NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 040211
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
911 PM CDT Thu Jul 3 2025

.KEY MESSAGES...

- Thunderstorms will expand in coverage overnight. A few
  instances of hail and gusty winds, along with heavy rain, are
  possible.

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

- A chances for thunderstorms later Saturday into Saturday
  night, perhaps lingering into Sunday. Gusty winds and hail are
  possible late Saturday into Saturday evening, with locally
  heavy rainfall possible late Saturday into Sunday.

&&

.UPDATE...
Issued 911 AM CDT Thu Jul 3 2025

Thus far just very isolated convection has affected the region
this evening, either associated with storms moving into
southwestern Wisconsin from Iowa, or generating along the lake
breeze. Over the next few hours, convection will increase across
a theta-e axis over western and central Wisconsin, with the
highest storm coverage generally centered across the greater
I-39 and I-90 corridors. While capped for a surface-based
parcel, forecast soundings show that parcels lifted from about
850 MB (coincident with the low level jet) will have around 1500
J/KG of CAPE available. Freezing levels are fairly high, and
there is an inversion near the surface, but moderate shear may
be sufficient for a few instances of severe hail and gusty
winds. Of greater concern will be slow, back-building storm
motions and PWATs of around 2 inches, suggesting the potential
for localized areas of very heavy rain. Contemplated a small
flash flood watch for parts of the area, but given continued
uncertainties as to how widespread the very heavy rain will be,
and exactly where it will occur, will hold off for now.

Convection will reach peak coverage and intensity overnight,
likely between about 1 and 5 AM, and then gradually dissipate
between sunrise and mid morning tomorrow.

Boxell

&&

.SHORT TERM...
Issued 323 PM CDT Thu Jul 3 2025

Tonight through Friday night:

Still looks like isolated storms may develop along the lake
breeze this afternoon, or possibly towards the northwest
forecast area within the better cumulus field. Most places will
likely remain dry into early evening though given the lack of
substantial larger scale forcing.

An area of warm advection will lift into the area later this
evening into tonight and is expected to be the primary forcing
mechanism for a round of showers and storms. The persistence of
the forcing along with a lot of moisture (precipitable water
values of 1.5-1.75") may result in the thunderstorm chances
lingering from late evening into Friday morning, possibly even
impacting early morning Independence Day parades tomorrow. The
duration of the storm chances may also result in some locally
heavy rainfall tonight into Fri morning. Initial storm
development later this evening into early tonight could include
a few stronger storms with a small threat for large hail and
damaging winds. The severe threat will likely wane overnight
into Friday, with lightning and heavy rainfall the main
concerns.

Mainly dry conditions are expected Friday afternoon into Friday
night in the wake of the early Friday storms and as the better
forcing exits the area. Still expecting some clearing by the
afternoon hours to allow temperatures to warm up and approach
the 90 degree mark. Did knock the temps down a touch from the
previous forecast given the potential for clouds to hang on a
bit longer than previously expected. Even so, afternoon heat
indices may still reach the mid to upper 90s given the humid
airmass in place. Dry weather is currently expected Friday
evening into Friday night for any Independence Day festivities.

DDV

&&

.LONG TERM...
Issued 323 PM CDT Thu Jul 3 2025

Saturday through Thursday:

A shortwave and cold front will approach from the west Saturday.
Dry weather will continue through the morning and likely through
much of the afternoon, with current model timing suggesting the
better forcing and associated storms will reach the western
forecast area later afternoon into early evening. A few strong
to severe storms will be possible, especially across the
northwest half of the forecast area where instability will be
higher when the forcing arrives. Locally heavy rainfall will be
a concern again with very high precipitable water values in the
2-2.25" range. Storm chances could linger into at least Sunday,
depending on how fast the system moves through and sweeps the
deeper moisture out of here.

Hot and humid conditions are likely Saturday ahead of the
approaching cold front, with highs hitting 90 most places,
possibly pushing mid-90s in the southeast. Could see heat
indices push 100, depending on how high the dewpoints get.
A few models do show some mixing possible and "lower" dewpoints
in the 60s across at least the southeast forecast area during
the afternoon, with breezy southwest winds likely. Either way,
it will be a very warm day for any outdoor holiday activities.

Dry weather is likely Monday, with a quick return of
shower/storm chances Tue-Thu as an active shortwave pattern sets
back up across the area. Near normal temps are likely next week.

DDV

&&

.AVIATION...
Issued 911 AM CDT Thu Jul 3 2025

Thunderstorms will increase in coverage overnight across
southern Wisconsin, with Madison, Janesville, and Waukesha most
likely to see prolonged periods of storms. Gusty winds, lower
ceilings and reduced visibilities are likely with any
thunderstorms.

Thunderstorm coverage will gradually dissipate after sunrise,
likely ending by late morning. VFR conditions are expected
thereafter.

Boxell

&&

.MARINE...
Issued 323 PM CDT Thu Jul 3 2025

High pressure around 30.0 inches over the Ohio River Valley
will move to the east tonight into Friday. Light north to
northeast winds today will become east to southeast tonight.
Winds will then shift south 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 29.3 inches moves across
northern Ontario into Hudson Bay. Winds may approach Small Craft
Advisory levels over the nearshore waters on Saturday. The low
will pull a cold front through the region Saturday night into
Sunday. Northwest winds will become north behind this front
Sunday and linger Sunday night.

Mainly small chances for thunderstorms are forecast later tonight
into early Friday morning across southern portions of the lake.
More widespread chances for showers and thunderstorms are forecast
for later Saturday into Sunday, as the cold front crosses the
lake.

DDV

&&

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

$$

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