NWS-Milwaukee/Sullivan Forecast Discussion
FXUS63 KMKX 220421
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1121 PM CDT Tue Jul 21 2026
.KEY MESSAGES...
- Beach Hazards Statement remains in effect through 7 AM
Wednesday in Sheboygan & Ozaukee Counties & 1 PM Wednesday
from Milwaukee County south to the state line.
- Dry & less humid through the rest of the work week. Muggy conditions
return this weekend.
- Showers & storms return to the forecast Saturday night into
the beginning of next week.
&&
.SHORT TERM...
Issued 1125 PM CDT Tue Jul 21 2026
Rest of Overnight through Thursday:
Synopsis/Mesoanalysis: Earlier afternoon & evening rain showers have
dissipated post-sunset over east-central and southeast Wisconsin.
Broken cloud cover remains over the region, with surface obs showing
a secondary cold front continuing to progress south across southern
Wisconsin. Forward progress of the front was significantly quicker
over the open waters of Lake Michigan, resulting in a faster
boundary arrival & subsequent temperature drop in lakeshore
communities earlier in the evening. The front will move through the
rest of the area through the remainder of the overnight, allowing a
cool Canadian air mass to settle in by daybreak. Arrival of the air
mass will bring some of the coolest overnight lows since mid-late
June tonight and Wednesday night. Currently centered along the North
Dakota-Manitoba border, high pressure will build southeast into the
western Great Lakes through the period, maintaining precip-free
conditions and plenty of sunshine.
Rest of Overnight through Wednesday morning: With winds remaining
elevated behind the departing surface front/ahead of the building
surface high, elevated wave heights will persist at Lake Michigan
beaches. Moderate to high swimming risk conditions will thus continue
through mid-day Wednesday, with Beach Hazards Statements remaining
in effect for all Lake Michigan counties. With high pressure
building in, winds (and thus wave heights) will taper from north to
south by early Wednesday afternoon. Thus not anticipating any
changes to Beach Hazards Statement end times (7 AM Sheboygan/Ozaukee
Cos; 1 PM Milwaukee/Racine/Kenosha Cos), but will nevertheless
continue to monitor trends. Exercise extreme caution if heading
lakeside through Wednesday morning.
Quigley
&&
.LONG TERM...
Issued 1125 PM CDT Tue Jul 21 2026
Thursday night through Monday:
Synopsis: Upper level ridging will persist over the western CONUS
through the period, with west-northwest upper level winds expected
across the western Great Lakes. High pressure will shift east Friday
into Saturday, allowing for southerly winds and steadily climbing
surface temperatures through the weekend. Increasing humidity will
eventually accompany the rising temperatures, though its arrival
will lag behind that of the warmer air temperatures. Expect that
deeper humidity will make it back into the area later Saturday. Low
pressure is progged to move quickly from the Canadian Prairies
Friday into Saturday, pulling a cold front into the western Great
Lakes. The boundary is forecast to slowly advance southward through
the area Saturday night through Monday, with medium range guidance
split over the speed of its progression. With the slow-moving front
impinging on the newly-arrived more humid air, periods of showers
and thunderstorms return to the forecast from Saturday night into
Monday. The aforementioned uncertainties regarding frontal
progression lead to low forecast confidence in preferred storm
timing & corridors at this time, with details coming into view as
trends clarify through the remainder of this week.
Saturday through Monday: Continues to appear that the most
noteworthy weather of the entire forecast period will occur during
this time frame, with returning heat/humidity & a slow-moving
surface front leading to elevated (90+ degF) heat indices and storm
chances. Trends continue to point toward heat indices staying just
below advisory thresholds, with the latest statistical guidance
holding most > 50% probabilities of 100 degF heat indices to the
west-southwest of the area. Will continue to be watching for any
upward trends. Blended solution of the NBM currently favors a Sunday
afternoon & night timing for storms, implying that southern
Wisconsin will remain too capped for convection Saturday/Saturday
night & that the responsible frontal boundary will be too far south
of the area to support additional development on Monday. Quick
comparison of individual ensemble & deterministic solutions,
however, makes it clear that this timeline could shift with changes
in frontal speed, mesoscale influences, or both. Thus anticipate
some additional shifts in the timing forecasts for the peak precip
window(s) through the second half of this week. Raw overlap of
modeled instability, shear & precipitable water implies that there
could be some potential for strong/severe storms with heavy
downpours, though the aforementioned uncertainties make it difficult
to offer additional details at this time. Will continue to provide
updates as trends clarify.
Quigley
&&
.AVIATION...
Issued 1125 PM CDT Tue Jul 21 2026
Mainly VFR flight categories prevail late this evening across the
region, with the exception of far southeast Wisconsin where BKN CIGs
between FL025 and FL030 continue to linger behind an evening frontal
passage/intrusion of marine air from Lake Michigan. Have extended
the prior TEMPO MVFR groups at KMKE and KENW given trends, with the
expectation still being for larger scale flow to scour out marine
air and lingering low CIGs through the predawn hours. Will continue
to monitor trends. High pressure will gradually build in from the
Northern Plains through the remainder of the period, allowing for
gradual weakening of surface winds beneath areas of FEW to SCT
clouds based between FL150 and FL250.
Quigley
&&
.MARINE...
Issued 1125 PM CDT Tue Jul 21 2026
Gusty north winds continue late this evening across the open waters
behind a departing cold front. Gusts are expected to remain at or
below 30 kts across the majority of the lake, though a few gusts
approaching gale force remain possible through the predawn hours
over the northeast half of the waters. Winds will steadily subside
through the day Wednesday as 1020 mb high pressure builds into the
northern Mississippi River Valley from the Great Plains. The high
will cross southern Lake Michigan Thursday morning, progressing into
the northeastern United States Thursday night into Friday.
Progression of the high will result in a south to southwest wind
shift across the waters.
998 mb low pressure will move quickly from the Canadian Great Plains
toward Quebec Friday through Saturday, maintaining south to
southwest winds over Lake Michigan. The low will attempt to pull a
cold front into the western Great Lakes by Sunday, with the boundary
slowly advancing south across the waters through Monday. The
approaching/passing front will result in returning thunderstorm
chances Saturday night through Monday, in addition to a northerly
wind shift by Monday afternoon.
Elevated winds and wave heights will linger into Wednesday afternoon
in nearshore zones. Small Craft Advisories remain in effect through
7 AM CDT Wednesday morning from North Point north to Sheboygan, and
until 4 PM CDT Wednesday afternoon from North Point south to
Winthrop Harbor. Will be monitoring for additional periods of Small
Craft Advisory conditions Friday into the weekend as high pressure
shifts east and a cold front attempts to work into the western Great
Lakes. Shower and thunderstorm chances return late Saturday night
into Monday ahead of the front.
Quigley
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ066-WIZ071-WIZ072 until 1 PM
Wednesday.
Beach Hazards Statement...WIZ052-WIZ060 until 7 AM Wednesday.
LM...Small Craft Advisory...LMZ643-LMZ644 until 7 AM Wednesday.
Small Craft Advisory...LMZ645-LMZ646 until 4 PM Wednesday.
&&
$$
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