990
FXUS63 KMKX 261451
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
951 AM CDT Sat Jul 26 2025

.KEY MESSAGES...

- Scattered to areas of showers with an isolated thunderstorm or
  two through early afternoon. Locally heavy rainfall is
  possible, especially south of I-94.

- Fog is expected to develop tonight with areas of dense fog
  (visibility less than a quarter mile) possible.

- Hot and very humid Sunday and Monday with upper 90s to triple
  digits heat indices.

- Periodic shower/storm chances through later Sunday and into
  early next week before an eventual cold front passage midweek.

&&

.UPDATE...
Issued 943 AM CDT Sat Jul 26 2025

A MCS is tracking south of the area across central IL, but we
are seeing showers and a few thunderstorms develop on the
northern fringes along the lifting frontal boundary. Expecting
this activity to continue through the remainder of the morning
with the more moderate to heavy rainfall along and south of
I-94 to the WI/IL where the higher PWATs around 2 inches and the
instability gradient exists. Latest radar trends are showing a
northeastward expansion of the showers as the frontal boundary
lift northward and generally will extend up toward HWY-151, but
areas northwest are likely to remain mostly dry being too far
removed from the MCS and forcing. Otherwise, will see the shower
and isolated storm potential work it way across southern WI
into the early afternoon. As the MCS tracks into IN will begin
to see shower/storm chances diminish from the northwest to
southeast through the afternoon.

Overall rainfall amounts north of I-94 should remain below a
quarter of an inch while areas south of I-94 should generally
be around and below half an inch. However, locally higher
amounts approaching or even exceeding an inch will be possible
for areas south toward the WI/IL given the tropical type
environment and moderate/heavy showers moving over the same
area. While cannot rule out localized minor flooding in low-
lying and urban areas, much of the moderate/heavy showers are
fairly progressive and not sitting in one spot for too long. But
will continue to monitor trends as the activity is tracking
parallel along the lifting frontal boundary through the
remainder of the morning into the early afternoon.

Wagner

&&

.SHORT TERM...
Issued 308 AM CDT Sat Jul 26 2025

Today and Tonight:

Showers and a few occasional thunderstorms continue to percolate
across southern Wisconsin early this morning, as a series of
weak vort maxima rotate east across a weak baroclinic zone. This
front will gradually lift northward today, with increasing
chances of rain through mid day. Rain chances will then end from
west to east this afternoon as the upper level lift shifts east
of the area.

The primary threat from convection today will be heavy rain,
given storm motions parallel to the boundary and a tropical
airmass in place. Prolonged periods of heavy rain, especially
over any developed/urban areas, will pose a threat for flooding.

Temperatures today will be warmest across the western third of
the forecast area, where precipitation and cloud cover will not
be as widespread. Highs in the mid to upper 80s are expected
across this area, with low 80s farther to the east.

No precipitation is expected tonight, but a combination of
clearing skies, rich low level moisture, and light and variable
winds will be favorable for fog development.

Boxell

&&

.LONG TERM...
Issued 308 AM CDT Sat Jul 26 2025

Sunday through Friday:

Upper level ridging builds in for the second half of the weekend
on into early next week which again features some hot and humid
conditions across southern Wisconsin. Starting on Sunday, strong
southerly low level flow will set up across the Upper Mississippi
River Valley which will bring some of the higher surface dew
points back into the mid 70s. With temperatures reaching around
90F on Sunday, heat indices will be pushing 100F in some spots and
we may need a Heat Advisory depending on how cloud cover plays
out.

Sunday night into Monday morning appears to be a challenge MCS
forecast-wise. An extremely unstable air mass sets up across MN on
Sunday with the nose of a low level jet/925-850mb moisture
transport pushes up into central MN. The 26.00z NAM and 25.18z
GFS/ECMWF all show a line of storms developing NW of the Twin
Cities and then diving almost straight south-southeastward along
the instability gradient, which appears to go into WI. The GFS is
further NE and would be more of an issue for southern WI toward
early morning. Theres`s a lot of questions at the moment for where
it would be more likely to, but there at least is consensus that
something will develop and track southward. What happens with this
feature on Monday morning will affect how warm things will get and
the potential is there for another advisory/warning situation.

Going toward midweek, the trend continues to favor a transition to
NW flow aloft, which will usher in much cooler temperatures for
the end of the week. The question is...when will that transition
occur with the front getting shunted south. The frontal boundary
appears to get hung up across southern WI going into Tuesday
before there`s a push southward Tuesday night into Wednesday
morning which should end the hot/humid conditions along with the
potential for being in the MCS train. As is typical with this type
of pattern, there`s a bunch of uncertainty and will have to go day
by day to nail down the specifics.

Halbach

&&

.AVIATION...
Issued 943 AM CDT Sat Jul 26 2025

Frontal boundary continues to lift northward across southern WI
this morning bringing lower IFR/MVFR ceilings along with
showers and a few embedded thunderstorms. Expecting these lower
flight conditions to continue through the remainder of the
morning and gradually improve from west to east through the
afternoon with light southerly winds. Given the light winds and
ample low-level moisture, expecting widespread fog to develop
across the area tonight. Areas of dense fog (visibility less
than a quarter of a mile) possible, especially for areas closer
to the WI/IL where they received the rainfall this morning.
Lower flight conditions expected to persist into Sunday morning
before improving as things warm up.

Wagner

&&

.MARINE...
Issued 308 AM CDT Sat Jul 26 2025

A stalled frontal boundary will gradually lift north across
Lake Michigan today. Will see lighter north and easterly winds
north of the boundary, but will begin to shift more southerly
behind it. Light southerly winds will prevail by this
afternoon/evening across all of Lake Michigan. Will continue to
see light to occasionally moderate southerly winds prevail
through the weekend into early next week. There will be a few
windows for shower and thunderstorms to track across the Lake
tonight/Saturday and again Sunday night into Monday and again
midweek. May see more variable winds accompanying any storm
complex that traverses the Lake through early next week.

Boxell

&&

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

$$

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