NWS Milwaukee Forecast Discussion
018
FXUS63 KMKX 220852
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
352 AM CDT Tue Jul 22 2025
.KEY MESSAGES...
- High swim risks due to building waves and dangerous currents
for Ozaukee and Sheboygan County beaches today. Moderate swim
risk for Milwaukee and Racine County beaches as well.
- Scattered showers and storms will be possible tonight into
early Wednesday morning.
- Dangerous heat building into the state Wednesday and
Thursday. Heat indices of 100 to 107 degrees are expected. An
Extreme Heat Watch is in effect starting Wednesday.
- Increased shower and thunderstorm chances (>50%) for Thursday
with periodic chances Friday into Saturday.
&&
.SHORT TERM...
Issued 352 AM CDT Tue Jul 22 2025
Today through Wednesday:
Southeast winds will increase today as low pressure approaches
from the Northern Plains and high pressure holds steady over the
Upper Great Lakes. The steady winds over a long fetch will
produce high waves in the nearshore area and along the shoreline
of Ozaukee and Sheboygan counties. A high swim risk is expected
there today and a Beach Hazards Statement is in effect. Winds
will ease a little tonight and then ramp up out of the south on
Wednesday. Another high swim risk is expected north of
Milwaukee.
Today will be a transition day from our dry easterly flow to our
warm and moist southerly flow. The weather in southern WI will
remain dry today, although the cloud cover will be higher than
the previous days due to the low level moisture advection.
Dewpoints will rise into the lower 70s for western areas by late
afternoon.
The 00z models introduced a storm complex that should develop
along a remnant MCV as it drifts over central Iowa this
afternoon. There is remarkable model consensus that the storm
complex would drift into south central WI around midnight
tonight and weaken/diminish as it tracks through southern WI
overnight. Besides the forcing from the MCV, there is weak
synoptic support within the very southern edge of the low level
jet, warm air advection, and upper jet divergence. The 06Z run
of the NAM and NAMNest backed off the convective look a bit for
our area, so we will have to see how the 12Z models look.
Any established strong/severe storms upstream that track into
south central WI later tonight would have a brief potential for
gusty winds. The forcing drops off as the system would get into
southeast WI early Wednesday morning.
Wednesday temperatures may be in jeopardy if this system pans out
and brings extensive cloud cover for the first half of the day.
However, the robust area of heat and humidity will quickly push
into southern WI during the afternoon. Thus there is still
uncertainty and no need to make changes to the Extreme Heat
Watch that is in effect.
Cronce
Wednesday synopsis:
As broad surface high pressure continues to edge eastward into the
Atlantic Ocean on Wednesday, a surface pressure trough develops to
our west, spanning from Nebraska to central MN and northern WI.
The resulting southwesterly WAA will allow the upper level ridge
to continue to build, with daytime highs soaring to the low to mid
90s. The southwesterly surface flow is also expected to completely
wash out the lake breeze, spreading the heat to all areas.
Coupled with dewpoints in the mid 70s, maximum heat indices in
the 103 to 107 degree range are expected Wednesday.
Shortwave troughs riding the crest of the ridge are expected to
trigger thunderstorms along the surface pressure trough to our
north and west late Wednesday afternoon into Wednesday evening.
Our forecast features 15% precip chances in our northwest area
of counties (Sauk, Marquette, Green Lake) to account for the
off chance of these storms becoming progressive and moving off
of the surface pressure trough.
Sheppard
&&
.LONG TERM...
Issued 352 AM CDT Tue Jul 22 2025
Thursday through Monday:
The aforementioned surface pressure trough gradually sags
southward into Thursday, with continued southwest winds ahead of
it removing the lake breeze once again. This setup is expected
to allow the heat to remain in place Thursday, hence the Extreme
Heat Watch is allowed to continue. Thunderstorms are expected
to gradually evolve along the boundary as it sags southwards,
with slow / nearly stationary corfidi vectors and ECMWF and GFS
PWAT values just over 2 inches. Our best guess is for convection
to delay long enough to allow diurnal heating to run it`s
course (heat indices up to 105, with the highest potential
towards southeastern Wisconsin) followed by area-wide chances
for thunderstorms later Thursday afternoon into Thursday
evening. That said, the arrival times could change, and models
do resolve some PVA ahead of an approaching 500mb shortwave
arriving closer to mid- Thursday. The ingredients for a few
stronger thunderstorms and localized heavy rainfall are present,
more will become clearer on subsequent forecast iterations.
The surface pressure trough / baroclinic zone is expected to sag
further south (into Illinois) and dilute into Friday, resulting in
reduced (~30%) chances for showers and thunderstorms. Most models
drop the majority of QPF to the south of us on Friday, though
surface temp / dewpoint output on ensemble members do hint at the
possibility for remnant outflow boundaries or the sfc pressure
trough to waffle back northward, with a few showers /
thunderstorms to spare in our CWA. Partial cloud cover and
potential for a lake breeze should work together to slightly
reduce the heat on Friday, though the humidity should remain.
From a synoptic perspective, Saturday and Sunday are looking
relatively quiet (weak surface wind flow, some lake breeze
potential, not much of any upper-level dynamics to speak of),
though lingering warmth and humidity may be sufficient for airmass
thunderstorms, and models do keep the subtropical jet stream
close by, with some potential for a weak perturbation rippling
through (hence the broad-brushed 10-20% PoPs). A similar story
into Monday, with slightly higher chances of a perturbation in the
upper-level flow.
Sheppard
&&
.AVIATION...
Issued 352 AM CDT Tue Jul 22 2025
Dense fog developed at Sheboygan KSBM, but it seems localized
per satellite imagery. Patchy fog possible in other low lying
areas. Otherwise, there are pockets of stratus with VFR ceilings
of 4500 to 6000 ft early this morning, and this patchy stratus
could persist into the afternoon. There is also an area of MVFR
ceilings over eastern MN and northeast IA that may sneak into
southwest WI around midday before improving to VFR.
A thunderstorm complex may develop over Iowa this afternoon and
track across southern WI overnight while weakening.
Cronce
&&
.MARINE...
Issued 352 AM CDT Tue Jul 22 2025
Winds will increase to around 20 knots and veer southeast today
as low pressure approaches Minnesota from the Central Plains.
Breezy southerly winds up to 30 kt are expected Wednesday. There
is a Small Craft Advisory in effect for the daytime hours today
due to elevated waves with persistent southeast winds and large
fetch. Winds and waves will diminish a bit tonight, but increase
out of the south on Wednesday. Gusts up to 25 kt in the
nearshore north of Milwaukee seem probable and another Small
Craft Advisory should be needed.
There are chances for storms starting Wednesday morning and
continuing through Friday along a frontal boundary. Initially,
Wednesday into Thursday morning, expect the front to remain
stationary across the northern half of the lake. Thursday
afternoon through Friday, expect the front to push southward,
bringing storms southeastward through the remainder of the open
waters. A low pressure trough will drop through the area
Thursday night into Friday, shifting winds to westerly.
Cronce
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060...9 AM Tuesday to 7 PM
Tuesday.
LM...Small Craft Advisory...LMZ643-LMZ644...9 AM Tuesday to 7 PM
Tuesday.
&&
$$
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