SWODY1
SPC AC 271954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT MON JUN 27 2011
VALID 272000Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF SRN MO/NRN AR EWD
ACROSS THE TN VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF WI...
...THERE IS A SLGT RISK OF SVR TSTMS OVER NERN/EAST NM INTO WEST
TX...
...THERE IS A SLGT RISK OF SVR TSTMS OVER CENTRAL/ERN NC...
MODIFICATIONS WERE MADE TO THE EARLIER SLIGHT RISK AREA FROM THE
GREAT LAKES INTO THE MID MS VALLEY AND NRN TN VALLEY. SATELLITE
IMAGERY INDICATES APPARENT STABILIZATION HAS OCCURRED IN ASSOCIATION
WITH A SURGE OF WESTERLY LOW LEVEL WINDS IN ADVANCE OF THE COLD
FRONT OVER NRN/CENTRAL IL AND NRN MO...AND THE THREAT FOR ORGANIZED
SEVERE STORMS HAS DIMINISHED ACROSS THIS REGION.
A SLIGHT RISK AREA IS NOW DELINEATED OVER PARTS OF WI AS THE STRONG
UPPER LOW MOVES EWD TOWARD THE UPPER GREAT LAKES...AND STORMS MAY
CONTINUE TO DEVELOP WITHIN AN AXIS OF DESTABILIZATION EXTENDING N/S
THROUGH WI.
A SECOND SLIGHT RISK EXTENDS FROM SRN MO/NRN AR WHERE AIR MASS HAS
RECOVERED IN THE WAKE OF THE MCS NOW MOVING ACROSS KY AND TN. THERE
IS POTENTIAL FOR NEW CONVECTION DEVELOPING OVER SRN MO AS THE COLD
FRONT MOVES INTO THE REGION FROM THE NW...AND STORMS THEN SPREAD EWD
WITHIN A BAND OF STRONGER WESTERLY FLOW ALOFT. FARTHER EAST...RADAR
INDICATES NEW STORMS ARE DEVELOPING ON THE LEADING OUTFLOW OF THE
DOWNSTREAM MCS OVER CENTRAL KY/MIDDLE TN...AND THIS ACTIVITY WILL
HAVE POTENTIAL TO PRODUCE DAMAGING WINDS AND POSSIBLE HAIL.
ELSEWHERE...MINIMAL CHANGES WERE MADE TO THE 1630Z OUTLOOK.
..WEISS.. 06/27/2011
.PREV DISCUSSION... /ISSUED 1128 AM CDT MON JUN 27 2011/
...UPPER GREAT LAKES INTO THE OZARKS AND EWD ACROSS THE OH/TN
VALLEYS...
POTENT VORTICITY MAXIMUM OVER THE UPPER MS VALLEY WILL PROGRESS EWD
THROUGH THE UPPER GREAT LAKES REGION DURING THE D1 PERIOD WITH AN
ATTENDANT BELT OF 40-50 KT MIDLEVEL FLOW MAINTAINED FROM THE CORN
BELT AND OZARKS EWD INTO OH VALLEY. IN THE LOW LEVELS...WIDESPREAD
CONVECTIVE OUTFLOW FROM NOCTURNAL STORM ACTIVITY HAS OBSCURED EXACT
PLACEMENT OF FRONTAL LOCATIONS. HOWEVER...IT DOES APPEAR THAT
PRIMARY SURFACE LOW OVER THE UPPER MS VALLEY WILL DEVELOP EWD INTO
SWRN ONTARIO BY 28/12Z WHILE TRAILING COLD FRONT ADVANCES THROUGH
THE UPPER MIDWEST...MID MS VALLEY AND A LARGE PORTION OF THE OH
VALLEY. MEANWHILE...SURFACE WARM FRONT WILL LIFT NEWD THROUGH THE
GREAT LAKES REGION IN ADVANCE OF MIGRATORY SURFACE LOW.
