NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 311044 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
544 AM CDT Mon Aug 31 2026

.KEY MESSAGES...

- Heat & humidity continues through at least mid-week. Afternoon
  heat indices in the low-mid 90s expected each day, with upper
  90s to near triple digits possible in areas experiencing more
  sunshine.

- Slight chances (~15-30%) for afternoon/evening storms today and
  Tuesday. An isolated severe storm with hail or gusty winds
  can't be ruled out if development occurs.

- Periods of off/on showers and storms linger through the second
  half of the week.

&&

.UPDATE...
Issued 544 AM CDT Mon Aug 31 2026

Widespread showers and storms have developed across the eastern
forecast area early this morning under a low level jet. Plenty
of forcing with warm air advection aloft and moderate
instability to maintain these storms until they exit to the east
over the next 1 to 2 hours. Mainly dry weather and partly cloudy
skies are expected through the remainder of the morning behind
these storms. Will be watching the next area of lift currently
near the Nebraska/Kansas border as it heads toward southern
Wisconsin later today. Will maintain some precip chances
mid/late afternoon into the evening, as this feature may kick
off another round of showers and storms across the forecast
area. Otherwise, warm and humid conditions are still expected
today with the decent break in precip allowing for plenty of
time to warm up.

DDV

&&

.SHORT TERM...
Issued 1210 AM CDT Mon Aug 31 2026

Current Overnight through Tuesday night:

Synopsis/Mesoanalysis: A broken band of showers continues to march
east across the area late this evening. Initially triggered by low
level warm advection over Iowa, activity has steadily waned with
eastward extent as it moves off the core of the low level jet. Could
still nevertheless see some scattered showers continue east all the
way to the Lake Michigan shoreline through 1 AM, with hazards not
anticipated. Currently moving through the Dakotas, a cold front will
very slowly approach from the northwest through Monday night, likely
stalling near or just north of the area by Tuesday. The boundary's
slow progression will keep southern Wisconsin entrenched within a
warm and humid warm sector through the duration of the period, with
afternoon heat indices in at least the low-mid 90s anticipated.
Upper 90s heat indices are possible in locations experiencing breaks
in cloud cover. Off & on thunderstorm chances will remain a
consistent part of the forecast picture, particularly in the
vicinity of the low level jet during overnight periods. Capping &
nebulous synoptic forcing away from the front leaves the coverage &
location of any daytime storm development uncertain, with trends
needing to be monitored. In the event any daytime development
occurs, an isolated stronger storm with hail or gusty winds would be
possible.

Rest of Overnight: Will be watching for areas fog development,
particularly across the west where precip has ended and breaks in
the clouds have materialized. Not currently expecting a dense fog
threat given variability to winds and sky cover, but will keeping
tabs on vis trends. Anticipating another scattering of LLJ-
affiliated storm development during the predawn hours, with greatest
potential across the east where 850-700 mb layer temperatures will
remain a touch cooler. Not expecting any severe hazards in this
activity.

Monday afternoon & Tuesday afternoon: With prolonged periods of dry
conditions forecast, will be watching heat index trends closely, as
a warm and very humid air mass will be supportive for 90+ degree
readings. Current forecast shows readings in at least the low-mid
90s, with upper 90s readings occurring in areas experiencing greater
sunshine. Should any upward trends occur, may need to consider
possible Heat Advisories across parts of the area each day. Will
continue to provide updates. The warm/humid air mass will also be
ripe for storm development, though an absence of larger-scale
triggers makes daytime storm development uncertain. Smaller scale
features such as MCV's and outflow boundaries will thus play a large
part in each day's storm potential. Have kept precip probabilities
on the low (~30% or less) end during each afternoon period given the
uncertainty. Will be monitoring the evolution of ongoing convection
in the Central Plains, as any resultant MCV's would be poised to
track favorably across southern Wisconsin ~2-8 PM Monday
afternoon/evening (& act to enhance precip potential). Later
forecasts will evaluate these trends & update precip probs if
necessary.

Quigley

&&

.LONG TERM...
Issued 1210 AM CDT Mon Aug 31 2026

Tuesday night through Sunday:

Synopsis: The slow-moving cold front approaching during the short
term period will continue into the area on Wednesday, with global
forecast guidance beginning to hint at its northward return as a
warm front through the second half of the work week. Above normal
temperatures and muggy conditions are thus becoming favored into
next weekend, though it remains uncertain if the combined heat and
humidity will reach the very uncomfortable levels anticipated during
the short term period. This will be a trend to monitor over coming
forecasts. Given the lingering surface front & still warm/muggy
conditions, additional periods of showers and storms are anticipated
through at least the beginning of next weekend. Whether or not any
storms could be strong/severe remains uncertain, with trends being
monitored through the first half of this week. While not yet
conclusive across all global guidance, some solutions hint that
building high pressure over the Quebec-Ontario vicinity could begin
ushering in drier air by the second half of next weekend. If these
signals were to verify, a more seasonable pattern change would be in
store for Sunday & just beyond the current long term period.

Quigley

&&

.AVIATION...
Issued 544 AM CDT Mon Aug 31 2026

Widespread showers and storms in the eastern forecast area will
continue over the next 1 to 2 hours. Mainly dry weather and
partly cloudy skies are expected through the remainder of the
morning behind these storms. Could see another round of
showers/storms later afternoon into the evening. VFR conditions
are likely to continue today and tonight, outside of briefly
lower ceilings and visibilities within thunderstorms.

Low level wind shear will continue through the early morning
hours, with breezy southwest surface winds then expected mid-
morning through the afternoon. Winds will likely become light
and variable tonight.

DDV

&&

.MARINE...
Issued 1210 AM CDT Mon Aug 31 2026

A warm front is draped over central Lake Michigan this evening,
resulting in generally southerly winds across the southern half of
the waters with northeasterly breezes further north. The boundary
will attempt to work northward from the remainder of the overnight
through Monday, bringing a breezy south-southwest wind shift in its
wake. Areas remaining north of the front will continue to see east-
northeast winds. Similar to today, south-southwest winds will become
breezy once again on Monday afternoon, when 25-30 knot gusts are
anticipated over at least the southern two-thirds of the waters.
Gales are not anticipated. Periods of showers and storms continue
through the overnight hours tonight, with severe weather not
anticipated.

998 mb low pressure will shift from the Canadian Great Plains into
Ontario Monday night through Tuesday, ultimately reaching the
southern shores of the Hudson Bay by daybreak Wednesday. The
advancing low will pull a slow-moving cold front over Lake Michigan
in the process, with north-northeast winds establishing in the wake
of the boundary. Whether the front clears entirely south of the
waters or stalls out somewhere over the lake remains uncertain. With
the front in the vicinity, shower and storm chances thus continue
Monday night through at least mid-week. A few stronger storms with
gusty winds and hail are possible during this time frame. If the
front remains close to stationary through the first half of the
week, it will ultimately clear south of Lake Michigan by Thursday,
bringing northeast winds for the end of the week.

Small Craft Advisory conditions have tapered this evening in
nearshore zones. Breezy south-southwest winds are expected once
again on Monday, when gusts to or slightly above 20 knots are
forecast. A few gusts could briefly approach 25 knots, but aren't
expected to be widespread enough to warrant Small Craft Advisories
at this time. Will nevertheless be monitoring trends. Shower and
storm chances continue from the remainder of the overnight through
at least mid-week. A few stronger storms with gusty winds and hail
are possible during the afternoon/evening hours on Monday and
Tuesday.

Quigley

&&

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

$$

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