NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 041918
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
218 PM CDT Tue Aug 4 2026
.KEY MESSAGES...
- Beach Hazards Statement in effect into this evening at
Sheboygan County beaches. Stay out of the water and away from
dangerous areas like piers and breakwalls!
- Periods of showers & storms expected this evening into
Wednesday afternoon. Heavy downpours will be the primary
impact in activity.
- Heat & humidity return Saturday-Tuesday, along with periods
of showers and storms.
&&
.SHORT TERM...
Issued 225 PM CDT Tue Aug 4 2026
Tonight through Thursday:
Synopsis/Mesoanalysis: A cold front is slowly across the state this
afternoon, with current obs showing the boundary extending along an
approximate Iron Mountain-Waupaca-Platteville axis. Rain with some
embedded thunder is ongoing along/behind the front from central Iowa
into eastern Nebraska. Activity is being encouraged by a combination
of surface-based & elevated processes, with boundary layer
frontogenesis being the primary driver in along-front precip &
overlapping warm advection and upper divergence being the main
forcing further west. Expect all of the aforementioned mechanisms to
migrate toward southern Wisconsin this evening & tonight as the cold
front continues east, with the end result being periods of showers &
embedded thunder. Precip will be ongoing within a seasonably moist
environment, which could lead to pockets of heavy downpours. While
not expected to be widespread, localized flooding impacts could
result, particularly over urban areas & in any locations
experiencing training. The currently approaching cold front is
expected to progress toward or just south of the Wisconsin-Illinois
border by Wednesday afternoon, with its precise location being
dependent on the evolution of evening/overnight precip. Should the
boundary linger around the Wisconsin side of the border, additional
scattered showers and storms would be possible Wednesday
afternoon-evening in south-central and southeast Wisconsin.
This Evening-Tonight: Beach Hazards Statement remains in effect
through 10 PM at Sheboygan County beaches. Will be watching showers
& embedded thunder move in from the southwest. General expectation
is for the leading edge of ongoing activity to move into areas west
of Madison between 430 & 600, the I-39 corridor between 600 & 800,
and the lakeshore between 800 & 1000. Will then see activity linger
off & on through the remainder of the overnight hours. Low overall
severe potential is trending even lower given expected arrival times
& increasing cloud cover ahead of the front, but will nevertheless
be watching for an isolated storm with some gusty winds immediately
along the front during the ~4-10 PM time frame. Elevated rainfall
rates remain the largest anticipated impact in activity given 1.5"+
precipitable waters pooled along & behind the front, with rainfall
rates being highest in embedded thunderstorms. Could thus see some
minor & localized flooding impacts in the event any embedded storms
linger over urban areas and/or train, though widespread potential is
low.
Wednesday: Have maintained ~40-50% precip probabilities into the
afternoon/evening primarily along/south of I-94 & US-18, where the
incoming front could stall in the wake of overnight showers/storms.
Higher probabilities will become necessary if it becomes clear that
the boundary will remain along/north of the Wisconsin-Illinois
border, and vice versa if it trends further south. Similar to this
evening/tonight, will need to watch for an isolated storm with gusty
winds & brief heavy downpours in the event more storm development
occurs. Collectively, generally expecting event-total rain in the
0.10-0.50" range across the north, with higher totals in the 0.50-
1.00" range approaching & moving south of I-94. Best potential for
training & locally higher totals to 2.00"+ will be near and south of
I-94 as well.
Quigley
&&
.LONG TERM...
Issued 225 PM CDT Tue Aug 4 2026
Thursday night through Tuesday:
High pressure will continue to build back into the region. No
significant weather is expected with low temperatures in the upper
50s inland and low 60s near the lakeshore. Winds will be light and
from the southeast.
By Friday winds will shift to be from the southwest ahead of the
next weak surface front to move through the region. Hot and humid
conditions return as high temperatures will peak around 80F and
dewpoint temperatures will top in the mid 60s. Expect lows Friday
night to be around the low/mid 60s. As the front moves through
Friday night, a stray shower or two may pop-up, but will be weak and
short lived (~15% chances).
Saturday morning will see rain chances diminish, but this will not
last long as low pressure from the Great Plains moves eastwards.
Several shortwaves will pass over the region starting Saturday night
which along with the heat and humidity (heat index near 90F) will
act as a starting point for showers and storms to return through the
end of the weekend (~30-50% chances) and into the beginning of next
week (~40-70% chances). Timing and severity of these storms remain
uncertain at this time, but will become clearer as the weekend nears.
Soergel
&&
.AVIATION...
Issued 225 PM CDT Tue Aug 4 2026
Scattered to broken diurnal cumulus clouds developed early this
afternoon. The ceiling bases are VFR, but there are some lower
scattered clouds mixed in with bases around 2800 ft AGL. A northwest-
to-southeast oriented front will slowly make its way through
southern WI tonight into Wednesday and it will be the focus for
showers and isolated thunderstorms.
The time period with the highest confidence to see a few
thunderstorms in southern WI will be during this evening. Then we
expect more widespread coverage of showers from late tonight into
Wednesday morning (much lower confidence in having any lightning).
With a lot of moisture in the atmosphere and the slow-moving system,
the showers will be efficient rain producers. Rain will diminish by
late morning, but a few showers are possible in the afternoon over
southeast WI.
MVFR ceilings are expected with the rain overnight into Wednesday,
and a period of IFR ceilings is possible during this time. Winds
will be light and variable starting this evening, but trending from
southwest today to northwest Wednesday.
Cronce
&&
.MARINE...
Issued 225 PM CDT Tue Aug 4 2026
1018 mb high pressure is centered between Lakes Erie and Ontario
this afternoon, resulting in generally southerly winds across the
open waters. A cold front is moving into western Wisconsin, and will
approach Lake Michigan through the remainder of the afternoon. The
front will slowly move across the waters this evening into Wednesday
morning, bringing a brief north-northwest wind shift. Periods of
showers and storms will accompany the slow-moving front, with severe
weather appearing unlikely at this time. Winds will trend variable
Wednesday evening through Thursday, when 1018 mb high pressure is
forecast to build back into the western Great Lakes.
A prolonged period of south-southwest winds will become established
across Lake Michigan Thursday night through Sunday as 1018 mb high
pressure lingers off the Mid-Atlantic coast and 1002 mb low pressure
stalls over the Hudson Bay. A slow-moving surface front will linger
across the western Great Lakes Saturday into the beginning of next
week, bringing multiple periods of showers and thunderstorms. Some
of these storms could be stronger, with additional details
clarifying through the end of this week.
Small Craft Advisory conditions continue into this evening from Port
Washington and points north, where a Small Craft Advisory remains in
effect through 10 PM CDT. The advisory may be canceled earlier than
the current 10 PM CDT expiration time if wave heights subside faster
than currently forecast, with trends being monitored through this
evening. Showers and thunderstorms are expected into tonight as a
cold front slowly moves through the region. Widespread severe
weather isn't expected, though a few storms could produce gusty
winds. Additional periods of storms are expected this weekend into
early next week as a front stalls over the western Great Lakes. Some
of these storms could be strong, with trends being monitored through
the rest of this week.
Quigley
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052 until 10 PM Tuesday.
LM...Small Craft Advisory...LMZ643 until 10 PM Tuesday.
&&
$$
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