MESO: Mesoscale Discussion 0849

ACUS11 KWNS 201553
SWOMCD
SPC MCD 201552
MIZ000-WIZ000-201745-

MESOSCALE DISCUSSION 0849
NWS STORM PREDICTION CENTER NORMAN OK
1052 AM CDT SUN MAY 20 2012

AREAS AFFECTED...CNTRL AND NRN WI THROUGH THE WRN UPPER PENINSULA OF
MI

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 201552Z - 201745Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...STORMS DEVELOPING ALONG AND JUST AHEAD OF THE COLD FRONT
SHOULD UNDERGO A GRADUAL INCREASE IN COVERAGE AND INTENSITY
INITIALLY FROM WRN THROUGH W CNTRL WI AND NWD INTO THE WRN UPPER
PENINSULA OF MI. DEVELOPING STORMS WILL EVENTUALLY POSE A THREAT OF
MAINLY DAMAGING WIND AND ISOLATED LARGE HAIL...BUT A COUPLE OF
TORNADOES CANNOT BE RULED OUT. A SEVERE THUNDERSTORM WATCH WILL
LIKELY BE NEEDED BY 17Z-18Z.

DISCUSSION...LATE THIS MORNING A COLD FRONT EXTENDS FROM LAKE
SUPERIOR SWWD TO A SURFACE LOW NEAR THE WI/MN BORDER THEN SWD
THROUGH SERN MN AND ERN IA. BOUNDARY LAYER DESTABILIZATION IS
OCCURRING IN THE PRE-FRONTAL WARM SECTOR WHERE UPPER 50S TO 60F
DEWPOINTS EXIST BENEATH 7-7.5 C/KM MID LEVEL LAPSE RATES. OBJECTIVE
ANALYSIS ALREADY SHOWS MLCAPE RANGING FROM 1000-1500 J/KG OVER MUCH
OF WI. STORMS CURRENTLY DEVELOPING WITHIN ZONE OF PRE-FRONTAL
CONFLUENCE AND ISENTROPIC ASCENT IN NWRN WI ARE AT LEAST SLIGHTLY
ELEVATED AND MAY POSE A NEAR TERM RISK FOR MARGINALLY SEVERE HAIL.

MODIFIED 12Z RAOBS SUGGEST SURFACE BASED CONVECTIVE INHIBITION WILL
WEAKEN SIGNIFICANTLY ONCE SURFACE TEMPERATURES REACH THE MID 80S.
ADDITIONAL STORMS WILL LIKELY DEVELOP AS PROGRESSIVE SHORTWAVE
TROUGH AUGMENTS DEEP ASCENT ALONG ADVANCING COLD FRONT. VERTICAL
SHEAR FROM 35-40 KT IN VICINITY OF BAROCLINIC ZONE WILL SUPPORT
ORGANIZED STORMS INCLUDING EMBEDDED SUPERCELL AND LEWP STRUCTURES.

..DIAL/WEISS.. 05/20/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MQT...GRB...MKX...DLH...ARX...MPX...

LAT...LON 46468754 43888873 43409113 45109113 46858883 46468754

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