NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 271857
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
157 PM CDT Thu Aug 27 2026

.KEY MESSAGES...

- Areas of fog in the WI River Valley and other low lying areas
  of south central WI late tonight into early Fri AM.

- Multiple periods of showers and storms forecast from this
  weekend into early next week, with a sharp transition to
  warmer and more humid conditions.

- Small Craft Advisory-criteria conditions return to the
  nearshore waters Saturday afternoon through Sunday,
  particularly for zones north of Milwaukee. A Beach Hazard
  Statement may also be needed this weekend.

&&

.SHORT TERM...
Issued 145 PM CDT Thu Aug 27 2026

Tonight through Friday night:

High pressure builds into the region from the north, leading to
dry and quiet weather through the period.

As seen on current regional satellite views, an easterly lake
breeze has pushed roughly 10 miles inland from Lake Michigan
(against the synoptic northwest flow), reducing the diurnal
cumulus cloud cover and holding temperatures several degrees
cooler than inland. It should push at least an additional 10
miles or so inland before both wind-fields weaken and skies
clear this evening.

Calm winds expected tonight, with mostly clear skies allowing
for good radiational cooling. Similar to what we observed this
past morning, we could see areas of fog develop in inland areas,
particularly low-lying marshy areas and river valleys. Pockets
of this fog could become dense, particularly the WI River
Valley.

A light due-west breeze develops into Friday, with a southeast
lake breeze along the shoreline. Some 5-10% precip chances are
included along the lake breeze Friday afternoon in the off
chance that it can produce an isolated shower.

Sheppard

&&

.LONG TERM...
Issued 145 PM CDT Thu Aug 27 2026

Saturday through Thursday:

Synopsis:
The longwave upper ridge axis currently over the Rocky
Mountains will build eastward into the midwest this weekend into
early next week, yielding return flow (warm and humid air) and
active weather.

Discussion:
Broad low pressure over the Great Plains on Saturday will induce
a south breeze across the CWA. The nose of the 850mb LLJ builds
into western WI Saturday morning, yielding chances for showers
underneath it. Our CWA should remain predominantly dry through
the Saturday AM hours, with just a few shower chances near and
north/west of the Dells). The LLJ and associated WAA gradually
drift east into the region later Saturday through early Sunday
morning, with showers likely to move in with it (50-65% rain
chances, mainly overnight). The LLJ undergoes it's typical
nocturnal intensification Saturday night, delivering very strong
850-700mb WAA, but also leaving the mid level lapse rates and
instability fairly limited. Rumbles of thunder are certainly
possible with this activity, but we have no concern for severe
wx at this time.

The surface warmth and humidity (highs in the mid 80s and dewpoints
around 70) arrive Sunday, with a continued southerly breeze. The
nose of the LLJ (and the strongest WAA and highest precip chances)
track northeastward out of our region, but the LLJ does remain
overhead, with continued precip chances and sharpening mid level
lapse rates / instability. From Sunday through midweek next week,
ECMWF and GEFS ensembles continue to resolve an active weather
pattern, with a combination of similar LLJ / WAA driven precip,
as well as surface-850mb baroclinic zone driven precip,
yielding occasional chances for showers and thunderstorms. PWAT
around 1.75" (briefly higher to 2") and modest instability are
resolved on some ensemble members. Locally heavy rainfall and
strong thunderstorms will be possible somewhere in the midwest
region, no clarity on exactly where or when just yet. The heat
and humidity (highs in the mid to upper 80s, dewpoints around
70) linger early next week, likely remaining above seasonal
norms through midweek.

Sheppard

&&

.AVIATION...
Issued 145 PM CDT Thu Aug 27 2026

Scattered to broken diurnal cumulus around 5,000 ft linger
through the afternoon, eroding into the evening. Light northwest
winds for most areas, a weak easterly lake breeze and clearer
skies for the Lake MI shoreline. Continued dry weather and VFR
today into tonight.

For late tonight into early Friday morning, some potential for
fog to develop in low-lying marshy areas inland (added to the
KMSN and KJVL TAF for now). This will erode quickly after
sunrise, leaving continued dry weather and VFR for Friday.

Sheppard

&&

.MARINE...
Issued 145 PM CDT Thu Aug 27 2026

Modest northerly winds continue this afternoon as a low
pressure trough of 29.9 inches exits eastward from lower
Michigan. Winds then become light and variable tonight and
Friday as high pressure of 30.2 inches moves from the northern
Great Lakes to the lower Great Lakes.

High pressure then pulls east Saturday and low pressure of 29.7
inches will slowly approach from the Great Plains. Breezy
southerly winds are expected this weekend into early next week,
but gusts are expected to remain below gale force.

Sheppard

&&

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

$$

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