NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 011957
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
257 PM CDT Wed Jul 1 2026

.KEY MESSAGES...

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

- Chances (40 to 70 percent) for thunderstorms later this
  afternoon into tonight. Best chances are north of a line from
  Lone Rock to Sheboygan. Some strong to severe storms with
  heavy rainfall may occur at times, mainly in the late
  afternoon and evening. Damaging winds and large hail are the
  main hazards of concern.

- There are periodic chances (40 to 60 percent) for
  thunderstorms Thursday into 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 at times,
  so keep up with the forecast.

&&

.SHORT TERM...
Issued 257 PM CDT Wed Jul 1 2026

Tonight through Thursday night:

We're in a short rain free period of the afternoon across
southern Wisconsin. Don't expect this to last long across the
area however. CAMs are really honing in on convection developing
across northern IA and southeastern MN (maybe a few cells
develop over far southwestern WI) late this evening into
tonight. On the other hand WoFS is favoring more cellular
convection developing late this afternoon and persisting into
the evening. Given the unseasonably hot and humid conditions
this is not a huge surprise to see the guidance become a bit
overzealous, but as we begin to see the whites of the storms
eyes here... its starting to look increasingly likely that there
will be another round or two of strong to severe storms. The
sfc front looks to remain to the the northwest of the MKX CWA.
There are multiple outflow boundaries scattered across the area
due to previous convection, which will provide some low level
forcing should storms develop. With all the lingering
boundaries, there is an agitated cumulus field on satellite
currently in IA/southern WI (favors some of the WoFS cellular
convection).

Now when it comes to the where of more thunderstorms, the ridge
across the eastern CONUS remains in place with far southern and
southeastern Wisconsin still under its influence. So ridge
riding storms will be the main concern. Anything that begins to
drift to the far southeast overtime should enter into a more
stable airmass and decay. This is a prime area where the CAMs
are struggling a bit as they try to make the storms go outflow
dominate (this has been the case multiple days in a row, but the
high pressure and stability are preventing anything from
blowing into southeastern WI). The best potential for strong to
severe storms overall still looks to be for areas along and
north of a line from Lone Rock to Beaver Dam to Sheboygan.
Should convection trend further south as the WoFs is suggesting
then we will see this severe potential also shift south roughly
from Platteville to Madison to West Bend.

CAPE is around 2000 J/kg (or better) for much of the area with
bulk effective shear around 30-35 kts. Mid level lapse rates are
marginal around 6 to 6.5 C/km while low level lapse rates are
much better around 7 C/km. Given all of this, our main hazards
are strong winds, hail, and heavy rain. Any storms that begin to
train will pose a flood risk.

The linchpin pin here is the timing, which boils down to.. when
does convection start to fire to our west along the sfc front.
WoFS is favoring a slightly earlier timing in the late
afternoon as it tries to get some cellular convection going,
while other short term models hold off until roughly 9 PM to 11
PM for storms to be knocking on the door in Marquette, Green
Lake, and Sauk Counties. Regardless of solutions here, storms
are expected to continue through the overnight hours and may
linger into early Thursday morning.

Additional rounds of rain and storms for Thursday through
Thursday night will be possible (chances around 20-60%). The
timing and placement of the storms will depend on how long
convection lingers early morning Thursday and how much cloud
cover remains. If skies clear quickly, then all of southern
Wisconsin could get some scattered thunderstorms (with some
stronger to severe storms possible). The exact location of the
sfc boundary will play a big roll here as well. As it stands
now, another unseasonably warm day with high CAPE and moderate
shear. Best chances for storms look to be Thursday late
afternoon into Thursday night.

The Excessive Heat Warning continues across southern Wisconsin
into Thursday night. Generally the warmest conditions are
expected across far southern and southeastern Wisconsin with
slightly cooler conditions across central Wisconsin. This will
be especially true for areas that receive rain as that will
cool conditions for a bit. Thursday will be a bit cooler
relatively speaking, but by and large high temperatures in the
90s with overnight lows in the 70s.

