869
FXUS63 KMKX 240009
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
709 PM CDT Sun Aug 23 2026

.KEY MESSAGES...

- Crisp, fall-like conditions tonight. Some fog is possible
  after midnight.

- Comfortable & pleasant afternoon weather conditions today
  through Tuesday & Thursday-Friday.

- Windows for showers & thunderstorms Tuesday night through
  Wednesday & next weekend.

&&

.UPDATE...
Issued 709 PM CDT Sun Aug 23 2026

No major changes to the forecast this evening with high pressure
in place and the fair weather cumulus slow diminishing now that
the sun is setting. The clear skies tonight, light winds and
falling temperatures will lead to some fog development tonight.
The best potential will be in low lying areas and river valleys.
With dewpoints also expected to fall a couple degrees there is
a bit of uncertainty in how widespread fog development will be.
Otherwise with overnight lows expected to fall into the upper
40s to mid 50s (warmer near Lake Michigan), it will be a cool
and crisp night.

Patterson

&&

.SHORT TERM...
Issued 1200 PM CDT Sun Aug 23 2026

This afternoon through Monday night:

Synopsis/Mesoanalysis: Southern Wisconsin is centered between low
pressure along the Ontario-Quebec border & high pressure along the
Minnesota-Iowa border late this morning, resulting in breezy
northwest surface winds. With the center of the high & affiliated
low level subsidence well west of the area, surface heating is
allowing for fair weather cumulus development, with cumulus coverage
expected to increase further moving deeper into the afternoon.
The aforementioned surface high will nudge into southern
Wisconsin tonight, leading to clear skies and light surface
winds. The clear skies & light winds will allow for efficient
radiational cooling & fall-like low temperatures in the low 50s.
Some spots could dip into the upper 40s. Areas of fog
development are possible after midnight, particularly in low-
lying locations. Fog will quickly dissipate after sunrise
Monday, giving way to mostly sunny skies and pleasant weather
conditions Monday afternoon. High pressure will begin to shift
east of the region Monday night, allowing south-southwest winds
to re-establish across the area.

Tonight: Will be monitoring for potential fog development near/after
midnight as the boundary layer attempts to decouple in the presence
of clear skies and light surface winds. Forecast soundings show
extremely shallow near-surface moist layers susceptible to mix out
and/or dew depletion, so fog coverage remains uncertain. Suspect
that the best overall fog potential will remain confined to
river valleys & other low-lying spots, but have included broader
mentions areawide in the afternoon update. Will be monitoring
visibility trends into the overnight. Slow down, use low beam
headlights, and allow for extra following distance if
encountering areas of fog on the roads.

Quigley

&&

.LONG TERM...
Issued 1200 PM CDT Sun Aug 23 2026

Tuesday through Sunday:

Synopsis: High pressure will continue to shift east of the region on
Tuesday, with southerly return flow allowing for gradual moisture
returns and slight increases in humidity. The next upper disturbance
and surface front will drift into the western Great Lakes from the
Canadian Prairies Tuesday evening through Wednesday, bringing the
next chances for showers and thunderstorms to southern Wisconsin. A
new area of high pressure will move into the western Great Lakes
during the second half of the week, leading to pleasant and mostly
dry weather conditions Thursday into Friday. The high will shift
east by Saturday, with returning southerly flow leading to steady
increases in humidity through the remainder of next weekend.
Concurrent increases in zonal upper level flow, in addition to
embedded shortwaves, will support the next shower and storm chances
within the returning moisture. Saturday night into Sunday is the
currently favored window for storms in southern Wisconsin, with more
precise timing clarifying through this week.

Tuesday Evening through Wednesday: Still anticipating periods of
showers and storms across southern Wisconsin as an upper wave &
attendant surface cold front move through the western Great
Lakes. General idea of initial (likely elevated) storms within
an increasing warm advection regime Tuesday evening/night,
followed by a window of surface-based storm potential along the
passing cold front Wednesday afternoon, remains on track in this
forecast. Latest six hourly precip probs reflect these
expectations. Whether or not any of this activity reaches severe
levels remains less certain, however, largely due to the
currently progged timing of the best synoptic-scale ascent.
Global & longer-range mesoscale guidance is relatively insistent
on a Tuesday overnight/early day Wednesday passage of the upper
wave & surface front, which would be misaligned with peak
surface heating & the best instability. Nevertheless, prevailing
deep layer shear will be supportive of more organized storm
development through this time frame, with any combination of
factors promoting increased instability leading to higher
potential for a few severe storms with hail and gusty winds.
Will be monitoring setup and timing details closely over the
next 24-36 hours.

