NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 161148
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
648 AM CDT Sun Aug 16 2026

.KEY MESSAGES...

- Isolated showers and even a rumble of thunder cannot be ruled
  out into the afternoon, but it will be predominately dry
  today.

- Drier and seasonal Monday with storm chances returning
  Tuesday into Wednesday.

&&

.UPDATE...
Issued 650 AM CDT Sun Aug 16 2026

Lingering patchy fog this morning will lift, but clouds remain
through the morning. A cold front will work its way through the
area today and cannot rule out a few isolated showers and even
a storm or two along it through the afternoon. However, much of
the area will remain dry today. High pressure will build in for
Monday with drier conditions.

Wagner

&&

.SHORT TERM...
Issued 1027 AM CDT Sat Aug 15 2026

Today and Tonight:

A few isolated showers and storms will be possible predominately
along Wisconsin/Illinois border. Can't rule out a stray shower
making its way to the Interstate 94 corridor but the majority
of the precipitation should stay along the state border. These
showers and storms are being driven by an upper level short wave
and sfc cold front. Despite being warm, having good moisture
and occasionally afternoon diurnally driven instability, all the
rain/storms are being heavily driven by the PVA aloft. Tonight
should follow that pattern as well. With shortwave and PVA just
to our south the major of the rain and all the stronger storms
should remain in Illinois. What instability we got this
afternoon will be falling now that the sun has set. Lapse rates
are low and bulk shear is awful so if we get any storms,
lightning will be the main concern. Infrequent lightning at
that.

While the sfc cold front will kick off some of the rain and
storms, this is expected to lag behind the upper level short
wave a bit. The weak sfc convergence with diurnally driven
instability and lingering mid level moisture could be just
enough to get additional rain and storm develop Sunday
afternoon. Chances for this are low around 10-30% and any rain
that does develop is expected to be scattered. Lakeshore
counties will have the best chances for this rain, while inland
areas are expected to largely stay dry. Once the sunsets or the
cold front pulls east these shower chances will end quickly.
Sunday evening and overnight hours are expected to be dry.

Patterson

&&

.LONG TERM...
Issued 1027 AM CDT Sat Aug 15 2026

Sunday through Friday:

Heading into Monday morning high pressure is expected to slowly
move across the southwestern Great Lakes Region. This broad area
of high pressure in the northern plains is expected to slow move
toward the mid Atlantic by Tuesday bringing a brief period of
subsidence to the state. Thus dry weather and generally quiet
conditions are expected Monday.

Rain chances are expected to return Tuesday into Wednesday as
another cold front moves across Wisconsin. Moisture will need to
return behind the exiting high pressure to help any rain even
develop.There could be a world where dry air erodes at some of
the storms or prevents stronger storms from developing unless
WAA out ahead of the cold front is robust. Global ensembles
generally put southern Wisconsin on the northern edge of this
instability and moisture. An upper level trough is expected to
swing through Canada and the Great Lakes Region during this
time as well which will provide a nice period of lift and maybe
some influence of the upper level jet. If all of these
ingredients can come together at the right time and in the right
place then there could be some stronger storms and heavy rain.
The best timing of rain and storms looks to hold off until
Tuesday evening into Tuesday night. This current run of guidance
has come in slightly drier and lower POP chances, however, this
seems to be a trend over the last couple of days. 12Z guidance
being generally wetter than 00Z guidance. Which has created this
osculating pattern from update to update. For this reason,
there stuck to the average of guidance and kept a healthy sense
of skepticism.

As we start to enter into a more meridional flow aloft, high
pressure is expected to return Thursday. This area of high
pressure will bring a brief period of dry weather as the high
swings from the Northern Plains through the Great Lakes and
into the New England States. Beyond this low chances (~20%) for
rain chances look to return for the weekend. There is a lot of
uncertainty here as guidance have varying tracks and strengths
of an upper level trough. Its fairly easy to see these
differences in the deterministic runs, but this is also visible
in ensembles and cluster analysis. Regardless of rain chances,
temperatures look to be fairly consistent through the extended
with highs ranging in the mid 70s to low 80s for much of
southern Wisconsin.

Patterson

&&

.AVIATION...
Issued 650 AM CDT Sun Aug 16 2026

A mix of MVFR to LIFR ceilings remain in place through the
morning while the patchy fog continues to lift and improve
visibilities. Otherwise, looking at south to westerly winds
ahead of the approaching cold front. While much of the area is
expected to remain dry, could see a few isolated shower and
maybe a rumble of thunder across southern WI through the
afternoon. However, potential remains low to leave out of
current TAFs. Ceilings lift and improve with the cold front
passage today and will see a northwesterly wind shift. Expect
light northerly winds overnight as high pressure builds into the
area for Monday.

Wagner

&&

.MARINE...
Issued 1027 AM CDT Sat Aug 15 2026

Low pressure around 29.9 inches in Manitoba will move northeast
toward James Bay tonight into Sunday morning. An associated cold
front is expected to move across the lake Sunday. Southeast winds
out ahead of the front will turn to northwesterly and become
breezy behind the front. Periods of scattered showers and
thunderstorms will be possible along and ahead of the front
tonight through Sunday morning. Severe weather is not
anticipated.

A new area of 30.1 inch high pressure will build in from the
northern Great Plains late Sunday night into Monday, bringing
light and variable winds to the waters through the majority of
Monday and Monday evening. A slow-moving cold front will approach
from the northern Great Plains Tuesday into Wednesday, bringing
increasing southwest winds and chances for thunderstorms. Precise
timing details will continue to be refined over coming forecasts,
though it does appear that a few stronger storms could be possible
over the southern half of the waters Tuesday afternoon & night.
Winds will trend light and variable behind the front from
Wednesday night through the end of next week.

Patterson

&&

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

$$

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