729
FXUS63 KMKX 101956
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
256 PM CDT Thu Jul 10 2025

.KEY MESSAGES...

- Showers and storms are likely (50-70%) later this afternoon
  through tonight. A few storms may be strong to severe this
  afternoon and evening mainly west of I-41. There will be a
  heavy rainfall threat tonight into early Friday, mainly along
  and south of I-94.

- Active weather continues Friday into Saturday, with additional
  periods of showers and storms likely (50-70%). Locally heavy
  rainfall and a few stronger storms will be possible again.

- Mostly dry conditions are likely Sunday through at least early
  Tuesday, with shower/storm chances returning later Tuesday or
  Wednesday.

&&

.SHORT TERM...
Issued 255 PM CDT Thu Jul 10 2025

Tonight and Friday:

An area of showers continues to move in from the west this
afternoon, as a remnant MCV from overnight convection gradually
approaches. Thunderstorms are expected to redevelop in the
vicinity of the MCV by late this afternoon, likely within an
area of clearing where instability is higher. A few strong to
severe storms will be possible, particulary west of I-90, given
the instability along with shear that is likely being enhanced
by the MCV. Large hail, damaging winds, and even a brief tornado
will be possible if storms are able to get going this
afternoon. Storms may struggle to hold together as they head
east of I-90 given lower dewpoints and a generally more stable
environment with onshore winds.

Attention then turns to a heavy rainfall threat tonight into
early Friday. Models show persistent warm air and moisture
advection during this period, with a weak frontal boundary
generally stalled in the area. Precipitable water values will be
pushing 2 inches tonight into Friday and storm motion will
likely be on the slower side, with repeated rounds of storms
possible along the boundary. There is some uncertainty with
where this swath of heavier rain will set up, with a couple of
the latest mesoscale models shifting a bit southward. Generally
2 rows of counties north and south of the IL/WI border have the
highest chance to seeing the heaviest rain, with the picture
hopefully becoming a bit more clear over the next few hours.

There may be a lull in widespread precip mid Friday morning into
early afternoon, with a chance storms then develop along the
residual boundary by mid or late afternoon. Looks like enough
shear and instability for a severe threat again, with locally
heavy rainfall also possible. Not the highest confidence in high
temps tomorrow given uncertainty with how long clouds will
linger. Overall though, looks like highs within a couple
degrees of normal.

DDV

&&

.LONG TERM...
Issued 255 PM CDT Thu Jul 10 2025

Friday night through Thursday:

Stalled frontal boundary with southwesterly WAA from the surface
through 700 mb pointed into southern Wisconsin and Lake Michigan
by Friday night. Current trends are towards a semi-stationary
line of rain and thunderstorms across far southern Wisconsin,
although a significant amount of variability remains. NAM and Euro
indicate a more northern extent to the LLJ at 850 mb, keeping
convection alive across central to southern Wisconsin. This more
northern solution is dependent on phasing between a more well-
defined low pressure system traversing the southern Canadian
Prairies overnight and the remaining warm frontal feature from a
developing Colorado High Plains low. As the cold front from the
northern low approaches, phasing between the 500 mb waves would
allow for a stronger push of convective initiation across more of
southern Wisconsin. Regardless of exact placement of the frontal
boundaries and the amount of interaction between the two systems,
modeling is in firm agreement that PWATs of 1.75 to 2 inches will
be available to developing storms, in a deep warm cloud layer
environment. This will lead to high precipitation efficiency in
storms that do develop and enhance the heavy rainfall threat. The
main question that remains is the exact location of this axis of
precipitation. Therefore kept 40 to 60 percent chance PoPs in the
forecast for now. Confidence is high that storms will develop, but
low in placement. Will refine as the system develops and
confidence increases.

Saturday, high confidence in the northern low pressure system over
southwestern Ontario, bringing a neutral to negatively tilted
trough through northern to central Wisconsin. Unzipping along the
cold front into the lingering warm frontal boundary is also
possible as the weak low pressure in the High Plains ejects into
the central Plains through the day Saturday. Main questions for
southern Wisconsin remain forcing and CAPE. Primary 500 mb
shortwave remains to the north, with weak PVA across southern
Wisconsin from the lingering warm frontal boundary. 0 to 6 km bulk
shear values only around 20 to 30 kt, with the strongest shear
across central Wisconsin, and afternoon MUCAPE values between 1500
and 2000 J/kg. This favors primarily wet microbursts and perhaps a
few stronger storms capable of producing small hail. However,
morning overrunning precipitation may keep MUCAPE values lower for
the afternoon when the 500 mb trough makes its closest approach.
In addition, the surface cold front looks to lag behind the 500 mb
trough. If this front comes through later in the evening,
stronger storms become much less likely. All that said,
thunderstorms are likely (50 to 70 percent chance) during the
afternoon hours with multiple potential lifting mechanisms in
play.

Precipitation ends into Saturday night as the final cold frontal
push moves offshore into Lake Michigan, with northwesterly flow
bringing in dry conditions overnight into Sunday. Weak southerly
flow returns by Monday as low pressure develops in the northern
High Plains and ridging builds across the Plains into the Upper
Midwest. Temperatures may rise as high as 90 degrees Monday into
Tuesday as ridging builds, with scattered thunderstorms possible
within the warm and moist airmass (20 to 30 percent chance). Heat
index values currently expected in the lower 90s, but trends will
be monitored for high heat conditions. Chances increase (40 to 60
percent chance) into Wednesday as low pressure ejects eastward
and brings next major system to Wisconsin. Modeling in decent
agreement that this system will continue into the eastern Great
Lakes by Thursday night, but wrap around showers and storms remain
possible into Thursday (15 to 40 percent chance, highest in the
east).

MH

&&

.AVIATION...
Issued 255 PM CDT Thu Jul 10 2025

Showers and storms are expected to develop mainly southwest of
I-90 by later this afternoon. Storms will advect eastward, but
may struggle to hold together as they approach the lake.
Additional rounds of showers and storms are likely tonight into
early Friday and then possibly again Friday afternoon. There is
less confidence with the swath of the more widespread storms
tonight, with models varying across a couple rows of counties
north and south of the IL/WI border. A few storms may be strong
to severe this afternoon and evening, with heavy rainfall a
concern tonight into early Friday.

Light south to southeast winds will persist through tonight,
remaining more easterly near the lake this afternoon as a lake
breeze pushes in. Southerly winds will pick up a bit Friday
ahead of an approaching trough.

VFR conditions will largely persist through Friday, though
models do show a potential period of lower ceilings late tonight
into early Friday. Lower ceilings and visibilities will also be
possible within any heavier rainfall.

DDV

&&

.MARINE...
Issued 255 PM CDT Thu Jul 10 2025

High pressure of 30.0 inches overhead this afternoon will
gradually slide eastward tonight into Friday as a broad trough
of 29.8 inches slowly approaches from the west. Winds will
remain light and somewhat variable into tonight, becoming
southerly by Friday morning between the departing high and
approaching low. Winds will pick a bit out of the south on
Saturday as the trough nears, becoming westerly Saturday night
behind the trough.

Rounds of showers and thunderstorms are likely this evening
through tonight, mainly across the south half of the lake.
Shower and storm chances will then continue Friday night and
Saturday across the lake.

DDV

&&

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

$$

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