NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 110026
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
726 PM CDT Mon Aug 10 2026

.KEY MESSAGES...

- A few storms may occur this evening along the WI/IL border,
  mainly after 8pm. Isolated gusty winds and hail can't be ruled
  out if a stronger storm occurs. Heavy downpours will also be
  possible.

- Line of strong to severe thunderstorms will be possible across
  southern WI Tuesday mid-morning through the early afternoon,
  which will be capable of producing damaging winds and
  localized flooding.

- Additional periodic chances for showers and thunderstorms are
  possible through the midweek.

- Second half of the week is trending drier with near normal
  temps with a more active pattern returning for the weekend.

&&

.UPDATE...
Issued 715 PM CDT Mon Aug 10 2026

While still cannot completely rule out a few thunderstorms
develop along the nose of the 700-850 WAA later this evening and
overnight, the better forcing remains down across IL/IN
supported by the nose of a building 30 kt LLJ. If any storms
are able to develop along the WI/IL border, there is plenty of
instability to tap into and cannot rule out it producing hail
along with localized flooding. However, the main limiting
factor for this activity will be a forcing mechanism.

Otherwise, looking ahead to the Tuesday morning storm potential.
Models continue to trend toward MCS developing upstream across
the Dakotas/MN tonight and follow a west to east-southeast
thermal and instability gradient. Pair this MCS with PWATs
exceeding 1.5 inches and approaching 2 inches, mid-level
shortwave trough and ripple of vorticity rounding the base of
the broader trough, and ample SBCAPE (+2000 J/KG) and +40 kt of
deep layer shear, and you have the setup for morning/early
afternoon round of storms. Majority of the CAMs align in a line
of strong to severe storms to propagating through just after
daybreak following the general west to east-southeast gradient.
The lingering question is where does this gradient set up.
General consensus is somewhere across our southern CWA around
the WI/IL border, but any wobble could shift the area of concern
in either direction, but for now greater confidence in the
stronger activity is across our southern CWA into northern IL.
The main hazards with this activity will be damaging winds and
heavy rainfall, but could not rule out embedded tornadoes
associated with any bowing structure that may develop within the
line.

Wagner

&&

.SHORT TERM...
Issued 142 PM CDT Mon Aug 10 2026

Tonight through Tuesday night:

Today looks likely to be largely quiet across at least most of
the CWA with the stationary front south of the CWA and WAA and
LLJ focused over northern IL. In addition there does not look to
be much of a shortwave pushing through our CWA today. This
generally appears likely to keep things dry the only
uncertainty associated with this is right along the WI/IL border
where some CAMs are suggestive that afternoon and evening
activity along the front may reach into far southern WI. If
that is the case heavy rain, flooding and even a severe storm
will be possible given high instability and good deep layer
shear. Thus while we cannot rule out flash flooding (PWATS near
1.75-2in), some damaging winds or hail from storms the focus
area wise should be restricted to right along the WI/IL border
in the bottom tier of WI counties. Any storms that may be in WI
should push out by the early overnight hours.

Attention then turns toward Tuesday morning as most models show
a developing MCS overnight in SW MN tracking ESE. This is
currently expected to push through southern WI during the
daylight morning hours. The strength of this is definitely in
question as is the track. The strength is in question primarily
due to the uncertainty in whether the storms will be elevated as
hail isn't expected to be a big concern with damaging winds the
primary concern with these storms. The track is in question
primarily due to the idea that MCSs typically follow the
instability gradient and a WNW to ESE instability gradient we
could see the MCS track a bit more SE that current CAMs suggest.
This would likely have the MCS only impact SW parts of the area.

The severe concerns with this are focused on the damaging wind
aspect given the storm mode (though we cannot rule out hail up
to an inch) but will be impacted by whether these storms are
elevated. If elevated, storms would likely be only borderline
severe at worst but if these storms can become surface based at
any point severe winds would become more likely and we wouldn't
be able to rule out a brief QLCS tornado. The LLJ will likely be
the thing that gets this going and will likely help maintain it
into the morning hours but in order for this to not fall apart
as the LLJ weakens into the day it will have to be strong enough
for its own cold pool to drive it the rest of the way. However,
once these storms blow through by the early afternoon it may
very well leave a quiet day behind it as the front sags further
south and limited forcing and return flow will likely nix
potential for the rest of the day and most of the night though
we could see another shortwave start to push in for Wednesday
morning that may reintroduce chances for at least southwest WI.

Kuroski

&&

.LONG TERM...
Issued 142 PM CDT Mon Aug 10 2026

Wednesday through Monday:

A shortwave trough tracking across the Northern Plains will reach
WI by mid Wednesday morning. A cluster of thunderstorms is
expected with this shortwave, so there is uncertainty about the
track of this area of storms. Will they track straight across
southern WI as they stay tied to the upper jet? Or will they dive
southward with the nose of the LLJ, 850mb frontal boundary, and
the low-level instability gradient? This will depend on how
organized they become upstream during the early Wed morning
hours. The trend is for the storms to split around southern WI,
thus we only have low chances (20 to 35%) of storms.

On Thursday, yet another shortwave is expected to swing across
MN/IA/WI/IL, which will bring another round of storms, mainly
along and south of the WI/IL border. Northeast winds will push all
the way through southern WI by Friday in the wake of a more
prominent shortwave trough that crosses Lake Superior. Friday
highs will be in the mid-upper 70s and cooler along the lakeshore.

The pattern will start shift a little as we get into the weekend.
The mid level high pressure that has been parked over the
southwest and south central states is expected to shift more
toward the southeast states. This would temporarily allow a more
amplified wave and upper jet to cross the Northern Plains/Great
Lakes. In turn, this would help usher the low level jet farther
north toward central WI and bring a chance for stronger storms
to southern WI. The timing of this looks like Saturday night
into Sunday morning. Of course, this is a long way out and
things will change, but the models are starting to latch on to
this idea.

High pressure in the wake of this system should bring a period of
quiet weather for the first half of next week.

Cronce

&&

.AVIATION...
Issued 715 PM CDT Mon Aug 10 2026

VFR conditions will prevail through the remainder of the
evening, but additional chances for fog to develop overnight
into early Tuesday morning will be possible given the light/calm
winds and elevated low-level moisture. This will likely bring
pockets of MVFR visibility and lower ceilings through daybreak.
Then looking at a line of strong to severe thunderstorms to roll
through mid morning through the early afternoon hours. This
activity will not only bring heavy rainfall, lower flight
conditions, and lightning, but also pockets of strong winds.
Main timeframe for this activity will be as early as 10-12z west
of I-39 corridor and linger through 18-20z for area closer to
Lake Michigan. COnditions are then expected to improve behind
this round of activity for Tuesday afternoon with VFR conditions
prevailing through the evening.

Wagner

&&

.MARINE...
Issued 142 PM CDT Mon Aug 10 2026

The stationary front remains over the far southern portion of the
lake with light variable winds are expected into Tuesday as
high pressure around 30.0 inches remains in place north of a
frontal boundary parked over the Corn Belt. Otherwise an
unsettled weather pattern has set up over the Upper Great Lakes
for the start of this week where weak waves of low pressure will
cross the region and produce rounds of thunderstorms at times,
primarily over the southern half of Lake Michigan. A few strong
storm expected over far southern WI tonight and again Tuesday
late morning to early afternoon.

Kuroski

&&

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

$$

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