SWODY1
SPC AC 082000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT MON JUN 08 2009
VALID 082000Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS NEWD INTO
THE GREAT LAKES...
...THERE IS A SLGT RISK OF SVR TSTMS NEAR THE HIGHER TERRAIN OF SERN
WY AND NERN CO...
...NERN CO/SERN WY...
STORMS HAVE FORMED OVER THE HIGHER TERRAIN...BUT CLOUDS HAD SLOWED
HEATING CONSIDERABLE ACROSS MUCH OF NERN CO...MID 50S AT
19Z...RESULTING IN A VERY STABLE BOUNDARY LAYER. CLOUDS WILL
EVENTUALLY DISSIPATE...BUT NOT SURE BOUNDARY LAYER WILL HAVE
SUFFICIENT TIME TO DESTABILIZE. THEREFORE...HAVE CARVED MUCH OF NERN
CO OUT OF SLIGHT RISK. HOWEVER...MAINTAINING SLIGHT RISK FOOTHILLS
AND PALMER DIVIDE SINCE DEEP LAYER SHEAR AND SUFFICIENT INSTABILITY
IS IN PLACE FOR SUPERCELLS.
...CENTRAL AND SRN APPALACHIANS...
NUMEROUS STORMS HAVE FORMED ALONG THE SPINE OF THE CENTRAL/SRN
APPALACHIANS...POSSIBLE DUE TO AN INTERACTION WITH AN EARLIER
GRAVITY WAVE. DESPITE WEAK SHEAR...MLCAPES FROM 1500 TO 2500 J/KG
WILL SUPPORT AN ISOLATED DAMAGING WIND/HAIL THREAT THROUGH THE
AFTERNOON.
...CENTRAL OK NEWD INTO SWRN MO...
STILL MAINTAINING SLIGHT RISK...THOUGH CAP IS HOLDING STRONG DUE TO
INCREASED CUMULUS CLOUD DEVELOPMENT AND WEAK FORCING. STORMS LOOKING
MORE UNLIKELY...BUT SHOULD A STORM DEVELOP...MLCAPES NEARING 4000
J/KG AND 30-40 KT DEEP LAYER SHEAR WOULD BE FAVORABLE FOR SUPERCELLS
WITH HAIL/WIND DAMAGE.
...NWRN TX...
CU HAS RECENTLY DEVELOPED BETWEEN LBB AND MWL WHERE STRONG SOLAR
INSOLATION HAS RAISED TEMPERATURES INTO THE MID/UPPER 90S. EXTREME
INSTABILITY AND DEEP LAYER SHEAR AT 40 TO 50 KT WILL SUPPORT INTENSE
SUPERCELLS WITH A THREAT FOR VERY LARGE HAIL. ALSO...STRONG OUTFLOW
PRODUCTION MAY RESULT IN A SMALL DAMAGING WIND MCS TO MOVE ACROSS
PORTIONS OF NRN TX/SRN OK THIS EVENING.
..IMY.. 06/08/2009
.PREV DISCUSSION... /ISSUED 1130 AM CDT MON JUN 08 2009/
...NW TX/OK/MO/AR THIS AFTERNOON INTO EARLY TONIGHT...
REGIONAL 12Z SOUNDINGS CONTINUE TO SHOW A WARM EML OVER THE MOIST
BOUNDARY LAYER WITH DEW POINTS IN THE MID-UPPER 60S...AND STRONG
SURFACE HEATING IS EXPECTED ALONG/S OF THE COLD FRONT DRIFTING SWD
INTO NW TX AND CENTRAL/NE OK. THE MORE PROBABLE AREA FOR THE CAP TO
WEAKEN WILL BE THE SOMEWHAT HIGHER ELEVATION AREAS OF NW TX /JUST E
OF THE CAPROCK/ WHERE AFTERNOON TEMPERATURES GET WELL INTO THE 90S
AND MLCAPE EXCEEDS 3000 J/KG. DEEP LAYER VERTICAL SHEAR WILL BE
FAVORABLE FOR SUPERCELLS NEAR THE FRONT AND BENEATH A BELT OF 40+ KT
MID LEVEL WSWLY FLOW...WHILE THE STEEP LAPSE RATES/STRONG
INSTABILITY WILL FAVOR LARGE HAIL AS THE PRIMARY SEVERE THREAT FROM
LATE AFTERNOON INTO EARLY TONIGHT. SOME OF THE CONVECTION MAY
EVOLVE INTO A SMALL CLUSTER OR TWO...WITH SOME POTENTIAL FOR THE
STORMS TO SPREAD EWD/NEWD ALONG THE STALLED FRONT INTO SRN OK/N TX
EARLY TONIGHT.
