ZCZC SPCSWOMCD ALL
ACUS11 KWNS 191803 
SPC MCD 191803 
MIZ000-OHZ000-INZ000-ILZ000-191900-

MESOSCALE DISCUSSION 1580
NWS STORM PREDICTION CENTER NORMAN OK
0103 PM CDT TUE AUG 19 2014

AREAS AFFECTED...SOUTHERN LOWER MI...NORTHERN/CENTRAL IND...PART OF
EASTERN IL AND NORTHWEST OH

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 191803Z - 191900Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...WW ISSUANCE IS POSSIBLE THIS AFTERNOON ACROSS PORTIONS OF
SRN LOWER MI SSWWD THROUGH NRN/CENTRAL IND...NWRN OH...TO
EAST-CENTRAL IL.  GREATEST SEVERE RISKS WILL BE DAMAGING WINDS AND
LARGE HAIL.

DISCUSSION...TRENDS IN MOSAIC RADAR IMAGERY AND LIGHTNING DATA
INDICATED AN INCREASE IN TSTM DEVELOPMENT FROM CENTRAL AND SWRN
LOWER MI THROUGH SRN LAKE MICHIGAN TO NERN IL /INCLUDING THE CHICAGO
METRO AREA/...WITH ISOLATED DEVELOPMENT IN EAST CENTRAL IL.  THIS
ACTIVITY HAS FORMED EAST OF A COLD FRONT...WHICH AT 17Z EXTENDED
FROM NRN/CENTRAL LAKE MICHIGAN SWWD THROUGH NRN IL TO NRN MO...AND
ALONG A DIFFERENTIAL HEATING BOUNDARY.  THE MESOSCALE-LINEAR
STRUCTURE OF THESE STORMS IS LIKELY ATTENDANT TO THE ORIENTATION OF
THE DIFFERENTIAL HEATING BOUNDARY AND THE LEADING EXTENT OF DEEP
LAYER ASCENT SPREADING E/SEWD ACROSS THIS REGION WITH THE
APPROACHING UPPER TROUGH.

ADDITIONAL SURFACE HEATING ACROSS THE DISCUSSION AREA /EAST OF THE
DEVELOPING STORMS/...WITHIN A MOIST ENVIRONMENT /PW EXCEEDING 1.5
INCHES AND SURFACE DEW POINTS IN THE UPPER 60S TO AROUND 70 F/...IS
EXPECTED TO SUPPORT A FURTHER INCREASE IN STORM DEVELOPMENT/
INTENSITY.  EFFECTIVE BULK SHEAR OF 25-30 KT WILL SUPPORT MULTICELL
STORMS.  STORM MERGERS RESULTING IN A CONGLOMERATE OF COLD POOLS
COULD ENHANCE THE THREAT FOR STRONGER/DAMAGING WIND GUSTS AS
ACTIVITY ADVANCES INTO AN UNSTABLE ENVIRONMENT.  HAIL WILL ALSO BE A
THREAT.  TRENDS WILL CONTINUE TO BE MONITORED FOR POTENTIAL WW
ISSUANCE FROM PARTS OF SRN LOWER MI THROUGH NRN/CENTRAL IND TO
EAST-CENTRAL IL.

..PETERS/THOMPSON.. 08/19/2014

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

ATTN...WFO...DTX...IWX...GRR...IND...LOT...ILX...

LAT...LON   40308831 40818791 41408715 42378565 43188369 42918323
            42468325 40758492 39848625 39628767 39788841 40308831 

NNNN