NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 222234 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
534 PM CDT Sat Aug 22 2026

.KEY MESSAGES...

- Scattered showers & thunderstorms over east-central and
  southeast Wisconsin through early this evening. A few storms
  could produce gusty winds to 40 MPH.

- An isolated waterspout or two are possible over Lake Michigan
  through tonight.

- Dry and pleasant conditions into the beginning of next week.
  Storm chances return Tuesday evening into Wednesday.


&&

.UPDATE...
Issued 534 PM CDT Sat Aug 22 2026

Scattered showers and storms in the east due to a weak wave and
lake breeze interaction will continue into early evening.
Activity is expected to wind down quickly though as daytime
heating is lost. Mostly clear skies, light winds, and decreasing
dewpoints are then expected tonight as high pressure builds in,
with lows a few degrees below normal around the low 50s most
places.


DDV

&&

.SHORT TERM...
Issued 1145 AM CDT Sat Aug 22 2026

This afternoon through Sunday night:

Synopsis/Mesoanalysis: Fair weather cumulus are developing late this
morning as surface heating commences within modest low level
moisture still in place. While subtle, 11 AM surface observations
identify a weak surface boundary extending from near Green Bay west
toward the Black River Falls vicinity. Modest north-south moisture
differences, in addition to slight cyclonic surface convergence,
have been noted across the boundary through the late morning hours.
Anticipate that this surface front will continue to sag south into
east-central and southeast Wisconsin this afternoon, with its
affiliated surface convergence providing just enough lift for
scattered showers and thundershowers mainly along/east of a Ripon-
Lake Mills-Lake Geneva line. Not expecting much in the way of
hazards in any activity, although the strongest thundershowers could
produce a few cloud to ground lightning strikes and wind gusts to 40
MPH. Keep an eye on the sky if planning to be outdoors across the
east this afternoon. Currently centered along the North Dakota-
Manitoba border, high pressure will gradually shift into the Upper
Mississippi Valley tonight, ultimately moving overhead on Sunday
night. The high's approach & arrival will maintain a Canadian air
mass across southern Wisconsin tonight through Sunday night, leading
to fall-like conditions during the overnight periods.

This Afternoon: Monitoring for a gradual increase in
shower/thundershower coverage across the east as a weak surface
boundary works in from the north. Expect that most activity will
generate as the aforementioned boundary impinges upon the more
focused area of cumulus clouds currently evident from Ripon-
Sheboygan south to Burlington-Milwaukee. Have thus continued 20-40%
precip probabilities along & east of a Ripon-Lake Mills-Lake Geneva
line in the mid-day update. Severe weather threat is low in any
development given modest instability & weaker along-boundary
convergence, though steep low level lapse rates & deeply mixed
boundary layers could support isolated wind gusts to 40 MPH in any
collapsing precip cores. A few cloud to ground lightning strikes are
possible as well. Keep an eye on the radar if planning to be
outdoors across the east this afternoon.

Quigley

&&

.LONG TERM...
Issued 1145 AM CDT Sat Aug 22 2026

Monday through Saturday:

Synopsis: High pressure will continue across the state on Monday,
leading to plentiful sunshine & continued dry conditions with low
humidity. The high will 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.
Disagreement amongst global guidance regarding the timing of the
forcing mechanisms casts some uncertainty over how many rounds of
storm development will occur, in addition to storm intensity. Trends
will be monitored over coming forecasts. 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.

Tuesday Evening through Wednesday: The best thunderstorm chances of
the long term period enter the forecast ahead of an upper wave and
cold front. Current blended & ensemble guidance generally points to
a warm sector spreading into the area Tuesday evening/night, with
the trailing cold front then pushing through at some point during
the day Wednesday. Precip forecasts from the NBM thus like the idea
of an initial batch of storm development within the warm advection
regime Tuesday evening/night, followed by additional development
along the passing cold front at some point on Wednesday. Available
deterministic guidance, however, muddies this picture, with a number
of different scenarios being depicted regarding the evolution of
both the surface pattern & flow aloft. Have thus trended the precip
forecast toward the blended/ensemble scenario at this point, with
the understanding that some changes are likely to occur into early
next week given the noted range of solutions in the deterministic
suite. Aforementioned questions regarding the extent and quality of
the warm sector make the potential for any strong/severe storms
unclear in this forecast, though prevailing deep layer shear would
be sufficient for at least some storm organization in the event
timing & spacing allowed for enough destabilization. Will be
monitoring trends and providing more details as this portion of the
period draws closer.

Quigley

&&

.AVIATION...
Issued 534 PM CDT Sat Aug 22 2026

Scattered showers and storms in the east due to a weak wave and
lake breeze interaction will continue into early evening.
Activity is expected to wind down quickly though as daytime
heating is lost. Winds will waffle between northeast and
northwest toward Lake Michigan, as the lake breeze stalls though
early evening. Mostly clear skies and light winds are then
expected tonight into early Sunday as high pressure builds in.
Scattered VFR cumulus and modest northwest winds are likely late
Sunday morning into the afternoon.

DDV

&&

.MARINE...
Issued 1145 AM CDT Sat Aug 22 2026

1010 mb low pressure is centered over the southern Hudson Bay this
morning, resulting in generally northeast winds across the open
waters of Lake Michigan. These winds will continue into this evening
as a weak cold front moves across the lake and 1023 mb high pressure
builds into the northern Great Plains. Isolated showers and
thunderstorms are possible along the passing front this afternoon &
evening. Severe weather potential is low in this activity, though an
isolated stronger storm with gusty winds or a waterspout can't be
entirely ruled out. Will be watching radar trends for any potential
marine weather statements or special marine warnings through this
evening. Northwest winds will continue through the day Sunday,
ultimately weakening by Sunday night as the aforementioned area of
high pressure approaches Lake Michigan.

Light and variable winds will continue Monday 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 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
into the beginning of next week.

Scattered showers and thunderstorms are possible in nearshore zones
this afternoon as a weak cold front moves south across Lake
Michigan. An isolated stronger storm with gusty winds or an isolated
waterspout can't be entirely ruled out. Increasing southerly winds
and wave heights may lead to a brief period of Small Craft Advisory
conditions Tuesday afternoon & evening, particularly to the north of
Milwaukee. Will be monitoring trends & evaluating the need for any
headlines through the beginning of next week. The next thunderstorm
chances arrive Tuesday evening through Wednesday, with severe
weather potential uncertain at this time.

Quigley

&&

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

$$

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