THERE WILL ALSO BE SOME POTENTIAL FOR ISOLATED STORM DEVELOPMENT
FARTHER NE ALONG THE FRONT THIS AFTERNOON FROM NE OK INTO SRN MO/NRN
AR. THIS AREA WILL BE WELL REMOVED FROM THE PRIMARY MID LEVEL
TROUGH MOVING NEWD OVER IA/IL...AND NEAR THE NE EDGE OF THE STRONGER
CAP. IF STORMS FORM...THE ENVIRONMENT WILL SUPPORT SUPERCELLS
CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS.
...IA/IL/WI/MI/INDIANA THIS AFTERNOON/EVENING...
THE WELL-DEFINED MID LEVEL TROUGH WILL CONTINUE ENEWD FROM ERN IA/SW
WI/NW IL TO SE WI AND LOWER MI THIS AFTERNOON. AN ACCOMPANYING
SURFACE CYCLONE WILL LIKEWISE DEVELOP ENEWD FROM SW WI TO CENTRAL
LOWER MI THROUGH EARLY TONIGHT...AS A WARM FRONT LIFTS NWD INTO SRN
LOWER MI.
SOME INITIAL CONVECTION FARTHER TO THE S IN IL HAS WEAKENED...BUT
THERE WILL BE THE POTENTIAL FOR ADDITIONAL DEVELOPMENT THIS
AFTERNOON FROM NRN INDIANA INTO SRN LOWER MI WHERE WAA PERSISTS ON
THE NE EDGE OF THE RICHER MOISTURE PLUME...AND CLOUD BREAKS ALLOW
SOME LOW-LEVEL DESTABILIZATION. FARTHER W ACROSS NRN IL AND EXTREME
S/SE WI...CLEARING S OF THE WARM FRONT AND IN THE WAKE OF EARLIER
CLOUDS/RAIN WILL ALLOW SUFFICIENT DESTABILIZATION FOR SURFACE-BASED
STORMS TO FORM BY EARLY AFTERNOON. THIS CONVECTION WILL LIKELY BE
FOCUSED IN SHORT BANDS NEAR AND JUST E OF THE SURFACE COLD FRONT AND
SURFACE LOW MOVING OUT OF IA TOWARD NW IL AND SRN WI. LOW-LEVEL
VERTICAL SHEAR WILL BE SOMEWHAT MARGINAL FOR A TORNADO THREAT S OF
THE WARM FRONT...THOUGH SOME SUPERCELL AND EMBEDDED BOW STRUCTURES
MAY PRODUCE A TORNADO OR TWO. OTHERWISE...A FEW DAMAGING WIND AND
LARGE HAIL EVENTS WILL BE POSSIBLE THIS AFTERNOON/EVENING...BEFORE
INSTABILITY DECREASES AND THE SEVERE THREAT WANES NEAR OR JUST AFTER
SUNSET.
...NE CO AREA THIS AFTERNOON/EVENING...
AN UPSLOPE FLOW REGIME IS ESTABLISHED ACROSS NE CO/SE WY IN THE WAKE
OF YESTERDAY/S FRONTAL PASSAGE. THE LARGE SCALE CONTRIBUTION TO
STORM FORMATION WILL BE DIFFUSE TODAY WITH NEUTRAL OR WEAKLY RISING
HEIGHTS...BUT LOCAL TERRAIN CIRCULATIONS AND DAYTIME HEATING WILL
SUPPORT AT LEAST WIDELY SCATTERED THUNDERSTORM DEVELOPMENT. THE
PRESENCE OF A WEAK DENVER CYCLONE AND THE RESULTANT LOW-LEVEL
VORTICITY MIGHT SUPPORT AN ISOLATED TORNADO THIS AFTERNOON...BUT THE
PRIMARY SEVERE THREAT WILL BE LARGE HAIL WITH SUPERCELLS MOVING OFF
THE FRONT RANGE IN AN ENVIRONMENT OF ROUGHLY 1000 J/KG MLCAPE AND
EFFECTIVE BULK SHEAR AOA 40 KT.
...KS LATE TONIGHT...
LOW-LEVEL WAA WILL INCREASE LATE TONIGHT AND MOISTURE/INSTABILITY
SHOULD SPREAD BACK TO THE N WITH THE RETREATING FRONT. THERE IS A
SUFFICIENTLY HIGH PROBABILITY FOR STORMS WITH LARGE HAIL LATE
TONIGHT...THUS WILL INTRODUCE A SLIGHT RISK FOR THE END OF THE
PERIOD.
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