Saturday Night through Sunday: A second window for showers and
storms opens as low level moisture deepens & the mid-upper pattern
becomes more energetic. More precise details will clarify through
this week, though it does appear that periods of storms will be
around the region as the nose of the low level jet approaches and
ultimately folds over southern Wisconsin. Global ensemble
guidance is in relatively sound agreement regarding low level
jet evolution & placement, providing further confidence for
periods of storms during this time frame. A broad overlap of
sufficient shear and instability makes this a period to monitor
for organized/stronger thunderstorms, though whether these
parameters come together to realize any potential will depend on
smaller-scale features & timing not yet captured by available
guidance. Will be monitoring trends & providing additional info
as this portion of the period draws closer.

Quigley

&&

.AVIATION...
Issued 709 PM CDT Sun Aug 23 2026

Largely VFR conditions through the period. With skies clearing
this evening and winds diminishing, the one potential for lower
ceilings and visibilities will be with any fog that develops
after midnight. There is uncertainty in how widespread the
patchy fog could become, but visibilities could fall to around
2-4 SM. Terminals in low lying areas or river valleys (LNR and
JVL) will have the best potential for fog development. VFR
conditions are expected to return shortly after sunrise. Fair
weather cumulus clouds are expected to return late morning
through the evening Monday. The few to scattered cloud deck is
expected to be around 4-6 kft.

Light and variable winds tonight will become light northwesterly
winds Monday. A Lake breeze is expected to develop during the
early evening hours which will turn winds to the northeast then
east for lakeshore terminals. Light and variable winds are
expected again Monday night.

Patterson

&&

.MARINE...
Issued 1200 PM CDT Sun Aug 23 2026

Scattered shower chances continue over the northern third of Lake
Michigan this afternoon, with a few waterspouts possible. 1004 mb
low pressure is centered near the Ontario-Quebec border, resulting
in breezy northwest winds across the open waters of Lake Michigan.
The breezy winds will continue through tonight as the low lingers in
the same general vicinity. Expecting most gusts to remain in the 25-
30 knot range, though a few gusts approaching gale force are
possible over the northern third of the lake. Given the brief &
isolated nature of any such gusts, not anticipating the need for any
gale headlines, but will be monitoring trends. 1020 mb high pressure
will steadily build into the Upper Mississippi Valley today,
reaching the waters by Monday afternoon. The high`s arrival will
lead to decreasing winds, with conditions becoming light and
variable by Monday evening.

Light and variable winds will continue Monday night with high
pressure lingering in the vicinity. The high will shift east into
Ontario by Tuesday, resulting in a south-southwest wind shift across
the waters. 1005 mb low pressure will approach from the northern
Great Plains Tuesday night into Wednesday, reinforcing the south-
southwesterly wind pattern. The low will cross Lake Michigan during
the second half of the day Wednesday, bringing a breezy northwest
wind shift. Gales are not expected as this occurs. Showers and
thunderstorms will accompany the approaching/passing surface low
Tuesday night into Wednesday afternoon. It remains too early to tell
if any of these storms could be severe, with trends being monitored
through the beginning of this week. The next area of 1018 mb high
pressure will gradually build toward Lake Michigan from the northern
Great Plains Wednesday night through Friday, bringing slowly
decreasing winds.

A brief period of Small Craft Advisory conditions remains possible
Tuesday afternoon & evening ahead of approaching low pressure,
particularly to the north of North Point. Whether these conditions
will be sustained & widespread enough for headlines remains
uncertain at this time, with trends being monitored into tomorrow.
Showers and thunderstorms return to nearshore zones Tuesday night
into Wednesday along/ahead of an approaching cold front.

Quigley

&&

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

$$

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