AREAS AFFECTED...PORTIONS WI...EXTREME NERN IL...LM...SRN UPPER
MI...WRN LOWER MI.
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 271742Z - 272015Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...SVR POTENTIAL MAY INCREASE THROUGH AFTN OVER DISCUSSION
AREA TO EXTENT THAT INITIALLY ISOLATED CONVECTION OVER PARTS OF NRN
AND CENTRAL WI CAN GROW UPSCALE WITH ADDITIONAL DEVELOPMENT
POSSIBLE. MAIN CONCERNS ARE LARGE HAIL AND SPORADIC DAMAGING GUSTS.
DISCUSSION...SFC PATTERN IS RATHER SUBTLE AND FRAGMENTED ACROSS THIS
AREA...WITH POCKETS OF STRONGER VERSUS WEAKER MOISTURE/MIXING AND
HEATING AWAY FROM LM MARINE LAYER. MODEL FCST SOUNDINGS AND
MODIFIED RAOBS SUGGEST AIR MASS ACROSS THIS REGION ESSENTIALLY HAS
LOST MLCINH. SFC DEW POINTS HAVE MIXED DOWN A FEW DEG F DURING LAST
1-2 HOURS FROM PEAK VALUES AT SEVERAL STATIONS IN WI...OFFSET ENOUGH
BY SFC DIABATIC HEATING TO MAINTAIN MLCAPE 1000-2000 J/KG. BUOYANCY
SHOULD REMAIN RELATIVELY MAXIMIZED WITHIN ABOUT 75 NM EITHER SIDE OF
MOISTURE/THETAE AXIS DRAWN FROM SERN IL NNWWD ACROSS S-CENTRAL/WRN
WI. WELL-MIXED SUBCLOUD LAYER WILL SUPPORT DOWNDRAFT ACCELERATION
AS WELL AS MAINTENANCE TO SFC OF ANY SVR HAIL GENERATED ALOFT.
VEERED LOW-LEVEL WINDS WILL LIMIT BOUNDARY-LAYER CONVERGENCE AND
HODOGRAPH SIZE. HOWEVER...DEEP SHEAR IS ENHANCED AROUND SRN RIM OF
MID-UPPER PERTURBATION THAT IS EVIDENT IN MOISTURE CHANNEL IMAGERY
OVER LS. THAT...ALONG WITH BUILDING RIDGE OVER SWRN CONUS...SHOULD
MAINTAIN ENHANCED GRADIENT FLOW ALOFT FOR EFFECTIVE SHEAR MAGNITUDES
RANGING FROM AROUND 60 KT OVER WRN WI TO AROUND 30 KT OVER WRN LM.
..EDWARDS/KERR.. 06/27/2013
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...APX...IWX...GRR...MQT...GRB...LOT...MKX...DLH...
ARX...MPX...
LAT...LON 46069010 45608712 43738543 42388590 41918708 42418906
43989077 45079114 46069010
