SWODY1
SPC AC 201958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT MON JUN 20 2011
VALID 202000Z - 211200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER CENTRAL/ERN NEB...SERN
SD...WRN IA...NWRN MO...ERN KS AND OK...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL/SRN PLAINS
INTO THE OH VALLEY AND SOUTHEASTWARD INTO THE CAROLINAS...
...CENTRAL/SRN PLAINS...
TORNADIC SUPERCELL OVER NRN NORTON CNTY KS IS MOVING NEWD IN CLOSE
PROXIMITY TO DEEP SURFACE LOW NEARING THE KS/NEB BORDER.
18Z SPECIAL SOUNDINGS AT OAX/TOP/LMN/OUN EXHIBIT A CAPPING INVERSION
BASED BETWEEN 800-700 MB. THE CAP IS EXPECTED TO GRADUALLY WEAKEN
AS LARGE SCALE ASCENT ASSOCIATED WITH THE UPPER LOW LIFTING NEWD
OVER THE CENTRAL PLAINS AND LOW LEVEL CONVERGENCE ALONG DRY LINE AND
ADVANCING COLD FRONT INCREASE THIS AFTERNOON AND EVENING. LATEST
HIGH RESOLUTION MODEL GUIDANCE INDICATES SEVERE STORMS SHOULD
DEVELOP FROM PARTS OF CENTRAL/ERN NEB SWD INTO SRN OK AND POSSIBLY
NRN TX. STEEP LAPSE RATES ABOVE THE INVERSION...STRONG VERTICAL
SHEAR AND LARGE INSTABILITY FAVOR POTENTIAL FOR VERY LARGE
HAIL...DAMAGING WIND GUSTS AND A FEW TORNADOES. THE MOST LIKELY
AREA FOR STRONG TORNADOES WILL BE OVER CENTRAL/ERN NEB WHERE BACKED
LOW LEVEL WINDS ARE ENHANCING LOW LEVEL SHEAR/SRH...AND THE MODERATE
RISK AREA HAS BEEN EXPANDED TO REFLECT THIS ASSESSMENT.
OTHERWISE...NO CHANGES HAVE BEEN MADE TO PREVIOUS OUTLOOK.
..WEISS.. 06/20/2011
.PREV DISCUSSION... /ISSUED 1103 AM CDT MON JUN 20 2011/
...CENTRAL/SRN PLAINS...
UNSEASONABLY STRONG UPPER LOW MOVING FROM CURRENT POSITION SE CO
NEWD ACROSS WRN KS INTO SRN NEB BY 12Z TUE. 60-70KT 500MB JET MAX
WITH ASSOCIATED STRONG ASCENT/DIVERGENCE SPREADING NEWD FROM CENTRAL
HIGH PLAINS ACROSS KS INTO NEB THIS AFTERNOON. SURFACE LOW OVER
W-CENTRAL KS WILL MOVE SLOWLY NNEWD INTO SRN NEB. THE DRY LINE
EXTENDING FROM THE LOW SWD THRU FAR WRN OK/SWRN TX WILL SHIFT EWD BY
MID AFTERNOON TO EXTEND ON A N/S AXIS VICINITY THE I-35 CORRIDOR.
VERY STRONG SLY WINDS AHEAD OF DRY LINE WILL WRAP NWWD THE MOIST AND
UNSTABLE AIR MASS TO N OF SURFACE LOW INTO CENTRAL NEB.
THE STRONG LARGE SCALE ASCENT COUPLED WITH THE POST FRONTAL MOIST
NLY FLOW WRN KS THIS AM HAS GENERATED ELEVATED SEVERE THUNDERSTORMS.
BY MID AFTERNOON CONDITIONS WILL RAPIDLY DEVELOP TO SUPPORT AN
OUTBREAK OF SEVERE THUNDERSTORMS BOTH ALONG THE DRY LINE AND IN THE
VERY FAVORABLE SHEAR AND LARGE SCALE ASCENT REGION TO THE N/NE OF
THE SURFACE LOW ACROSS NEB.
THE STRONGLY SHEARED PROFILES AHEAD OF THE SURFACE LOW OVER ERN NEB
COUPLED WITH MLCAPES CLIMBING TO AOA 2000 J/KG EXPECTED TO SUPPORT
TORNADIC SUPERCELL DEVELOPMENT BY MID/LATE AFTERNOON. THERE IS THE
POTENTIAL OF STRONG TORNADOES GIVEN THE ENVIRONMENT THAT WILL BE IN
PLACE.
DOWN THE DRY LINE SCATTERED SUPERCELLS WILL DEVELOP AS THE CAP
BREAKS BY MID/LATE AFTERNOON. BY THAT TIME MLCAPES WILL HAVE CLIMBED
TO AOA 2500 J/KG SWD TO THE OK/TX BORDER WHICH WHEN COUPLED WITH THE
PRESENCE OF THE MID LEVEL JET MAX AND VERY STEEP LAPSE RATES WILL
RESULT IN A VERY LARGE HAIL POTENTIAL ALONG WITH DAMAGING DOWNBURST
WINDS. IT NOW APPEARS COVERAGE OF BOTH THE HAIL AND WIND WILL BE
SUFFICIENT TO UPGRADE THE RISK TO MDT AS FAR S AS THE OKC AREA .
THERE WILL ALSO BE THE POTENTIAL FOR TORNADOES GIVEN THE 50-60 KT OF
SHEAR. FURTHER S INTO NCENTRAL TX THE EXPECTED COVERAGE WILL BE
LESS BUT THERE IS STILL POTENTIAL OF VERY LARGE HAIL AND DAMAGING
DOWNBURSTS.
UPSCALE ORGANIZATION OF ONE OR MORE CLUSTERS IS ONCE AGAIN POSSIBLE
TONIGHT WITH THE RISK OF WIDESPREAD DAMAGING WINDS AS STORMS SPREAD
INTO IA/MO.
...OH VALLEY TO CAROLINAS...
A BAND OF MODERATELY STRONG MID LEVEL WINDS EXTENDS FROM IND/OH INTO
THE CAROLINAS TODAY. THE PRIMARY LOW LEVEL INSTABILITY GRADIENT
WILL ALSO RUN ALONG THIS CORRIDOR. MULTIPLE CLUSTERS OF STRONG TO
SEVERE THUNDERSTORMS ARE LIKELY OVER THIS REGION THIS AFTERNOON AND
TONIGHT. DAMAGING WINDS WOULD BE THE MAIN THREAT ASSOCIATED WITH
BOWING SEGMENTS...ALTHOUGH THE STRONGEST STORMS COULD ALSO PRODUCE
LARGE HAIL.
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