503
FXUS63 KMKX 022010
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
310 PM CDT Wed Jul 2 2025

.KEY MESSAGES...

- There are small chances for thunderstorms this afternoon and
  evening.

- There are chances for thunderstorms Thursday afternoon and
  night. Gusty winds may occur with any stronger storms.

- Very warm and humid conditions for Independence Day and
  Saturday, with heat index values in the middle to upper 90s.

- Better chances for thunderstorms late Saturday into Saturday
  night, perhaps lingering into Sunday. Locally heavy rainfall
  is possible.

&&

.SHORT TERM...
Issued 310 PM CDT Wed Jul 2 2025

Tonight through Thursday night:

Observing some scattered development of thunderstorms over
northeastern WI at the moment, most likely associated with a
weak zone of confluent surface flow and attendant 500mb thermal
ridge. These features (as well as the thunderstorms themselves)
are expected to track southeastward with the steering-level flow
over the next few hours. For the few weak towers of cumulus
trying to initiate convection overhead, I can only afford 10 to
15% precipitation chances at the moment (it would be isolated at
best later this afternoon and evening). I have slightly higher
(25%) chances for precipitation in east-central wisconsin
(towards Sheboygan) later this afternoon / early this evening to
account for the convection to our north grazing by.

Both the diurnal cumulus clouds and the thunderstorm chances
will decline as the sun sets this evening, with dry weather
expected late tonight into Thursday morning (only 5-10% chances
for a stray weak storm).

For Thursday, a warm front progressing northward through the
region will lead to slightly higher (15-30%) chances for
thunderstorms, mainly from 1 PM CDT and onwards into Thursday
night. Storms would be relatively brief and isolated (scattered
at best), and if one or two of them were to phase perfectly with
daytime heating (and fire in the mid afternoon through early
evening), some gusty winds would be possible. Considering that,
just a level 1 out of 5 severe threat. A lake breeze is not
guaranteed on Thursday, but most models do allow one to form and
push it at least 1 county inland (with easterly winds behind
it). Light southwesterly surface winds (behind the warm front,
further inland) will attempt to counteract this lake breeze.

Sheppard

&&

.LONG TERM...
Issued 310 PM CDT Wed Jul 2 2025

Friday through Wednesday:

Main story for Independence day and Saturday is the heat, with
daytime high temps around 90 / low 90s and heat indices in the
upper 90s expected. A modest south-southwesterly breeze is
expected Friday, and is expected to mostly counteract the lake
breeze (though the immediate vicinity of the Lake MI shoreline
could see some ventilation from due south winds over the lake).
Otherwise, it should be hot region-wide. Not expecting any
thunderstorms / precipitation on Independence day (15% chance or
less). The instability to fuel a storm will be present, but we
lack any meaningful perturbation to initiate convection.

Saturday`s southwest wind field should become strong enough to
prevent the lake breeze, and may become gusty (currently
forecasting 25 MPH gusts). Better chances for showers and
thunderstorms arrive late Saturday into Saturday night as the
low pressure system and cold front approach from the west
(30-60% chances). Front-parallel wind shear and PWAT values
approaching 2 inches would suggest a threat for training
convection and localized heavy rainfall.

40-50% shower and thunderstorm chances linger into Sunday on
account of the continuation of the cold front passage (ECMWF
solution) or wrap-around showers on the back side of the low (other
model solutions).

Sheppard

&&

.AVIATION...
Issued 310 PM CDT Wed Jul 2 2025

Rest of Today:
Diurnal cumulus clouds at scattered to broken coverage have
risen to roughly 6,000 ft AGL. Isolated to widely scattered
thunderstorm development remains possible later this afternoon
into this evening (15-25% chance) but the odds remain low enough
to avoid PROB30 groups in the majority of TAFs for now. If they
were to develop, initial cumulonimbus cloud bases would be
around the same altitude (6,000 ft). With some widely scattered
storms evident on radar to our north (northeastern WI as of 2:30
PM, tracking southeastward on the mean wind), a PROB30 group may
become necessary at KSBM on a later amendment.

Tonight and Thursday:
For tonight, cumulus clouds dissipate as the sun falls, leaving
mostly clear skies and continued VFR overnight. Cumulus
redevelop at a similar altitude for Thursday, with 15-30%
chances for thunderstorms Thursday afternoon through Thursday
night (due to a passing warm front). Light southwesterly surface
winds expected inland, with a chance for a lake breeze (due east
winds) pushing 1 or 2 counties inland by the late afternoon.

Sheppard

&&

.MARINE...
Issued 310 PM CDT Wed Jul 2 2025

High pressure around 30.0 inches will linger across the Middle
Mississippi River Valley today into Thursday, before moving to
the east by Friday. Light southwest to west winds will continue
today into tonight. Light north to northeast winds Thursday into
Thursday night will shift south to southwest on Friday, as a warm
front moves north through the region.

South to southwest winds will then increase Friday night into
Saturday night, as low pressure around 29.6 inches moves across
Lake Superior and Ontario and pulls a cold front through the
region. Expecting west winds behind this front on Sunday, veering
north into Sunday night.

There will be small chances for showers and thunderstorms at
times this afternoon and evening, mainly over the northern half of
the lake. Additional small chances Thursday afternoon through
Thursday night, focused on the southern half of the lake. More
widespread chances for showers and thunderstorms expected later
Saturday into Sunday as the cold front crosses the lake.

Sheppard

&&

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

$$

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