NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 090942
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
442 AM CDT Wed Sep 9 2026

.KEY MESSAGES...

- Showers with isolated embedded thunderstorms remain possible
  this morning, dry weather and decreasing clouds from midday
  onwards.

- Warm temperatures with low humidity through the second half of
  the work week.

- Next chances for storms develop late Friday night into
  Saturday morning, and again Sunday into Monday.

&&

.UPDATE...
Issued 440 AM CDT Wed Sep 9 2026

As I write this, the radar is currently clear over southern WI,
with GOES Nighttime Microphysics satellite imagery showing some
attempted (but mostly failed) elevated convective initiation
over the past few hours along a La Crosse to Green Bay line,
co-located with the leading edge of the 925-850mb LLJ.

Despite the apparent lack of precip on the radar, we may yet see
some scattered development overhead (as shown on intermediate
CAM runs) between now and late this morning, driven by MUCAPE
and continued LLJ activity. Instability with it would be fairly
limited, only 500 joules MUCAPE or locally higher. This would
allow for showers with briefly heavy rainfall and a few rumbles
of thunder, but that's just about it.

Drier air will begin to advect into the region behind a cold
front midday, quickly bringing an end to the precip chances and
gradually reducing cloud cover through the afternoon today.

Sheppard

&&

.SHORT TERM...
Issued 129 AM CDT Wed Sep 9 2026

Today through Thursday night:

Rain with isolated embedded thunderstorms will continue across
far southern Wisconsin, with minimal impacts expected.
Additional storms are in the process of developing along the
nose of the LLJ in central Wisconsin, and are expected to
progress gradually southeastward through southern Wisconsin
through this morning. Lightning is expected to be the main
hazard with this activity, but heavy rain is also possible due
to continued high PWATs in the 1.5 to 2 inch range. However, any
heavy rain impacts would be dependent on multiple storms moving
over the same area. Storms will taper off into the early morning
hours and become another area of light rain as the LLJ shuts
off. Showers and rain then end north to south by mid-morning.

High pressure returns to the area this afternoon, bringing
clearing skies and northwesterly winds. Expect highs in the
upper 70s to low 80s. Winds gradually diminish through the
evening, with mostly clear skies and light and variable winds
overnight tonight. Expect lows in the mid 50s to near 60
degrees.

High pressure propagates overhead Thursday into Thursday night,
with continued light and variable winds, highs in the 70s, and
lows in the 50s.

MH

&&

.LONG TERM...
Issued 129 AM CDT Wed Sep 9 2026

Friday through Monday:

Friday and Friday evening will be dry now, as the forecast has
trended drier each day. This is due to high pressure remaining in
place over the lower Great Lakes longer. Low pressure developing
over the Dakotas on Friday will lift into northern MN. We can
expect increasing southerly winds in southern WI, along with an
uptick in temperatures and dewpoints (upper 70s/lower 60s).

The strongest forcing will be over Upper Michigan as the low
tracks overhead and the low level jet focuses there. The other
area of forcing will arrive with a mid level shortwave trough
tracking from the central Plains to IA and northern IL late
Friday night through Saturday morning. There are hints from the
models that the precip associated with these two forcing areas
will split right around southern WI.

Winds will shift to the west Saturday afternoon behind the surface
trough, but gusts will be less than 20 mph. Saturday will be our
warmest and most humid day with highs closer to 80 and dewpoints
potentially pooling ahead of the trough/cold front to values in
the upper 60s. Temperatures will fall into the 50s Saturday night
behind that front.

A stronger mid level trough crossing the Northern Rockies on
Sunday will help push that front back up through Southern WI.
Light rain may accompany this warm front during the day, but
models are trending later with the storm chances. The important
feature to note this far out is that there will be a prominent
warm front with the nose of the low level jet present. This will
align with the right entrance region of an upper jet and a low-
amplitude mid level shortwave (weak intensity). The location of
this warm front/llj nose is still uncertain. A storm complex
should develop along this front Sunday evening and there should be
sufficient shear and instability for some severe storms, but we
are not sure if they will be exactly in southern WI.

The surface trough crossing WI on Monday afternoon or night could
trigger another round of showers and storms.

Cronce

&&

.AVIATION...
Issued 430 AM CDT Wed Sep 9 2026

A chance for showers and embedded weak thunderstorms to
redevelop over southern WI this morning, with some MVFR / Fuel-
Alt MVFR cloud ceilings possible with or without this activity.
Already seeing the low ceilings over the southwest corner and
central portions of the state despite the current (as of 430 AM)
lack of showers and storms.

Dry weather and decreasing cloud coverage expected from midday
onwards as a cold front advects drier air into the region. A
light southwest breeze continues ahead of the front this
morning, veering due west (and becoming breezy over central
portions of the state) behind it this afternoon. Some 15-20kt
gusts further north towards central WI. Dry weather and VFR
continue this afternoon through the rest of the TAF period.

Sheppard

&&

.MARINE...
Issued 129 AM CDT Wed Sep 9 2026

Low pressure around 29.3 inches will continue lifting northward
through the Hudson Bay today, as high pressure of 30.2 inches
builds into the central Plains. Expect southwesterly winds to
shift to northwesterly this morning into this afternoon as a
cold front moves southeastward. Thunderstorms are possible ahead
of and along this front. High pressure gradually moves eastward
into the Ohio Valley by Friday, leading to light and variable
winds across the Lake tonight through Friday morning. Winds then
become southerly and increase as low pressure deepens in the
central Plains once again. Isolated gales are possible in the
northern third Friday afternoon into Friday night. Low pressure
lifts into southern Ontario Friday night, bringing a cold front
with showers and storms and shifting winds to northwesterly
Saturday through Saturday night. Additional rain and storms are
possible Sunday into Monday as a warm front from another
developing low pressure system lifts through the region.

MH

&&

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

$$

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