NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 021115
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
615 AM CDT Thu Jul 2 2026

.KEY MESSAGES...

- An Extreme Heat Warning remains in effect for all of southern
  Wisconsin through this evening.

- After morning showers and thunderstorms end, a brief break
  will allow for additional storms to strengthen late this
  afternoon into this evening. All hazards are possible. Storms
  will weaken overnight. Early Friday morning a decaying line of
  storms may also progress eastward through the region.

- There are periodic chances (40 to 60 percent) for
  thunderstorms throughout the holiday weekend. Some strong to
  severe storms with heavy rainfall may occur at times, though
  confidence remains low with the timing of each round of
  storms. This may impact outdoor holiday activities, so keep up
  with the forecast.

&&

.UPDATE...
Issued 615 AM CDT Thu Jul 2 2026

Showers are storms are in a weakening trend as they move
southward and the LLJ weakens into this morning. Very high PWAT
values around 2 inches will lead to the main concern this
morning being locally heavy rain and perhaps a few areas of
local flooding. However, with cells struggling to maintain
intensity not expecting this threat to be widespread. Primary
concern will be where training storms develop.

As showers and storms decay this morning, expecting the remnant
boundary to push back northward, allowing for an increase in
instability and temperatures. Areas in central Wisconsin may
struggle to see clouds dissipate, and therefore may have the
Extreme Heat Warning downgraded or canceled in that area. With a
strong EML still in place through Illinois, at this time cannot
rule out clouds dissipating all the way northward, so have kept
the Extreme Heat Warning out for all of southern Wisconsin. Keep
an eye out for updates and cancellations as the cloud cover
shows its hand this afternoon.

This evening, the remnant boundary will be the focal point of
developing additional storms. With CAPE over 2000 J/kg, shear
of 35-40 kt, and still impressive PWATs between 1.5 and 2
inches, expecting all hazards to be possible with storms that
develop.

MH

&&

.SHORT TERM...
Issued 1139 PM CDT Wed Jul 1 2026

Overnight through Friday:

Thunderstorms congealed into somewhat of a line over central and
southwest WI this evening. There are a few segments that are
tracking west to east that are organized, cold-pool-driven and
producing 40 to 60 mph winds. As these storms track into
portions of southern WI overnight, our environment support wet
microbursts with its mid level dry air, high instability, and
sufficient shear. Wind is our main concern. The northern two
tiers of counties (north of Madison and Milwaukee) are in a
Severe Thunderstorm Watch until 5 AM. The late end time on this
is to allow for storms to get across most of Lake Michigan.

As the night goes on and the cluster of storms takes on a more
east-west orientation, we are going to have an increasing
flooding risk. With PWATs pushing 2 inches, individual storms
can have 1 to 2 inch per hour rain rates, and repeated rounds
of these storms with high rainfall rates will quickly add up.

Thursday (today): A shortwave tracking through the Midwest is
expected to arrive in southern WI during the afternoon which
should trigger thunderstorms. If the overnight showers/storms
diminish in a timely manner this morning, this will give us
enough time to clear out and destabilize. The more sun, the
higher the instability for stronger storms. Overall, there will
be decent synoptic forcing to support a cluster of storms,
including the right entrance region of the upper jet, the nose
of a low level jet, and the mid level shortwave trough. With
high cape and marginal shear, wind and hail are the main
threats.

Cronce

&&

.LONG TERM...
Issued 1139 PM CDT Wed Jul 1 2026

Friday through Saturday:

The surface high that was sitting over the southern
Appalachians will gradually weaken and shift toward the Atlantic
coast Friday through the weekend. This breaking down of the
upper ridge will transition us to zonal flow across the Upper
Midwest. Weak ripples (shortwave troughs) in the mid level flow
will help to trigger rounds of thunderstorms Friday through
Saturday night. This is a weather pattern where the timing of
these ripples is uncertain. In addition, the focus of each
consecutive round of storms would likely be along an outflow
boundary from the prior round of storms, so the location is also
uncertain (could end up being in northern IL rather than
southern WI).

