501
FXUS63 KMKX 041527
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1027 AM CDT Fri Apr 4 2025

.KEY MESSAGES...

- Areas of rain move in late this afternoon through tonight.
  Best chances for precipitation are over south-central and
  southeastern Wisconsin.

- A quick round of snow will move across southern Wisconsin
  Sunday night into Monday morning, with minor impacts to the
  Monday morning commute possible in east-central and southeast
  Wisconsin.

- Below normal temps expected early next week, with highs
  rebounding to near & just above normal by mid-late week.

- The next disturbance approaches Wednesday through Thursday,
  bringing additional chances for rain to southern Wisconsin.

&&

.UPDATE...
Issued 1020 AM CDT Fri Apr 4 2025

The forecast remains largely on track today with clouds gradually
pushing in through the day with increasing chances for showers
across southern WI into the mid to late afternoon. CAMs do not
suggest much in the way of rainfall amounts but much of southern
WI should at least see a little rain. Some low level WAA and
some upper level PVA will be the primary forcing mechanisms for
this with increasing low to mid level moisture ushering in the
better potential this evening. While PWATs are actually pretty
decent for this time of year models do not show this to be a
very efficient rainfall producer.

Kuroski

&&

.SHORT TERM...
Issued 350 AM CDT Fri Apr 4 2025

Today through Saturday:

Synopsis/Mesoanalysis: 3 AM surface observations indicate an area of
1025 mb high pressure over northeast Wisconsin. Said high covers a
relatively extensive north-south portion of the state, with stations
from the Upper Peninsula border to as far south as the Wisconsin
River reporting clear skies and calm winds. Said combination of
clear skies and light winds has allowed for efficient radiational
cooling across most of the region, with most stations away from the
immediate Lake Michigan shoreline reporting temps in the upper 20s
and low 30s. Given the noted efficient surface cooling & similar dew
points in the upper 20s/low 30s, areas of patchy ground fog are
possible through daybreak, particularly in low-lying locations. With
temperatures at or below freezing, a few slick spots are possible in
any such areas of ground fog. An upper shortwave will quickly
progress from the southern Plains into the Ohio Valley tonight,
bringing chances for rain to all of southern Wisconsin. Appreciable
impacts are not anticipated in this round of rainfall. Rain is
expected to push out by mid-morning Saturday. Blustery northwest
winds & lingering cloud cover will lead to cooler highs in the upper
40s Saturday afternoon, with feel-like temps in the upper 30s.

Rest Of Tonight/Early This Morning: Can`t rule out some areas of
patchy ground fog through sunrise given efficient radiational
cooling & localized dew point depressions approaching zero. Forecast
soundings show an extremely shallow saturation layer at ground
level, with substantially drier air immediately above. Thus expect
the greatest potential for shallow/patchy ground fog in low-lying
spots susceptible to cold air drainage. Should any pockets of
localized ground fog form, isolated slick spots would be possible
given sub-freezing surface temps, particularly on bridges and
overpasses. Stay aware for brief drops in visibility and isolated
slick spots through the first half of the morning commute,
particularly away from the Lake Michigan shoreline.

This Afternoon Through Tonight: Mid-upper lift will increase across
southern Wisconsin as a shortwave trough moves into the Ohio River
Valley from the southern Plains. This lift will support rain chances
(40% or greater) areawide, with the greatest chances (~60% and
above) over south-central and southeast Wisconsin. Mesoscale
guidance and forecast soundings indicate that any MUCAPE will remain
well to the south of the area, making thunderstorm potential
negligible. Given the lack of thunder, don`t anticipate appreciable
impacts in tonight`s round of rainfall. Nevertheless, precipitable
water values are forecast to climb to/above 0.90" (~1 standard
deviation greater than early April norms) over southeast Wisconsin,
which could lead to some small responses in rivers/streams given the
rainfall occurring Tuesday and Wednesday. Any such responses are
likely to be minor, with probabilistic river forecast guidance
indicating 90-95% potential of all forecast points remaining below
minor flood stage.

