO EXIST WITH INITIAL DEVELOPMENT... ESPECIALLY WITH CELLS ABLE TO
TRACK PREFERENTIALLY NEAR/ALONG STALLING FRONTAL ZONE NEAR KS/OK
BORDER WHERE LFC WILL BE LOWER AND STORMSCALE/MESOSCALE SHEAR WILL
BE LOCALLY ENHANCED.
LATEST GUIDANCE INDICATES ADDITIONAL STORM DEVELOPMENT IS POSSIBLE
AFTER DARK TO THE NORTH OF THE FRONT ACROSS KS. THIS SEEMS
REASONABLE GIVEN STRENGTHENING NOCTURNAL LLJ AND APPROACH OF LOW
AMPLITUDE SHORT WAVE TROUGH EMANATING OUT OF THE LARGER SCALE
TROUGH/LOW ACROSS THE ROCKIES AND NRN PLAINS. WHILE THIS ACTIVITY
MAY BE ROOTED ABOVE FRONTAL INVERSION...MAGNITUDE OF MOIST
INFLOW...LAPSE RATES...AND EFFECTIVE SHEAR...ALL APPEAR TO SUPPORT
SEVERE STORMS. INITIAL THREAT WILL BE LARGE HAIL WITH AN INCREASING
CHANCE FOR WIND DAMAGE POSSIBLY DEVELOPING IF AN MCS CAN EVOLVE FROM
THE OVERNIGHT CONVECTION.
...ERN ND/MN...
COLD TEMPERATURES ALOFT AND THE LIFT WITH UPPER LOW WILL CONTRIBUTE
TSTM DEVELOPMENT ACROSS THESE AREAS DURING THE AFTERNOON HOURS.
EFFECTIVE SHEAR OF 30-40 KT AND STEEPENING LOW/MID LEVEL LAPSE RATES
SHOULD FURTHER SUPPORT ORGANIZED ACTIVITY WITH SEVERAL HAIL EVENTS
LIKELY...AND PERHAPS EVEN A FEW STRONG CONVECTIVE WIND GUSTS.
..CARBIN.. 06/11/2008
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
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