882
WWUS20 KWNS 181711
SEL9
SPC WW 181711
ILZ000-WIZ000-LMZ000-182300-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 599
NWS Storm Prediction Center Norman OK
1210 PM CDT Mon Aug 18 2025

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of
  Northern Illinois
  Southeast Wisconsin
  Lake Michigan

* Effective this Monday afternoon and evening from 1210 PM until
  600 PM CDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible
  A tornado or two possible

SUMMARY...A line of thunderstorms is beginning to develop along an
outflow boundary that extends from far south-central WI into
west-central IL. The airmass ahead of this boundary is very moist
and strongly unstable, supporting the potential for robust updrafts.
Shear is modest, but outflow-dominant storm structures and
water-loaded downdrafts suggest some strong to severe gusts will be
possible throughout the afternoon. Backed low-level flow also
supports a low-probability tornado risk.

The severe thunderstorm watch area is approximately along and 50
statute miles east and west of a line from 30 miles north northwest
of Milwaukee WI to 15 miles southwest of Marseilles IL. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU9).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

AVIATION...A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few
cumulonimbi with maximum tops to 500. Mean storm motion vector
24035.

...Mosier