DECREASING CLOUDS IN THE WAKE OF REMNANT NOCTURNAL MCS NEAR THE
CONFLUENCE OF THE MS/OH VALLEYS WILL ALLOW FOR STRONG DIABATIC
HEATING TO OCCUR AHEAD OF THE COLD FRONT. WHEN COUPLED WITH
BOUNDARY LAYER DEWPOINTS IN THE 60S...EXPECT A MODERATELY TO
STRONGLY UNSTABLE AIR MASS BY AFTERNOON FROM VICINITY OF SURFACE LOW
OVER WI SWD INTO THE OZARKS AND MID MS VALLEY WITH MLCAPE RANGING
FROM 1000-1500 J/KG NORTH TO 2000-3000 J/KG SOUTH. FRONTAL
CONVERGENCE COUPLED WITH INFLUENCE OF GREAT LAKES IMPULSE IS
EXPECTED TO FOSTER SCATTERED STRONG-SEVERE TSTMS ALONG THE COLD
FRONT THIS AFTERNOON WITHIN A KINEMATIC ENVIRONMENT FEATURING 35-50
KT OF DEEP-LAYER SHEAR. THE PRIMARY HAZARDS APPEAR TO BE DAMAGING
WINDS AND LARGE HAIL...THOUGH TORNADOES WILL BE POSSIBLE WITH
SUPERCELLS THAT CAN FAVORABLY INTERACT WITH WARM FRONT OR RESIDUAL
OUTFLOW BOUNDARIES WHERE LOW-LEVEL SHEAR IS ENHANCED.
FARTHER E...MCS APPEARS TO BE RE-INTENSIFYING LATE THIS MORNING OVER
FAR SERN MO/SRN IL. DOWNSTREAM AIR MASS ACROSS THE SRN OH/TN
VALLEYS SHOULD CONTINUE TO DESTABILIZE OWING TO RICH BOUNDARY LAYER
MOISTURE AND DAYTIME HEATING WITH MLCAPE CLIMBING TO 2000-2500 J/KG.
GIVEN 40+ KT WLY FLOW OBSERVED IN THE MIDLEVELS BY VAD/PROFILER
DATA...SETUP APPEARS FAVORABLE FOR THE CONTINUED EWD PROGRESSION OF
SYSTEM WITH THE POTENTIAL FOR DAMAGING WINDS AND HAIL.
ELSEWHERE...ADDITIONAL STRONG-SEVERE STORMS WILL BE POSSIBLE ALONG
RESIDUAL OUTFLOW BOUNDARIES AND WARM FRONT LIFTING THROUGH LOWER MI
AND THE MID/UPPER OH VALLEY. THOUGH INSTABILITY WILL BE
COMPARATIVELY WEAKER THAN POINTS TO THE W...SUFFICIENT
DESTABILIZATION IS EXPECTED TO SUPPORT ORGANIZED STORM
MODES...INCLUDING MULTICELLS...MARGINAL SUPERCELLS AND BOWING
STRUCTURES. HERE TOO...DAMAGING WINDS AND HAIL WILL BE THE MAIN
THREATS THOUGH A TORNADO OR TWO ARE POSSIBLE.
...SRN HIGH PLAINS...
POST-FRONTAL LOW-LEVEL WIND FIELD WILL VEER TO MORE OF AN ELY/SELY
DIRECTION LATER TODAY AS SURFACE ANTICYCLONE BUILDS FROM THE NRN
HIGH PLAINS TO THE NRN/CNTRL PLAINS. THIS WILL MAINTAIN A FEED OF
50+ F DEWPOINTS INTO THE HIGH TERRAIN BENEATH EML PLUME...RESULTING
IN AFTERNOON MLCAPE OF 1000-1500 J/KG. THOUGH MIDLEVEL HEIGHT FIELD
MAY REBOUND SLIGHTLY WITH THE PASSAGE OF THE N-CNTRL CONUS SYSTEM TO
THE NE...STRONG HEATING ALONG THE HIGH TERRAIN AND LOW-LEVEL UPSLOPE
FLOW MAY BE SUFFICIENT TO FOSTER ISOLATED STORMS WITHIN A KINEMATIC
ENVIRONMENT CHARACTERIZED BY 35-40 KT OF DEEP WLY SHEAR. THIS SETUP
WILL SUPPORT SUPERCELL STORM MODES WITH A RISK FOR MAINLY LARGE HAIL
THROUGH THIS EVENING.
...SERN ATLANTIC COAST...
SCATTERED-NUMEROUS TSTMS ARE EXPECTED TO DEVELOP TODAY ALONG
RESIDUAL OUTFLOW BOUNDARIES AND DEVELOPING SEA BREEZE CIRCULATION
WITHIN A HIGH PW AIR MASS WHERE MLCAPE VALUES WILL APPROACH
2000-3000 J/KG. CURRENT INDICATIONS ARE THAT THE MOST CONCENTRATED
AREA FOR TSTM DEVELOPMENT AND GREATEST POTENTIAL FOR DAMAGING WET
MICROBURTS WILL BE NEAR THE NEXUS OF THE STALLED SYNOPTIC FRONT AND
PRE-FRONTAL TROUGH ACROSS ERN NC THIS AFTERNOON INTO EVENING.
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