780
FXUS63 KMKX 170839
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
339 AM CDT Tue Jun 17 2025

.KEY MESSAGES...

- Chances for showers and thunderstorms at times through the
  rest of the week, with the better chances for stronger storms
  this afternoon into Wednesday night.

- Very warm and humid conditions are looking more likely for the
  weekend into early next week.

&&

.SHORT TERM...
Issued 300 AM CDT Tue Jun 17 2025

Today and Tonight:

A cold front based from the low pressure system moving across
the northern Great lakes will continue through the region early
this morning but will for the most part remain dry outside of a
few isolated showers. This front will layover and become
stationary and east-west oriented as it becomes the warm front
for the developing system over the Central Plains that will be
push east toward the area today.

There still remains quite a bit of uncertainty on where this
boundary will end up as it will be the focus for convection
later today. In addition to the front there will some upper
level support from a shortwave as well with some WAA to the low
to midlevels on the nose of a weak LLJ. In addition moisture is
not really expected to be an issue so this largely comes down to
location of where things get going and models still show quite
a bit of differences. Most of the CAMs show convection across at
least parts of the area but the RRFS and HRRR keep most of the
potential south of the area. We will need to closely monitor
where the front sets up later today to determine where the best
chances for storms will be. In either case while instability may
be plentiful the deep layer shear will be weak and thus storms
may not organize all that well. Depending on where the boundary
sets up we could see upwards of 2000 J/kg of MUCAPE and thus we
couldn`t rule out stronger storms but that shear environment
would not likely sustain them for very long. Large hail would be
the primary concern with storms with a chance for stronger gusts
as well, especially with any degree of organization.

Best chances for storms will be during the late afternoon
through the mid evening hours with quieting conditions overnight
ahead of the approaching low into Wednesday morning.

It is worth mentioning that temperatures will likely reach the
mid 80s with temperatures possible reaching the 90s east of the
Kettle Moraine in southeast WI with help from downsloping with
west to southwest winds. In addition we could see dewpoints in
some spots get near 70 making for some humid conditions. A lake
breeze circulation may also form later in the day despite modest
west winds as the temperature differences will be quite stark
perhaps strengthening the circulation more than models currently
project.

Kuroski

&&

.LONG TERM...
Issued 300 AM CDT Tue Jun 17 2025

Wednesday through Monday:

Synopsis:
Surface low pressure approaches from the central Great Plains and
crosses our region on Wednesday, bringing additional chances for
showers and thunderstorms, with a risk (level 1 or 2 out of 5)
for strong to severe storms and a marginal risk (level 1 out of 4)
for excessive rainfall. The strong / severe storm risk is
conditional, and will depend on the exact track of the low
pressure system, which is widely disputed among model guidance.

There is a chance for showers and thunderstorms to redevelop
Thursday, wrapping around the back side of the departing low
pressure. A deeper low pressure developing over the northern
Plains will drag a warm front northward across the region on
Friday yielding slight chances for showers and thunderstorms.
Behind the warm front, this weekend is looking very warm, with
inland highs around 90 in the forecast and a modest southwest wind
minimizing or even erasing the lake breeze.

Wednesday`s Conditional Storm Threat / Analysis:
The positioning and magnitude of CAPE varies widely from one
ensemble member to the next, largely dependent on whether the low
pressure system passes slightly north or slightly south of us. A
track just south of the region (northern IL) would allow
northeasterly winds off Lake Michigan to limit instability,
whereas a central WI track would pull the warm sector deep into
our region.

Ensemble and deterministic 500mb plots have a similar disagreement
on upper-level dynamics and whether or not shear will be
supportive of storm organization. A jet streak is expected east
of a shortwave trough somewhere nearby, and it`s proximity will
dictate the amount of southwesterly deep shear we will receive.
Ensemble mean plots center this jet streak over northern IL /
southern Lake Michigan / lower Michigan, with over 45 kt of
southwesterly flow (likely much faster in reality, given the
dispersion of model members).

Sheppard

&&

.AVIATION...
Issued 300 AM CDT Tue Jun 17 2025

Thunderstorms are possible later this afternoon into the mid
evening, especially for terminals across the southern portion of
the area. Winds through the period modest from the west today.
Through the day today scattered to broken VFR CIGS are expected.
However overnight into Wednesday we will likely see MVFR CIGS
push in with the low pressure system sliding in.

Kuroski

&&

.MARINE...
Issued 300 AM CDT Tue Jun 17 2025

Low pressure will cross Lake Superior early this morning, and
high pressure will settle into the Upper Midwest on today. Low
pressure will cross eastern Iowa Wednesday morning and reach
central Lower Michigan by Wednesday evening while strengthening.
High pressure will set up over the Plains Thursday, with the
top of the ridge over Lake Superior and northern Lake Michigan.

Expect breezy southerly winds early this morning with highest
gusts over the north half of Lake Michigan. Winds will become
lighter and shift west later today. Lighter and variable
conditions will return Wednesday, then become westerly Thursday.
While showers and thunderstorms are possible through much of the
week, the time period with the best chance for storms is later
this evening through Thursday morning.

Kuroski

&&

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

$$

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