281
FXUS63 KMKX 181841
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
141 PM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Chance of showers and storms this evening; coverage remains
  uncertain. A few stronger storms with hail and gusty winds are
  possible late afternoon into the evening.

- Dry and pleasant conditions Wednesday through Thursday. Rain
  chances return Friday, but overall nice weather is expected
  for the weekend.

&&

.SHORT TERM...
Issued 141 PM CDT Tue Aug 18 2026

Tonight through Wednesday night:

A largely dry morning with clear skies lingering into the late
morning hours has brought temperatures up a bit across southern
Wisconsin. With breezy southwest winds, WAA is also well
underway with dewpoints slowly rising form the west southwest
to the northeast. The far western edges of the Milwaukee
forecast area are getting dewpoint readings in the upper 60s.
There is a bit of uncertainty in how far east dewpoints in the
upper 60s get, but the longer rain holds off the better the
chances. Higher temps and dewpoints have increased instability
and low level lapse rates across the region. With a cold frontal
boundary expected to move through southern Wisconsin late this
afternoon into this evening, the potential for rain and storms
has increased. So too has the potential for strong to severe
storms. SPC has put a majority of southern Wisconsin in a slight
risk for severe storms (2 out of 5) which is a slight increase
in coverage, duration, and strength of storms compared to
earlier in the day (thanks to the lack of storms this AM).

Meso guidance still overall struggles a bit with the evolution
of storms later this evening. By far every model has storms
developing across central and southern Wisconsin this evening
and slowly moving southeast with the frontal boundary over time.
The one thing that certain models seem to handle poorly are the
storms currently moving east along the WI/IL border. This in
turn just makes a difference in the strength of storms moving
through far southern Wisconsin as the environment gets tapped a
bit in those specific runs. If these storms stay contained to a
small area, then its likely that the environment will remain
primed for additional develop with the cold front. Confidence is
increasing on this scenario with storms expected to percolate
around 3-10 PM. Storm mode is likely to change throughout the
event as effective bulk shear around 30-35 kts across western
positions of the forecast area decrease to around 20-25 kts as
you head east. There could be some supercellular development
where dewpoints and shear is at its best. The straight hodograph
from forecast soundings supports that with the potential for
some larger hail. Therefore, large hail, gusty winds and
lightning are the main concerns. As the storm mode becomes more
linear with time the hail risk is expected to decrease.

Once the front clears this evening into tonight the rain and
thunderstorm chances will fall off. High pressure will then
build in behind the exiting cold front for Wednesday. Dry
weather with light north to northwest winds are expected. Highs
are expected to climb into the lower to upper 70s and a lake
breeze could move inland Wednesday afternoon.

Patterson

&&

.LONG TERM...
Issued 141 PM CDT Tue Aug 18 2026

Thursday through Tuesday:

Higher pressure is expected Thursday ahead of the next system.
High temps will be in the upper 70s/lower 80s with lows in the
60s. Winds will start out light and variable in the early morning
hours, then will shift to be predominately from the west-southwest
while continuing to be light.

The next cold front will move through the region on Friday with
sporadic rain showers expected throughout the morning hours
(20-40% chance). The main front is expected to pass over the CWA
during the afternoon/evening hours with increased PoPs (40-60%
chance). Showers during this time will be more widespread along
the frontal boundary. There is a chance for thunderstorms with
this system as SBCAPE ranges from 1200 J/kg to 3000 J/kg with the
higher SBCAPE amounts near the IA/WI border which is where storms
could be stronger.

After the passage of the cold front, high pressure will build
into the upper Midwest from Canada. Northwesterly winds will be
the predominate condition throughout the weekend which will
advect cooler and drier air from Canada as well. High temps will
top out in the mid to upper 70s inland and be slightly lower along
the shoreline with highs in the lower 70s. RH will be around 50%
each day which will be a nice relief to conditions this past week.

On Monday as the high pressure continues to push eastward, another
low pressure system will begin to push into the region from
Southern Canada/NE MN. Winds will shift to be from the south,
advecting warmer and more moist air from the south which help set
up the next chance for rain/storms. Highs expected in the uppers
70s/low 80s inland and near the mid 70s along Lake Michigan.

A cold front associated with the low pressure system will move
across the CWA on Tuesday. As of right now, timing is expected to
be in the late morning through early afternoon. Amount and
intensity of any precipitation is uncertain at this point.

Soergel/Patterson

&&

.AVIATION...
Issued 141 PM CDT Tue Aug 18 2026

Rain and thunderstorms are expected to move through southern
Wisconsin this afternoon and evening. A few isolated showers
and storms are moving east across the area this afternoon and
should clear out over Lake Michigan in the next hours or so.
Additional storms are expected to develop along a cold front in
portions of central Wisconsin late this afternoon/evening and
move southeast. Storms are expected to be scattered with a few
stronger/severe storms possible. Large hail, gusty winds and
lightning will be the main concerns for any severe storms. Once
the cold front clears this evening rain and storms chances will
end. Breezy southwest winds this afternoon are expected to
become light northwest winds behind the front tonight. Ceilings
are expected to be around 2-4 kft within any of the rain/storms
with visibilities around 2-5 SM.

For the areas that received rain there will be a potential for
low stratus to develop for areas west of Madison during the
early morning hours(ceilings around 500-1500 feet possible with
any stratus). Low stratus should slowly rise and dissipate in
the mid to late morning hours. Light north to northwest winds
will persist through Wednesday evening. A lake breeze is
expected to slowly moving inland which will turn winds to the
east. Light and variable winds with clear skies are expected
Wedensday night.

Patterson

&&

.MARINE...
Issued 141 PM CDT Tue Aug 18 2026

Low pressure moving across the Hudson Bay region today will
drag a cold front southward across Lake Michigan this evening.
Expect prevailing west to southwesterly winds ahead of the cold
front along with a few thunderstorms through this evening. Then
the cold front will push down the Lake by Wednesday bringing a
north-northwesterly winds shift. Winds will weaken and become
more variable as high pressure around 30.0 inches tracks through
the western Great Lakes through Thursday. Southwesterly winds
and thunderstorm chances return later Friday as another system
is progged to bring another cold front across the Upper Great
Lakes region.

Patterson

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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