NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 121959
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
259 PM CDT Wed Aug 12 2026

.KEY MESSAGES...

- An isolated storm is possible in central Wisconsin this
  evening, but no severe weather is expected.

- Widespread fog is expected again tonight into early Thursday
  morning, with patchy dense fog possible, especially along Lake
  Michigan and in low-lying areas.

- Unsettled weather continues through the weekend, with on and
  off showers and thunderstorms expected. Chances for severe
  storms increase into the weekend, but timing and intensity
  remain uncertain at this time.

- Near normal to below normal temps are expected through the
  weekend and into next week.

&&

.SHORT TERM...
Issued 259 PM CDT Wed Aug 12 2026

Tonight through Thursday night:

A weak warm front at 850 mb currently draped across central
Wisconsin will be the focal point for isolated showers and
storms (15% chances) this evening into tonight. No severe
weather is expected, but lightning may develop. Storms will end
into the early overnight hours. Patchy smoke may build down
across southwestern Wisconsin this evening into tonight, but is
not expected to be widespread.

Overnight tonight, winds calm and temperatures fall to the
dewpoint. Widespread fog is expected once again. Patchy dense
fog is possible, especially near Lake Michigan where the cooler
lake waters allow for fog development earlier, and in low-lying
areas where the cooler air is able to pool.

A shortwave propagates southeastward through the northern High
Plains and Great Plains tonight to phase with the stationary
front still draped across central Iowa to central Illinois,
bringing the next chances for widespread storms by Thursday
morning. Currently, with the front staying so far south,
expecting any severe weather to stay south of Wisconsin.
However, a MCS looks to be a viable solution on most CAMs going
into Thursday morning. The northern portion of this MCS with
weaker winds and primarily rain and lightning threat will impact
southern Wisconsin from I-94 southward. Lack of instability is
the main inhibiting factor for severe, as MUCAPE over southern
Wisconsin into Thursday morning remains below 1000 J/kg. Bulk
shear values in the 50-60 kt range and PWATs of 1.5-1.75 inches
lends credence to fast-moving storms with locally heavy
rainfall.

A boundary from this complex/the quasi-stationary front looks
to linger across southern Wisconsin into Thursday as low
pressure lifts from the central Plains into the Middle
Missouri Valley. Instability (MUCAPE) builds back into the
750-1000 J/kg range during the afternoon hours, allowing for
additional isolated to scattered shower and thunderstorm
development. These storms are not expected to be severe. If the
morning storms are strong enough, they may prevent additional
instability and keep southern Wisconsin out of the thunderstorm
threat entirely.

Thursday night, low pressure continues to slowly lift northward,
bringing continued chances for showers and storms to southern
Wisconsin as the associated warm front and upper level WAA
lifts back into southern Wisconsin. Currently not anticipating
severe activity with these storms as CAPE remains minimal and no
firm focal point for MCS development exists.

MH

&&

.LONG TERM...
Issued 259 PM CDT Wed Aug 12 2026

Friday through Wednesday:

Rain and storms continue to lift northward through Friday
morning. As the warm front over the region begins to move away
Friday afternoon and a surface high pressure system with upper-
level ridging settling in, there is a potential for a break in
PoPs. However, lingering high humidity Friday night could
sustain the precipitation chances overnight (30-40%).

Following this shift, a surface low from the Plains into the Great
Lakes region brings the chance of precipitation back Saturday
(40-60%). The presence of a warm front and WAA favor these odds,
but there is uncertainty in severe potential. Instability behind
the warm front could create thunderstorm development, but low bulk
shear and the jet stream remaining to the north does not favor a
severe pattern. Despite this chance at this point remaining
unlikely, the location of the low and CAPE could cause severity.

The cold front following the warm late Saturday into Sunday could
keep the PoPs chances in the CWA, but upper-level zonal flow and a
high pressure system moving in from the Plains will push a drier
airmass into the region early next week.

Zawlocki

&&

.AVIATION...
Issued 259 PM CDT Wed Aug 12 2026

Ceilings will continue to gradually lift through the evening,
with MVFR to VFR ceilings expected before sunset. Between 03Z
and 06Z, expecting a return to 1-3 SM visibilites as widespread
fog develops. Patchy dense fog (1/4 to 1/2 SM) may develop
along Lake Michigan terminals and in low-lying areas. Fog will
gradually lift into Thursday morning. A complex of rain and
storms is expected to progress west to east Thursday morning
into Thursday afternoon, keeping lower ceilings and visibilities
across the region, especially from the I-94 corridor southward.
Primary hazard with this system is expected to be lightning.
Isolated to scattered thunderstorms then possible during the
afternoon hours Thursday across the same area. Light and
variable winds are expected throughout the TAF period.

MH

&&

.MARINE...
Issued 259 PM CDT Wed Aug 12 2026

A stalled frontal boundary just to the south of Lake Michigan will
remain into mid day Thursday before retreating south toward the Ohio
River Valley. Periodic rain, storms and patchy fog will be
possible across the southern half of the lake until this front
moves south. Light and variable winds are expected across the
Lake into Thursday night.

High pressure around 30.3 inches is expected to build down from
Ontario into the eastern Great Lakes Thursday night into Friday.
Northeast to east winds will increase across the lake becoming
breezy as the high pressure builds in and a low pressure system
develops across the Central Plains. As the low pressure around 29.9
inches moves northeast toward the Great Lakes Region, the high
pressure will be slowly moving northeast toward the New England
States. Winds will turn to southeasterly and remain breezy Saturday
ahead of the approaching low. With onshore breezy winds, conditions
may approach small craft conditions for nearshore zones. This low is
expected to track across the Lake late Saturday into Sunday. Rain
and thunderstorms will be possible across the Lake Saturday into
Saturday night. As the low exits to the northeast Sunday, high
pressure around 30.2 inches is expected to move in from the northern
plains for early next week.

Patterson

&&

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

$$

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