For Friday, another shortwave is expected to track across
central or southern WI during the day. With southern WI on the
periphery of the high heat and humidity (instability gradient),
we have a risk for severe storms. The timing and location remain
uncertain.

The heat on Friday is also uncertain, as it will depend on
where that Thursday night outflow boundary rests and ultimately
how much sun we get. It is possible that only a portion (or
none) of southern WI would need a heat advisory.

We have been watching a fairly consistent signal for a robust
shortwave trough to track across WI on Saturday. This would
likely occur during the afternoon at the time of peak daytime
heating, but that is uncertain. The GFS is showing an MCS that
could roll across southern WI Saturday morning, so that could
put a damper on the severity of any storms that develop with the
afternoon shortwave. Again, we will need to wait until the prior
day to get a better handle on timing. I realize this is a
critical time for making decisions about outdoor events and
activities during this Independence Day holiday weekend and it
is frustrating to not have all the information ahead of time.
It is important to have a plan in case of thunderstorms,
including severe.

Sunday through Wednesday:

One more shortwave trough and associated weak surface low is
expected to cross northern WI and Upper Michigan on Sunday.
Higher chances for showers and storms will be closer to this low
to our north, but steep low-mid level lapse rates in this
cyclonic flow will give us scattered shower chances all the way
down to the IL border. This low may take until Monday to clear
the Upper Great Lakes.

A welcomed return of slightly cooler and drier air is slated to
arrive by Monday. The weather should be dry Monday and Tuesday,
but another shortwave trough could bring showers and storms
again by Wednesday. We will still be warm and humid, just not
very hot like it has been.

Cronce

&&

.AVIATION...
Issued 615 AM CDT Thu Jul 2 2026

VFR to MVFR ceilings this morning, with a few heavier storms
producing visibilities below 2 SM through the morning hours.
Clouds will become VFR again and scatter out through the
afternoon before additional storms develop late this afternoon
through tonight. Generally expecting VFR ceilings, but will see
local drops to MVFR and below similar to this morning.
With the afternoon and evening storms, damaging winds, large
hail, and an isolated tornado are all possible. Storms will
become a line into the late evening hours and transition to a
wind threat, moving eastward into Lake Michigan late tonight.
Going into early Friday morning, an additional line of storms
may move eastward through the region, but confidence in impacts
is low at this time. Storms diminish into the mid-morning hours
once again.

Generally southwesterly winds through today outside of storms,
with sustained winds around 12 kt during the afternoon hours.
Winds remain southwesterly through Friday morning, but will
decrease to less than 10 kt overnight.

MH

&&

.MARINE...
Issued 1139 PM CDT Wed Jul 1 2026

High pressure will remain parked over the southern Appalachian
Mountains into the weekend. Meanwhile, a low pressure system
around 29.5 inches will track across Ontario and reach toward
James Bay by Thursday night. Breezy south to southwest winds
will persist through Thursday. Southwest winds will weaken
becoming light Thursday night through Friday. Heading into the
weekend, high pressure in the Appalachian range will gradually
shift east. As the high pressure pulls away, there is a
potential for low pressure to move into the Great Lakes Region
for the weekend.

Chances for thunderstorms (50-60%) remain across the northern half
of the Lake through tonight. Tonight into Thursday morning there is
a small chance (~20%) for rain and storms across the southern half.
The chances for storms (30-60%) will persist from Thursday
afternoon through Friday evening. Additional chances for
rain/storms remains across the entire lake Saturday and Sunday.
Strong to severe storms may occur at times, though confidence
remains low in timing of stronger storms.

Patchy marine fog will be possible at times, primarily over the
northern half of the lake as the warm and moist airmass moves
overhead.

Cronce

&&

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

$$

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