NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 040946
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
446 AM CDT Fri Sep 4 2026

.KEY MESSAGES...

- Scattered showers and storms continue this morning. A few
  strong to severe storms remain possible, though we're
  transitioning to a localized heavy rainfall threat.

- Chances for scattered storm redevelopment later today into
  tonight.

- Drier weather expected for the weekend into early next week.
  Humidity persists; temperatures drop slightly but remain above
  seasonal norms.

- Shower and storm chances return midweek next week, along with
  rising temperatures.

&&

.UPDATE...
Issued 440 AM CDT Fri Sep 4 2026

The low level jet continues to feed into existing convection
over central / east-central WI early this morning, resulting in
training and back-building. 06z model guidance is split between
allowing this back-building to continue through the entire
morning (RRFS) and sweeping clean of WI and moving east over
Lake MI after daybreak (HRRR).

The way we see it, continued convection is trending more likely,
with a WAA wing already extending from La Crosse through Green
Bay likely to hold steady or slowly sag south. Primary concern
with this activity is localized heavy rainfall, particularly in
portions of east- central WI that already got plenty of rain
overnight. MUCAPE remains in the ballpark of 3000 joules, so an
additional strong or even severe storm cannot be ruled out this
morning, the only stipulation would be that all convection is
VERY elevated and freezing levels remain over 12,000 ft. The
narrow storm cores that we see on radar as I write this (at 4:30
AM CDT) are not going to get hail or wind to the ground, we
would need to see storm cores congeal and intensify before
severe wx becomes a concern again. That said, some of the 06z
guidance (RRFS) allows for this.

Area of greatest concern for locally heavy rainfall and flooding
this morning east-central WI, north of a Green Lake to Mequon
line where we observed the greatest rainfall overnight
(1-3 inches, locally higher).

Sheppard

&&

.SHORT TERM...
Issued 1104 PM CDT Thu Sep 3 2026

Current Overnight through Friday Night:

An isolated supercell thunderstorm has formed out of some
remnant convection on the eastern edge of the 850mb WAA and
capping at the 700mb level. It is generally following a MUCAPE
gradient to the SE as it tracks into east-central and southeast
WI. Given ample effective shear of 40 to 50 knots and CAPE
ahead of the storm, it is expected to maintain it's strength as
it tracks toward the MKE Metro and out over Lake Michigan into
very early Friday morning.

This evening's convection has begun to evolve more like the 00Z
Thursday run of the HRRR rather than its most recent runs this
evening, as the potential for a lead supercell was well captured
by that run. Given more details of that model run starting to
pan out for us in current radar obs, such as convection now
increasing in coverage over north central WI, the rest of the
early morning hours on Friday evolve into a training line of
convection angled from north central WI into SE WI. A heavy rain
threat may then evolve as convection moves through the area.

There's still a bit of uncertain regarding convection over
north central MN and how that will track into the area around
daybreak Friday. If it holds together and tracks along the CAPE
gradient into our area, damaging winds would certainly be a
threat. However, the current convection over north central WI
and our area may sap vital CAPE to sustain the MCS into our area
as the night goes on. For now, the assumption is that the MCS
will make it into our area, with a storms arriving in the 5am to
8am timeframe for the northeastern half of our CWA.

Following the morning storms, it does not appear that the
atmosphere will recover enough to sustain widespread storms
until Friday evening when the stationary front begins to sag
southward near the WI/IL border. Storms Friday evening should be
isolated to widely scattered.

CMiller

&&

.LONG TERM...
Issued 1221 AM CDT Thu Sep 3 2026

Saturday through Thursday:

The frontal boundary will continue southward on Saturday, moving
fairly slowly as it goes. Even though light winds will come
around to northerly Saturday, humidity will remain, and highs
will be in the low to mid 80s. Surface pressure is expected to
increase through the day, and with the front retreating south,
rain chances are not expected. High pressure will then linger
Sunday through Monday keeping us dry. Dew points will remain
somewhat elevated through the weekend as we will fail to get a
push of appreciable dry air into southern WI, though highs will
dip into upper 70s to low 80s. Warm advection then returns
Tuesday with increased chances for more thunderstorms with the
NBM painting 25 to 50% PoPs over the area. Shower and storm
chances then continue through the rest of the extended. CMiller

&&

.AVIATION...
Issued 435 AM CDT Fri Sep 4 2026

Expecting scattered shower and storm activity to remain in the
region this morning. Primary cumulonimbus cloud bases are
elevated with this activity (generally over 5,000 ft), but the
rain-cooled humid air associated with these storms has formed
some lower ceilings over portions of central and east-central
WI, anywhere from MVFR to LIFR levels.

A lull in the activity is likely at some point midday today,
followed by scattered storm redevelopment late today through
tonight. Winds will generally be light and variable through the
TAF period. Some prevailing light southwest winds midday today,
and some prevailing north to northeast winds tonight into
Saturday.

Sheppard

&&

.MARINE...
Issued 1156 PM CDT Thu Sep 3 2026

Some Marine Dense Fog may form tonight, mainly over the middle
third of the lake, close to a stalled frontal boundary.

Otherwise, the frontal boundary will remain across the Great
Lakes region through Friday. As this frontal boundary waffles
north to south across the lake from day to day, generally east to
northeast winds are expected north of the front, with east to
southeast winds south of the front. On and off thunderstorms will
be possible along and north of this frontal boundary through at
least Friday night. Then high pressure around 30.1 inches builds
over Hudson Bay on Saturday, while low pressure around 29.6 inches
moves into the northern Great Plains. Similar to earlier week
storms, widespread severe weather is not anticipated, though
isolated stronger storms with hail and gusty winds are possible.

CMiller

&&

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

$$

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