137
FXUS63 KMKX 270241 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
941 PM CDT Thu Jun 26 2025

.KEY MESSAGES...

- Thunderstorms will continue to weaken as they track across
  southern and central WI late this evening and into the early
  overnight hours.

- Somewhat cooler and relatively quiet weather expected Friday
  and Saturday, before temperatures turn much warmer/more humid
  on Sunday.

- A cold front Sunday night will bring temperatures back to
  around average for much of next week.

&&

.UPDATE...
Issued 941 PM CDT Thu Jun 26 2025

After a long afternoon of scattered showers and thunderstorms
firing within an area with no cap (west of the lake breeze) but
no upper forcing, we are transitioning into seeing the line of
storms arrive along a pre-frontal trough. There is one stronger
segment of storms that moved into south central WI over the past
hour and we are warning on it due to wind. That area has not
been touched by the lake breeze, but is notchy and has some
marginally favorable shear for qlcs tornado, thus we have keep
the tor possible tag in the warning.

The southern part of the line is showing signs of gusting
out/weakening, and the northern part is moving into the air mass
stabilized by the lake breeze. There is still a question if the
thunderstorms will hold together all the way to Lake Michigan,
of if there will just be scattered showers by then, or if
everything will dissipate before reaching the lake especially
toward southeast WI. Milwaukee has been socked into the marine
layer with a northeast breeze and ceilings of 500 feet, so
stability is very high there.

With the front lagging behind the storms overnight, there is a
chance for showers through mid Tuesday morning. Thunderstorms
look very unlikely.

Cronce

&&

.SHORT TERM...
Issued 243 PM CDT Thu Jun 26 2025

Rest of this Afternoon through Tomorrow:

Main focus for this afternoon and evening will be severe weather
potential. As of 2 PM, a warm front stretched across south
central Wisconsin, generally just north of the I-94/US 18
corridor, curving back southeastward near Lake Michigan. As low
pressure along the Iowa/Minnesota state line moves east-
northeastward, this warm front will continue to slowly move
northward. Convection should expand along the warm front this
afternoon, though the spatial extent is still in question given
the relatively weak lift. That said, anything that becomes
rooted in the boundary layer will have a very unstable airmass
to work with, with MLCAPE in excess of 2000 J/KG. There is also
a substantial amount of low level CAPE, with 0-3 KM values
between 100 and 200 J/KG.

While Low level shear isn`t terribly impressive, the strong low
level instability and localized increase in helicity associated
with the warm front may be sufficient for a tornado threat with
this afternoon`s convection, along with a few strong wind
gusts. Weak mid level lapse rates and high freezing levels
suggest that while a few instances of severe hail are possible,
it should not be widespread.

Later this evening focus will then shift to a line of storms
moving in from the west. These will be more likely to contain
damaging wind gusts compared to the afternoon convection, along
with a somewhat lower tornado threat. Any eastward surges in the
line, especially if collocated with the warm front or an
outflow boundary, will still pose a risk for QLCS circulations,
however.

Storms will gradually weaken with eastward extent this evening, with
the severe weather risk expected to largely dissipate by
midnight. A few showers may linger into Friday morning, but
otherwise most of the day on Friday should be dry. Highs
tomorrow will be cooler, with upper 70s to around 80 expected.
Winds will turn more northwesterly by afternoon helping to usher
some lower dewpoints into the region as well.

Boxell

&&

.LONG TERM...
Issued 243 PM CDT Thu Jun 26 2025

Tomorrow Night through Thursday:

High pressure will sink south into the region late tomorrow
night, setting the stage for what should be a fairly pleasant
Saturday. Highs Saturday will range from the low to mid 80s,
warmest southwest of Madison, with dewpoints in the low to mid
60s. A few showers or thunderstorms will be possible on Saturday
near the state line, as a shortwave ripples through.
Thunderstorm chances then increase area-wide late Saturday night
and especially Sunday as a cold front sharpens to the northwest.
This looks to pass through the area Sunday night, with an
associated increase in PoPs through the afternoon and evening
hours Sunday. Ahead of the front, a very warm and humid day is
expected, with highs Sunday around 90. A Heat Advisory may
eventually be needed for parts of the area, as heat indices will
top out around 100.

A few days of northwest flow will bring highs back to more
average values, with highs in the low to mid 80s, and overnight
lows in the low 60s. Dewpoints are also looking more tolerable,
with values in the low to mid 60s most days.

Boxell

&&

.AVIATION...
Issued 941 PM CDT Thu Jun 26 2025

Expect a temporary reprieve from the IFR ceilings near the lake
as the lower atmosphere gets stirred up due to outflow
boundaries. Then MVFR to IFR ceilings should settle back into
lakeshore areas overnight after the prefrontal trough clears.
Intermittent showers are possible overnight through mid Tuesday
morning until the main front clears southeast WI.

Expect westerly winds with gusts up to 20 kt behind the front
from mid Tuesday morning through mid Tuesday afternoon with
increasing ceilings through noon and clouds slowly scattering
during the afternoon.

Cronce

&&

.MARINE...
Issued 243 PM CDT Thu Jun 26 2025

Low pressure of 29.8 inches will move across the Iowa and
Minnesota border today, reaching Wisconsin tonight. A stationary
front will stay parked over the southern end of the lake into this
evening with southerly winds south of the boundary and north to
northeast winds north of the boundary. As the surface low
approaches tonight, winds will come around to southwesterly over
the whole lake and thunderstorms are expected over much of the
open waters. The low is then expected to pass early Friday
morning, dragging a cold front over the lake. Winds will become
westerly and northwesterly early Friday, becoming northerly
Friday night as high pressure of 30.0 inches moves through the
area.

Winds return to a southeasterly to southerly direction Sunday as
the high moves east of the region.

Boxell

&&

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

$$

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