843
ACUS11 KWNS 112257
SWOMCD
SPC MCD 112257
ILZ000-WIZ000-120100-

Mesoscale Discussion 1648
NWS Storm Prediction Center Norman OK
0557 PM CDT Fri Jul 11 2025

Areas affected...southern Wisconsin and northern Illinois

Concerning...Tornado Watch 505...508...

Valid 112257Z - 120100Z

The severe weather threat for Tornado Watch 505, 508 continues.

SUMMARY...An organized cluster of storms likely will continue to
pose a risk for strong to severe surface gusts, and perhaps an
additional brief tornado or two, across southern Wisconsin and
northern Illinois during the next couple of hours, reaching the
Greater Milwaukee into portions of the Greater Chicago metro areas
by 8 PM CDT.

DISCUSSION...The evolving convective system has become better
organized over the past couple of hours, with at least one
developing meso-beta scale cyclonic vortex (now near Dubuque IA)
becoming increasingly prominent.  The apex of the southward trailing
bow echo structure in radar reflectivities is propagating
east-northeastward around 45 kt, and, at this continued motion, will
reach the southwestern shores of Lake Michigan near the Greater
Milwaukee area by 01Z.

In the presence of 20-30 kt west-southwesterly mean ambient flow,
moderately strong easterly updraft inflow of seasonably moist air
characterized by CAPE in excess of 1500 J/kg seems likely to
maintain current convective intensities at least to the the
southwestern shores of Lake Michigan.  As long as this continues,
westerly rear inflow probably will remain sufficiently strong to
contribute to strong to severe surface gusts in downdrafts.

..Kerr.. 07/11/2025

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LOT...MKX...DVN...

LAT...LON   43208980 43548869 43568796 43178750 42218756 41788778
            41678926 41768977 42488951 42969002 43208980

MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN