NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 300030 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
730 PM CDT Wed Jul 29 2026

.KEY MESSAGES...

- Warm and humid conditions return Thursday.

- Chances for showers and weak thunderstorms at times from
  Friday morning through Friday night (65-85% chances). Chances
  gradually taper down through Saturday.

&&

.UPDATE...
Issued 730 PM CDT Wed Jul 29 2026

Patchy fog is possible tonight in the Wisconsin River Valley and
other low lying areas west of Madison and Janesville. This is where
dewpoints are a little higher (around 60) due to return flow
around the high. Low temperatures tonight will be around 60,
with upper 50s possible in low spots and areas just west of the
Kettle Moraine.

While there is some smoke in the upper levels (enough for an
orange sunset), it is not expected to reduce visibility at the
surface.

Cronce

&&

.SHORT TERM...
Issued 130 PM CDT Wed Jul 29 2026

Tonight through Thursday night:

Dry and quiet weather continues through the period, with high
pressure established across the Great Lakes region. HRRR model
output and GOES Geocolor images do hint that some wildfire smoke
is present aloft, leading to a thin haze in the clear skies,
particularly for areas west of Madison / Janesville. The
synoptic subsidence associated with the high pressure could
(potentially) cause some of this smoke to reach the boundary
layer and mix down to the surface later today into tonight,
though it would likely be quite sparse / dilute by the time that
occurs. Our best guess is that surface visibility will remain 6
SM or greater, with only trace amounts of it. A similar story
for Thursday, with area-wide potential for trace amounts of
smoke.

The centroid of the high pressure shifts southeast of the region
Thursday, with light southwest surface winds allowing for a
brief return of heat and humidity. Forecast high temps in the
mid to upper 80s, with dewpoints in the mid 60s.

Sheppard

&&

.LONG TERM...
Issued 120 PM CDT Wed Jul 29 2026

Friday through Wednesday:

A positively-tilted 500mb trough tracks southeastward across the
midwest late this week, with a corresponding surface low developing
near Nebraska / the Dakotas late Thursday and crossing Illinois
Friday night into Saturday morning. The track of this system (south
of our region) should strongly limit the buildup of instability,
with most guidance suggesting ~500 joules or less MUCAPE. As such,
we're expecting showers and weak thunderstorms to gradually
overspread southern WI from west to east on Friday (65-85%
chances). Shower and weak storm chances continue into Friday
night and taper down into Saturday. Though overall precip
chances are relatively high with this event, a known bias in
long-range model guidance is to over emphasize the synoptic
features (ex. the precip shield on the north edge of the low)
with the forecast QPF then shifting south towards the
instability axis / deep convection when high-res model guidance
enters the picture. As such, it's too early to "guarantee"
rainfall across all of southern WI at this time, but the odds
are high for at least some of the region to receive some much-
needed rainfall. Our highest confidence in precip is over far
southwestern WI.

Predominantly dry weather expected Sunday into Monday as high
pressure settles into the region. A slow warming trend unfolds early
next week as the high continues southeastward. The upper ridge axis
passes overhead Tuesday, suggesting that the warmth (perhaps mid to
upper 80s high temps) may peak then. Predominantly zonal flow
looking likely in the jet through next week, though a few ripples
merit some slight chances for showers and thunderstorms in the
extended forecast.

Sheppard

&&

.AVIATION...
Issued 730 PM CDT Wed Jul 29 2026

Clear skies tonight will give way to scattered diurnal cumulus
clouds with bases around 5000 ft by mid morning. Winds will
become southerly but remain light. Patchy fog is possible west
of Madison, especially in the Wisconsin River Valley tonight.
While there is some light smoke in the upper levels (enough for
an orange sunset), it is not expected to reduce visibility at
the surface. In the upper levels, we will see an improvement
overnight and then a return later Thursday afternoon.

Cronce

&&

.MARINE...
Issued 120 PM CDT Wed Jul 29 2026

The ongoing light northerly winds will transition to light and
variable in a north to south manner as high pressure around 30.0
inches builds into the Great Lakes region today. The centroid
of this high should slowly shift southeast of Lake Michigan on
Thursday, allowing for light southerly winds Thursday and
Thursday night.

Low pressure develops near Nebraska / the Dakotas late Thursday,
deepening to around 29.6 inches before crossing Illinois Saturday
morning. Light south winds turn southeast and accelerate over the
southern half of the lake Friday, backing northeast with 15-20
KT gusts Saturday morning, then north-northeast with gusts up to
25 KT Saturday afternoon and evening. An additional period of
breezy north winds may unfold Sunday afternoon and evening as
high pressure builds over Lake Superior (20-30 KT possible).
Slower winds and gusts expected over the north half of Lake
Michigan through the aforementioned timeframes.

Sheppard

&&

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

$$

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