NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 010646
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
146 AM CDT Wed Jul 1 2026

.KEY MESSAGES...

- An Extreme Heat Warning remains in effect for all of southern
  Wisconsin through early this evening. Additional heat
  headlines may be needed into the rest of the week, but some
  uncertainty remains due to clouds and rain chances.

- There are chances (20 to 40 percent) for thunderstorms into
  this morning, mainly north of a Lone Rock to Sheboygan line. A
  stronger storm may produce hail, gusty winds and locally
  heavy rainfall.

- There is a small chance (20 percent) of a thunderstorm this
  afternoon northwest of Madison. A strong to severe storm with
  strong winds and hail would be possible, if it develops.

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

- 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 146 AM CDT Wed Jul 1 2026

Today through Friday night:

The Extreme Heat Warning will remain in effect until early this
evening. An extension or a Heat Advisory issuance into later in
the week may eventually be needed, depending on how many clouds
and showers/storms occur. Will likely wait on how clouds and
possible shower/storm trends play out overnight into later today
before making further decisions on the heat headlines for the
rest of the week. Heat index values in the 90s to low 100s are
forecast for Thursday and Friday.

There is a chance (20 to 40 percent) for showers and storms
developing into this morning, before pushing northeastward by
midday. The southwesterly low level jet will be the key feature
to watch, as it develops more of a nose and shifts northeastward
toward the area.

CAMs seem to be favoring scattered showers and storms developing
in southeast Minnesota into southwest Wisconsin by 09Z or so,
shifting northeast into the morning hours. Given the setup with
the southwesterly flow through a deep layer focused from Iowa
into southwest and central Wisconsin, would expect any showers
and storms that develop with the low level jet nose to push
northeast and ride the ridge through these areas.

There is a decent amount of elevated CAPE (1500 to 2500 J/kg),
with weaker deep layer bulk shear around 20 knots increasing to
30 to 35 knots in the morning. Thus, any stronger storm could
produce hail, gusty winds and locally heavy rainfall, given the
very moist airmass in place and storms possibly moving over the
same areas.

There could be an isolated storm that develops this afternoon
northwest of Madison, closer to the low level jet axis. It would
be elevated in nature, but given the high CAPE over 3000 J/kg and
30 to 35 knots of deep layer bulk shear, could see a strong to
severe storm occur.

CAMs suggest clusters of thunderstorms may develop along a
surface boundary in north central Iowa to north central and
northwest Wisconsin by early evening, then shifts east
northeast with the aid of the low level jet toward and into the
northern portions of the area during the evening and overnight.
There is enough mean layer CAPE and deep layer bulk shear for
more strong to severe storm potential, with damaging winds and
hail the main hazards. Heavy rainfall may occur as well.

The low level jet should focus more into southern Wisconsin
Thursday, with a surface boundary in the form of a stationary
front developing as well. These features may help to focus more
showers and thunderstorms at times Thursday into Thursday night,
as well as into Friday. There remains a strong to severe storm
risk with heavy rainfall as well for this period, as high CAPE
and moderate deep layer bulk shear values persist. Details on
this potential will be more clear once the convection into
tonight shows its hand.

Wood

&&

.LONG TERM...
Issued 146 AM CDT Wed Jul 1 2026

Saturday through Tuesday:

Active conditions continue into the holiday weekend, with
multiple batches of thunderstorms expected Saturday through
Sunday.

Subtropical ridging will gradually break down over the eastern
CONUS this weekend, allowing for modestly cooler temperatures
and heat indices. A slow-moving surface boundary will
concurrently slide into southern Wisconsin, supporting daily
chances for showers and thunderstorms both Saturday and Sunday.
Overall storm chances are greatest (50 to 60 percent or more)
on Saturday, when a shortwave trough is progged to move across
southern Wisconsin.

Most favored locations for storms on Sunday will depend on
where the surface boundary sets up in the wake of Saturday's
storms, with boundary location remaining a source of uncertainty
at this time. Will continue to monitor trends over coming
forecasts.

Any weekend storms will be capable of producing cloud-to-ground
lightning and heavy downpours, with a few strong to severe
storms possible. Continue to monitor the forecast is planning to
be outdoors. Widespread precipitation chances wane moving into
the beginning of next week, as broad high pressure builds over
the western Great Lakes.

Saturday/Fourth of July looks to be a potentially active
Independence Day, as an upper shortwave and surface boundary
move across the region. Aforementioned features will be
impinging upon a still unseasonably moist airmass, which will
be supportive of abundant instability. While modest, initial
forecast soundings suggest bulk shear values supportive of at
least loosely-organized convection, so will need to monitor for
some severe weather potential over coming forecasts.

Storms will also be capable of producing heavy downpours given
precipitable water values in the 1.60 to 1.80 inch or greater
range. Regardless of severity, any convection will be capable of
producing cloud-to-ground lightning, which will be hazardous to
anybody attending outdoor holiday festivities. Keep up with the
forecast if planning to be outside Saturday.

Depending on the surface boundary's location in the wake of
Saturday's storms, could see another batch of convection during
the afternoon/evening hours on Sunday. Have maintained 20 to 40
percent precip probabilities from the NBM in the evening
forecast update, given lingering uncertainties related to
surface boundary positioning.

Expect that values will continue to fluctuate with the modeled
positioning of the boundary over coming forecasts, with more
refined locations of favored storm development emerging during
the Friday to Saturday time period. Like Saturday's
thunderstorms, will need to monitor for a few severe storms with
heavy downpours, in addition to lightning potential in all
thunderstorms, in any Sunday activity.

Quigley

&&

.AVIATION...
Issued 146 AM CDT Wed Jul 1 2026

Light southwest winds are expected into this morning. Gusty
southwest winds should return by midday into the afternoon and
early evening. Removed mention of low level wind shear in TAFs
for now, as surface winds should remain high enough to limit
this potential.

There may be broken ceilings around 5000 feet AGL into this
morning for areas west and north of Madison to Sheboygan, if
some showers and storms develop. Most terminals to the southeast
of here should remain dry and may not see much in the way of
clouds during this time.

More VFR category ceilings, along with showers and storms, may
approach the Madison and Sheboygan terminals this evening and
perhaps the rest of the terminals overnight tonight. Locally
reduced ceilings and visibilities may occur in any showers and
storms. May see gusty winds and some hail with the stronger
storms during this time.

Wood

&&

.MARINE...
Issued 146 AM CDT Wed Jul 1 2026

Modest to breezy south to southwest winds will prevail into
Thursday, then lighter winds should occur into Friday, as high
pressure around 30.1 inches remains to the southeast of the
Great Lakes, while low pressure around 29.5 inches moves slowly
east across central Manitoba into James Bay.

Chances for thunderstorms are forecast across the northern half
of the lake through tonight. There are chances for
thunderstorms across the southern two thirds of the lake
Thursday into Friday evening, and across the southern half of
the lake later Friday night into Sunday. Some strong to severe
storms may occur at times, though confidence remains low with
the timing of each round of 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. There may also be some patchy dense fog along the
Lake Michigan shoreline into this morning.

Southwest winds may approach Small Craft Advisory levels today
into early this evening for the nearshore waters, mainly near
the shoreline.

Wood

&&

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

$$

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