Patterson

&&

.LONG TERM...
Issued 257 PM CDT Wed Jul 1 2026

Saturday through Wednesday:

The active weather stretch looks to continue into the weekend.
Multiple rounds of rain and thunderstorms are expected both
Saturday and Sunday.

The ridging across the eastern CONUS will begin to slowly
breakdown Saturday, which will give the state a bit of a break
from the scorching heat. While this takes the edge of the heat,
this does open the door for active weather to persist. A slow-
moving sfc boundary will slide into southern Wisconsin as the
high pressure pulls away. As this boundary moves in there will
be rain/storms chances 30-70% through the weekend. The better
chances look to be Saturday vs Sunday. These better chances will
associated with a shortwave trough that is expected to move
across southern Wisconsin. The subsequent chances Sunday will
depend on where the sfc boundary remains.

There will be a potential for some stronger to severe storms
each day (with Sundays potential heavily depending on
the after math of Saturdays). As things stand now lightning and
heavy rain are by far the most pressing hazards. However, we
are looking at some upper level support, unseasonably moist
airmass, and forecast soundings showing some modest shear... if
things align at the right time we could see some scattered
strong wind and hail. We will be keeping a close eye on the
holiday weekend with more information on the specifics of
timing, location and severity to come. With a potentially active
Fourth of July expected, take some time to make plans for the
holiday now vs later.

Regardless of severity, heavy rain is likely with PWAT values
around 1.5 to 2 inches. Any storms that begin to train over the
same areas for multiple days could start to have flooding
concerns. Thankfully everything at this time looks to be fairly
progressive which will help limit the flooding potential.

Heading into early next week the low chances for rain look to
linger a bit, but this is by and large due to the differences
between models. Weak ridging is expected to settle in across
the central CONUS with a low pressure system aloft in the Hudson
Bay area for early next week. Each model has a difference
solution here with the exact placement and strength of the low
in Canada. The deterministic GFS even has a cut off low in the
mid Mississippi. Given the uncertainty present low POPs around
20% or less does linger at times through early next week.
Temperatures look to remain warm and more seasonable in the
lower to upper 80s for next week. Overnight lows expected to be
in the 60s.

Patterson

&&

.AVIATION...
Issued 257 PM CDT Wed Jul 1 2026

Largely VFR conditions expected for most terminals through the
period. The only instances of lower ceilings and visibilities will
be with any showers and thunderstorms that develop. With high
pressure parked over the eastern US, many of these showers and
storms are expected to ride northeast over the top of the high. This
should largely keep any storms across western and central Wisconsin.
There is a small potential (20-40%) that a decaying and broken line
of showers/storms pushes into south central Wisconsin overnight
tonight into Thursday morning, but confidence on this is low. Best
timing for this to occur would be roughly midnight to 6 AM. For
storms in central and western Wisconsin, there is currently a line
moving through this afternoon which will exit around 3 PM.
Additional storms are expected to develop in IA and MN and move
northern east into the area around 6PM to Midnight.

Within any thunderstorms ceilings are expected to be around 3 to 5
kft with visibilities around 1-3 SM under the heaviest rain. There
will be a potential for isolated strong to severe storms for
terminals along and north of a line from Lone Rock (LNR) to
Sheboygan (SBM) through tonight. Primary hazards with any stronger
storms will be 60 MPH winds, quarter size hail and heavy rain. The
threat for severe storms is expected to end around midnight. MVFR
ceilings and visibilities will remain possible through Thursday
morning for any additional rain and thunderstorms. Southwest winds
are expected through the period.

Patterson

&&

.MARINE...
Issued 257 PM CDT Wed Jul 1 2026

High pressure around 30.1 inches will remain parked over the
southern Appalachian Mountains into the weekend. Meanwhile, a low
pressure system around 29.5 inches in west central Manitoba slowly
moves east toward James Bay by Friday. Breezy south to southwest
winds will persist through Thursday. Winds will approach but
remain below Small Craft Advisory Levels through this evening in
the nearshore waters. 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 around 29.7 inches 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 will persist through Thursday afternoon
through Friday evening across the southern two thirds of the lake.
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 over
the lake.

Patterson

&&

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

$$

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