NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 040937 AAA
AFDMKX

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

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected at times
  mainly later this morning into early this evening. The risk
  for severe storms is low, but cloud to ground lightning and
  localized gusty winds are possible with any storms.

- Patchy fog may linger into middle morning, mainly in low lying
  areas. More fog is possible later tonight into Sunday morning.

- There are mainly small chances for thunderstorms Sunday
  afternoon.

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

&&

.UPDATE...
Issued 437 AM CDT Sat Jul 4 2026

Patchy fog may occur into the middle morning hours, mainly in
low lying areas. More fog is possible later tonight into Sunday
morning, as winds remain light and moisture lingers from
possible showers and storms later today.

The main area of showers and thunderstorms over east central
Iowa continues to slowly shift eastward early this morning, in
line with Corfidi Vectors and where the low level jet nose has
its focus. The effective frontal boundary is in that area as
well. CAMs for the most part keep this activity south of the
area into the early to middle morning hours. There may still be
a few showers or storms that develop over southern portions of
the area, with some weak frontogenesis around 850 mb. This
should be few and far between.

Still anticipate scattered showers and storms to develop later
this morning into early this evening, as the main 500 mb
shortwave trough shifts by the area with peak heating. The
upward vertical motion is not robust, so would expect more of a
scattered nature to any showers and storms. As winds shift
northeast to east closer to the lake by midday and spread west
this afternoon, the mean layer CAPE may weaken and limit the
shower and storm potential.

Also, will watch to see if an MCV develops from the current
activity in Iowa, which models do not handle well and may be a
focus for shower and storm development if it can move into
southern Wisconsin.

There may be enough mean layer CAPE and shear to bring
localized gusty winds, along with the main hazard of cloud-to-
ground lightning. Those with outdoor plans today into this
evening should stay weather aware and go indoors if storms
approach.

Middle to high clouds may linger at times today, which may keep
highs in the lower 80s over most of the area. In addition, winds
should shift to the northeast and east closer to the lake by
midday and spread west this afternoon. This may bring some
cooler temperatures to these areas.

Wood

&&

.SHORT TERM...
Issued 1143 PM CDT Fri Jul 3 2026

Today and Tonight:

The weather pattern is a bit messy across the region early this
morning. Multiple rounds of convection have resulted in a good
amount of overturning, with a decent amount of CIN and around
500 J/kg of CAPE. Evening storms have shifted deeper into IL and
lingering light rain showers will gradually end over the next
couple of hours.

Convection is perking back up in Central IA in response to an
increasing low level jet, with other convective complexes
growing over NE and the Dakotas. System motion vectors are
easterly to east southeasterly overnight and with lingering
boundaries south of the region, shower/thunderstorms chances
will trend toward the slight category, with chances in our far
southwest toward daybreak pending the behavior of the convection
in IA/NE.

Saturday will once again be warm/humid with weak deep shear
(25kt) and MLCAPE around 1500 J/kg give or take. Overall there
is a lack of focusing mechanisms Saturday, which results in a
rather uncertain PoP forecast. Certainly there will be enough
heating to pop scattered showers/storms from late morning
through much of the afternoon. Given CAPE/shear profiles,
organized severe weather is not expected, though pulse-like
localized downbursts are plausible.

A potential fly in the ointment for tomorrow is whether or not
convection to our west tonight develops an MCV or lingering vort
max. While there are no model indications of this, the
potential is there given ongoing convection.

Assuming no MCV/vort activity Saturday afternoon, there should
be a gradual downward trend in shower/storm chances heading into
the evening hours. There has also been a very distinct signal
in the guidance to produce easterly flow spreading in across
Lake Michigan into southern Wisconsin during the late afternoon
and evening hours. This may induce a lake breeze and further
shunt rain chances to the west with time.

Gagan

&&

.LONG TERM...
Issued 1143 PM CDT Fri Jul 3 2026

Sunday through Thursday:

Scattered shower/storm chances will linger into at least the
first half of Sunday and an upper trough shifts to the
southeast. From a large scale perspective, this trough passage
will result in a pattern change, with the eastern CONUS ridge
breaking down and a ridge building over the Rockies.

Northwest flow aloft will send a few waves our way from time to
time next week with some signal for a decent upper wave passing
through in the Wed/Thu timeframe. Otherwise expect seasonable
temperatures with lows in the 60s and highs in the low/mid 80s.
Dewpoints will be less oppressive for the first half of the
week, dropping back in the low/mid 60s.

Gagan

&&

.AVIATION...
Issued 437 AM CDT Sat Jul 4 2026

Patchy fog may occur into the middle morning hours, mainly in
low lying areas. More fog and low ceilings below 1000 feet AGL
is possible later tonight into Sunday morning, as winds remain
light and moisture lingers from possible showers and storms
later today.

A few showers or storms may develop over southern portions of
the area this morning. Still anticipate scattered showers and
storms to develop later this morning into early this evening.
Expect more of a scattered nature to any showers and storms. As
winds shift northeast to east closer to the lake by midday and
spread west this afternoon, cooler and more stable air off the
lake may limit the shower and storm potential for terminals
closer to the lake. Localized gusty winds may occur with any
storm.

Middle to high clouds may linger at times today. Light winds
should shift to the northeast and east closer to the lake by
midday and spread west this afternoon. Light north to northeast
winds are expected tonight.

Wood

&&

.MARINE...
Issued 437 AM CDT Sat Jul 4 2026

High pressure around 30.4 inches will remain well north of the
region today and tonight, shifting east to over James Bay on
Sunday. Weak low pressure around 29.9 inches will develop and
slowly move east across northern Illinois into Indiana during
this time. Scattered showers and some thunderstorms are expected
at times through the weekend.

Fog, possibly dense at times, will be possible mainly over the
northern portions of the lake, as warm and humid air flows over
the relatively cooler lake waters. Shower and thunderstorm
chances will end Sunday night, with quieter weather for the
start of next week.

Wood

&&

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

$$

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