NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 182317
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
617 PM CDT Sat Apr 18 2026

.KEY MESSAGES...

- Overnight lows around to below freezing tonight and Sunday
  night with daytime highs only in the 40s for Sunday.

- Gradual warm up for start of the work week with above normal
  temps Tuesday through the end of the week.

&&

.UPDATE...
Issued 610 PM  CDT Sat Apr 18 2026

Ongoing forecast remains on track and no major updates.

Wagner

&&

.SHORT TERM...
Issued 140 PM CDT Sat Apr 18 2026

This Afternoon through Sunday:

Gusty west northwest winds this afternoon will continue to bring
cold air advection into the area. Clouds should generally remain
mainly broken this afternoon, before more dry air moves in the
area this evening and helps to scatter out these clouds. Winds
should weaken tonight, as a weak secondary cold front approaches
the area from the northwest. Gusty northwest winds are expected
Sunday, as high pressure moves into northern Minnesota.

Differential CVA from the passing 500 mb vorticity maximum
later tonight into Sunday may combine with low to mid-level
frontogenesis response and perhaps some column moisture to
bring mainly small chances (around 20 percent) for light rain
and snow showers Sunday morning into the afternoon. No snow
accumulations are expected. The main limiting factor for
precipitation will be some dryness in the low to mid-levels.

Otherwise, expect some clouds to move through the area later
tonight into Sunday. Ceilings should rise in the afternoon, with
higher-based diurnal stratocumulus clouds developing. Below
normal temperatures are expected into Sunday. Temperatures in
the lower to middle 40s this afternoon should drop to lows
tonight around 30 degrees, with highs Sunday in the middle to
upper 40s. It will feel like the 30s this afternoon and Sunday
afternoon with the gusty winds.

Wood

&&

.LONG TERM...
Issued 140 PM CDT Sat Apr 18 2026

Sunday night through Saturday:

Ensemble means are generally showing high pressure shifting
southeast through the region Sunday night into Monday, before
shifting to the southeast Monday night into Tuesday. This should
bring dry conditions for Sunday night into Monday night, with
temperatures slowly moderating more toward seasonal normal
values.

A cold front, perhaps more of a backdoor cold front, should
shift southward across the area Tuesday. There may be a little
instability with daytime heating from warm air advection
developing, though forecast soundings are not showing much in
the way of moisture. For now, kept Tuesday dry in the forecast.
The warm air advection Monday night into Tuesday on increasing
south winds should bring highs above normal inland, with lower
70s. Cooler values near the lake may occur with a lake breeze in
the afternoon. Despite the cold frontal passage on Tuesday,
temperatures may remain mild on Wednesday away from Lake
Michigan.

500 mb cluster analysis products are supporting an anomalous 500
mb ridge axis developing over the Great Lakes region for the
middle to later portions of next week, with an anomalous trough
to the west. This should result in southwest flow at 500 mb
over the region, with increasing south winds and warm air
advection developing again. Ensembles suggest high confidence
with a warm period to develop Thursday into Friday, with highs
possibly well into the 70s inland. There could be onshore winds
near the lake, more likely Thursday than Friday.

A strong cold front may pass east across the region later
Thursday night into Friday, bringing the next chances (40 to 70
percent) for showers and some thunderstorms.

Wood

&&

.AVIATION...
Issued 610 PM CDT Sat Apr 18 2026

Gusty westerly winds early this evening are expected to
gradually weaken as winds decouple and linger into Sunday. Then
north-northwesterly winds ramp back up fro Sunday afternoon
ahead of an incoming high pressure system building down from the
the northern Plains later in the day Sunday. With this pattern
mainly expecting VFR conditions to prevail tonight into Sunday.
There is an upper-level wave that is progged to work its way
across the Upper Midwest into Sunday and may bring a mix of
scattered rain and snow showers Sunday morning into the early
afternoon. However, any precip associated with this activity
will be battling plenty of dry air ahead of it, thus limiting
widespread impacts to southern WI terminals.



Wagner

&&

.MARINE...
Issued 140 PM CDT Sat Apr 18 2026

Breezy west northwest winds are expected today into tonight, as
strong low pressure around 29.0 inches continues to move well
to the northeast of the region, with high pressure around 30.2
inches over south central Canada.

A Small Craft Advisory remains in effect for the nearshore
waters into this evening, for the gusty west northwest winds.

The high will move southeast across the region Sunday into
Monday, with winds gradually weakening. As the high shifts east
Monday night into Tuesday, breezy southerly winds should develop
over the region.

Winds and waves may reach Small Craft Advisory levels across the
nearshore waters at times late Monday into early Tuesday, due
to the breezy south winds and building waves.

Winds and waves may reach Small Craft Advisory levels again
across the nearshore waters later in the week.

High pressure around 30.2 inches will pass by to the northeast
of the region Wednesday, with winds weakening. Winds should
become southeast to south and increase later in the week, as
strong low pressure around 29.2 inches develops in the northern
Plains.

Wood

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 10 PM
     Saturday.

&&

$$

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