Quigley

&&

.LONG TERM...
Issued 350 AM CDT Fri Apr 4 2025

Saturday night through Thursday:

Synopsis: Temperatures will be a touch milder Sunday afternoon under
partly to mostly sunny skies. An upper disturbance will quickly
progress from western Ontario to southern Lake Michigan Sunday night
through Monday. The upper wave will be accompanied by low pressure
at the surface, which track near or just to the east of Lake
Michigan. A cold front attendant to the surface low will sweep
across southern Wisconsin Sunday night into early Monday morning.
Combined lift from the encroaching upper disturbance & surface cold
front will support a quick round of snow Sunday night into Monday
morning, with the best chances (~30-40%) being over the eastern half
of the region. Light accumulations are forecast in this round of
snow, particularly in east-central and southeastern Wisconsin. Given
the timing of snow, minor impacts to the Monday morning commute
can`t be ruled out in east-central and southeastern Wisconsin. Gusty
north-northwest winds will become established behind the departing
cold front Monday afternoon, holding temperatures in the upper 30s &
feel-like temps near/below freezing. Below-normal temps will persist
through Tuesday as high pressure moves across the western Great
Lakes. Winds will turn southerly and eventually southwesterly
Wednesday-Thursday, allowing temps to climb back to or just above
normal. The next upper disturbance & surface front will approach
late Wednesday into Thursday, bringing the next chances for rainfall
to southern Wisconsin.

Sunday Night Into Monday Morning: A quick round of snow is forecast
across southern Wisconsin. Greatest chances for snow will be over
the eastern half of the area, where proximity to the passing upper
disturbance will be greatest. Medium range guidance shows a
combination of mid-level DPVA & pronounced 1000-850 mb FGEN over the
eastern half of the area, promoting saturation and ascent within the
DGZ. Favorable dynamics & thermo within the DGZ, combined with
signals for weak CSI within the cold frontal/CAA regime, point
toward the potential for elevated (0.5"+/hr) hourly snowfall rates
as precip moves across the region. Residence time of these rates
will be limited given the fast-moving nature of the surface cold
front, though their presence could support light accumulations
across east-central and southeastern Wisconsin. Initial
probabilistic guidance indicates medium-high (~40-70%) potential for
at least 0.1" of accumulation over this part of the area, with low
(~10-30%) potential for over 1". Given the timing of the snow &
embedded higher rates, can`t rule out some minor impacts to the
Monday morning commute in east-central and southeastern Wisconsin.
Will be watching trends closely in the coming forecasts.

Wednesday Through Thursday: The next disturbance and surface front
will approach from the Plains, bringing additional precip chances to
southern Wisconsin. Milder temperatures point toward all rain at
this time, with trends being monitored as this part of the period
draws closer.

Quigley

&&

.AVIATION...
Issued 1025 AM CDT Fri Apr 4 2025

Light winds from the east today ahead of a system expected to
bring in rain showers beginning in the south to southeast parts
of southern WI by the mid to late afternoon. Into the evening
chances will increase across southern WI especially as better
low level moisture pushes in. This will allow for CIGS to fall
to MVFR across much of southern WI with at least parts of
southeast WI seeing the potential for some IFR CIGS. Low CIGS
will continue through Saturday morning before pushing out
Saturday afternoon as we clear out from the west. Limited VSBY
concerns given largely light rain showers expected tonight but
MVFR VSBYs will remain possible with any showers. Shower
potential will end across southern WI by 12z Saturday but likely
earlier the further west you go. Otherwise winds will turn back
to the northwest overnight into Saturday morning.

Kuroski

&&

.MARINE...
Issued 350 AM CDT Fri Apr 4 2025

1022 mb high pressure is centered over the western Great Lakes early
this morning, resulting in light winds across the open waters. Said
high will quickly progress east into Ontario today, allowing
northeast surface winds to become established over the entirety of
Lake Michigan. Said winds will increase overnight tonight as 1010 mb
low pressure develops in the middle Mississippi River Valley,
particularly across the southern half of the open waters. Gusts up
to 20 knots will be possible during this time frame. Breezy
conditions will continue into the day on Saturday as the
aforementioned surface low quickly moves across Lakes Erie and
Ontario. This progression will allow winds to turn out of the north-
northwest by early Saturday afternoon. Winds will taper slightly
Saturday night, when 1020 mb high pressure will build into the
northern Great Plains.

Winds will briefly shift out of the south-southwest during the day
on Sunday, when low pressure of 1012 mb is forecast to develop over
east-central Ontario. The low will progress south Sunday evening as
it deepens to near 1010 mb, passing near or just east of the open
waters by Monday morning. Winds will shift out of the north to
northwest behind the departed surface low on Monday, becoming gusty
by late morning. Widespread gusts between 25-30 knots are forecast
through Monday afternoon, with a few gusts up to gale force
possible. Trends will be monitored in the coming forecasts for
possible headlines. Gusts will taper Monday night as 1022 mb high
pressure moves into the western Great Lakes.

In nearshore zones, north-northwest wind gusts and elevated wave
heights will approach & likely exceed Small Craft Advisory
thresholds through most of the day on Monday. Headlines will likely
become necessary in later forecasts. Winds and waves will decrease
by early Tuesday morning as high pressure builds into the Upper
Midwest.

Quigley

&&

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

$$

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