NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 042350 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
650 PM CDT Sat Jul 4 2026

.KEY MESSAGES...

- Brief funnel clouds remain possible over far southwest
  Wisconsin through 8 PM.

- Areas of dense fog along the Lake Michigan lakeshore. Patchy
  fog expected for inland areas overnight.

- Scattered showers and thunderstorms through early evening,
  especially across southwestern WI. A strong storm or two with
  wind gusts to 40mph and cloud to ground lightning are the main
  hazards expected.

- A seasonably warm, comfortable airmass will enter the area the
  first few days of next week.

&&

.UPDATE...
Issued 650 PM CDT Sat Jul 4 2026

Scattered showers and storms continue to percolate across
southwestern WI, with a rogue cell working its way southwest
from southeastern Columbia County into northeastern Dane County
over the next hour. There is still an opportunity for a funnel
or two with the activity over southwestern WI, though this risk
will diminish after 8 PM. Otherwise, cloud to ground lighting
and heavy downpours are the main concerns.

Much, if not all shower/storm activity should exit to the south
after 10am, though will continue to mention low PoPs for the
occasional rogue shower or two developing into the overnight
hours.

Given recent rain, light winds, a continued moist airmass and a
little smoke from area fireworks, have included patchy fog
wording into the forecast into the overnight hours.

The forecast for Sunday is still a bit uncertain as recent CAM
trends indicate an increased chance for showers and perhaps a
few storms over southeastern WI during the morning hours. Will
examine the 00z guidance and alter rain chances accordingly.

Gagan

&&

.SHORT TERM...
Issued 220 PM CDT Sat Jul 4 2026

Rest of Today and Sunday:

A boundary with surface convergence developed from northwest
Iowa to south central WI. There are showers and thunderstorms
that are developing along this east-west boundary (northern Dane
County to south half of Dodge County). Before the showers
develop, funnel clouds seem to be present. We have had several
reports of funnel clouds. We have enough low level instability
(SPC mesoanalysis identifying this axis with the non-supercell
tornado parameter) to support these funnels so for now we will
handle these like landspouts with SPSs. These are brief and weak
and we cannot pick up the rotation on radar. Once the rain
develops, it wipes out the funnel. There are signs of outflow
from these storms, so that should diminish funnel chances. We
are also seeing an inland progression of the lake breeze, so
that will help cut off our chances for funnels.

Dense fog developed over the open lake and expanded to the
nearshore areas from Sheboygan to Kenosha. Models picked up on
this to some degree and most gradually shift the axis of dense
fog southward down the lake through early evening. While this is
a viable option, the forecast winds remain persistent in an
onshore/northeast direction through tonight, then increase
Sunday morning. I was not confident enough that the fog would
actually move offshore or diminish with the winds in that
direction, so I have a Marine Dense Fog Advisory for most of
Lake Michigan, including the Nearshore areas, in effect until
10AM Sunday.

An upper trough will slowly cross MN and WI tonight through
Sunday. This trough has slowed down, weakened, and trended
southward compared to previous forecasts. This trough will help
enhance northeast flow off Lake Michigan and keep southeast WI
cooler (high of mid-upper 70s, cooler along the immediate
lakeshore). Our forecast highs may be a little too warm. Expect
isolated to scattered showers to develop during the daytime
hours, with a westward progression of them as the day goes on.
Forecast soundings show very shallow moisture and instability
due to steeper low level lapse rates, so I opted to remove
thunder chances and kept pops in the 15-23 percent range.

Cronce

&&

.LONG TERM...
Issued 220 PM CDT Sat Jul 4 2026

Sunday night through Saturday:

Shortwave upper riding is expected to extend from the central Great
Plains into the Great Lakes for Mon-Tue. A sfc ridge will also
reside over the region during this time. Typical warm summer days
in the 80s is forecast.

As the shortwave upper ridge flattens, the upper level flow will
become wnwly for the remainder of the week. There will be
an organized shortwave trough and cold front in the flow either
arriving late Wed or Thu. Warm and humid conditions will be in
place ahead of this feature with potential MCS development. Rain
chances of 60-70 percent are forecast. Sfc ridging and high temps
in the lower 80s will return for Fri- Sat.


Gehring

&&

.AVIATION...
Issued 650 PM CDT Sat Jul 4 2026

Most of the scattered shower and thunderstorm activity has
pushed away from area TAF aerodromes. The only exception is a
rogue storm over southeastern Columbia county which, if it holds
together, would potentially affect the MSN aerodrome around
0030z (730pm). A widely scattered showers are possible through
the overnight hours but this will be the exception rather than
the rule.

Next concern is light winds, a moist airmass, and increased
moisture for areas that received rain today resulting in patchy
fog. Not to mention perhaps a little smoke during the mid
evening from area fireworks. Guidance is not bullish on the
patchy fog potential, so confidence is shaky. Have introduced
6SM at all sites from 03z onward. A signal that is increasing is
the potential for stratus moving in from the east toward
daybreak Sunday. MVFR ceilings, with a period of IFR possible
during the mid/late morning hours. Have included with this
forecast and will refine with updates. Ceilings should rise to
VFR later Sunday afternoon. Winds will be out of the east
northeast.

Gagan

&&

.MARINE...
Issued 220 PM CDT Sat Jul 4 2026

High pressure around 30.1 inches over the Upper Great Lakes
will remain in place through Monday. Weak low pressure around
29.9 inches will slowly move east across northern Illinois into
Indiana during this time. Scattered showers and some
thunderstorms are expected over mainly the south half of Lake
Michigan through this evening. Additional showers are possible
Sunday. Areas of dense fog developed over Lake Michigan, mainly
in central portions, and is expected to expand southward
overnight. The Marine Dense Fog Advisory may need to be
expanded. There is an expectation that the fog would diminish
by mid Sunday morning with increasing northeast winds.

Cronce

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory...LMZ366-LMZ565-LMZ567-LMZ643-LMZ644-LMZ645-
     LMZ646-LMZ669-LMZ671-LMZ673-LMZ675-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876 until 10 AM Sunday.

&&

$$

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