NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 040529
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1229 AM CDT Sat Apr 4 2026

.KEY MESSAGES...

- Additional rainfall moving west to east will bring up to an
  additional inch of rainfall, leading to local ponding of water
  and potential for river flooding.

- Seasonal temps and dry weather Sunday into early next week.

- Return to an active pattern Tuesday night through the weekend,
  with chances for rain and storms developing on and off through
  the week.

&&

.SHORT TERM...
Issued 1230 AM CDT Sat Apr 4 2026

Today through Sunday night:

Severe thunderstorm threat has diminished greatly over the last
few hours, with mid-level instability too strongly undercut by the
cold airmass at the surfaces. MUCAPE gradient is leaning into Lake
Michigan as the parent low propagates into southern Wisconsin
this morning, so any lingering threat remains tied to long-
duration rain and storms. Expecting up to an additional inch of
rain in many areas, which is expected to lead to local ponding of
water and rising rivers.

Temperatures in the mid-30s have been observed across all of
southern Wisconsin for the last several hours, and although
expectations remain for temperatures to remain above freezing,
cannot rule out a localized lower elevation area seeing
temperatures fall to freezing for a few hours early this morning
and allowing for patchy freezing rain. This is especially true for
Marquette, Green Lake, Fond du Lac, and Sheboygan Counties, but
could dip down into the Dodge/Washington County areas as well. Not
anticipating widespread impacts. Temperatures will rise into the
upper 30s and low 40s just before sunrise as low pressure
propagates through the region, bringing a wave of warmer surface
air with it. This will bring an end to any freezing rain concerns.

Overcast skies continue throughout the day, with high temperatures
in the upper 40s to low 50s and breezy westerly winds around 25
mph. During the afternoon hours, wrap-around showers and sprinkles
may develop across southern Wisconsin (~15% chance, isolated to
scattered coverage). A few flurries may develop overnight as
temperatures fall to just below freezing. All precipitation ends
by Sunday morning.

Highs around 50 degrees expected Sunday, before 500 mb shortwave
works its way southeastward through Wisconsin Sunday evening
through Sunday night, bringing isolated to scattered rain showers
to the region (15-30% chances). A few snowflakes could mix in at
times, with temperatures in the low to mid-30s Sunday night as
Canadian high pressure builds into the region.

MH

&&

.LONG TERM...
Issued 1230 AM CDT Sat Apr 4 2026

Monday through Saturday:

The aforementioned 500 mb shortwave looks to phase with the
lingering remnants of a cold front draped across the Ohio Valley,
allowing the shortwave to deepen a surface through and bring in
additional precipitation on Monday. Current expectation is that
the majority of this precipitation will be confined to northern
and central Wisconsin as high pressure builds into the Upper
Mississippi Valley and presses moisture northward, but cannot
rule out a few showers (~15% chances) in southern Wisconsin on
Monday.

High pressure then dominates Monday night through Tuesday, before
quickly moving eastward in advance of a low pressure system
propagating through southern Canada Tuesday night through
Wednesday. Chances for precipitation return with this system as
warm frontogenesis develops over Wisconsin Tuesday night, although
confidence in coverage is not high at this time (keeping NBM PoPs
around 20-40%). Temperatures in the warm sector on Wednesday will
rise into the mid 60s away from Lake Michigan. Overnight
Wednesday, a weakened cold front from this system looks to push
southeastward through the Upper Midwest, but looks to stall as the
low continues its eastward progression and weakens while low
pressure develops in the Colorado Rockies on Thursday. Models
diverge with solutions for this low, some tracking it rapidly
through the Upper Midwest, while others have it deepening and
tracking southward. An active pattern remains in play through
Saturday.

MH

&&

.AVIATION...
Issued 1230 AM CDT Sat Apr 4 2026

Isolated thunderstorms continue across southeastern Wisconsin,
while a line of thunderstorms with trailing rain showers moves
eastward through southwestern Wisconsin. Expect this line of
storms to continue eastward, exiting into Lake Michigan by
daybreak. Temperatures hover near 33 degrees F at SBM, but still
expecting little to no freezing rain concerns. Temperatures will
begin to rise before sunrise as low pressure moves overhead. Low
pressure overhead will bring IFR ceilings and briefly lower winds,
turning to become westerly and gusting at 20-25 kt after sunrise
as low pressure exits to the east. Expect ceilings to recover into
MVFR into midday/afternoon, but isolated to scattered rain
showers with snowflakes mixing in at times (15-30% coverage)
develop during the evening to overnight hours and may briefly
reduce ceilings as they move overhead.

MH

&&

.MARINE...
Issued 1230 AM CDT Sat Apr 4 2026

Northeasterly winds will continue to gust near 30 kt into the
early morning hours, with a few gales expected in the far
northern portions of the lake. Winds will gradually veer through
the day Saturday as low pressure around 29.6 inches crosses the
northern portions of the lake. Thunderstorms will continue across
the southern half of the lake through the early morning hours,
with lightning as the main threat. Thunderstorms will end into the
mid-morning hours as low pressure exits into Ontario and deepens
to 29.3 inches. Expect winds to become westerly and gust again
around 30 kt through tonight as this low deepens.

Winds veer northwesterly and gradually diminish Sunday as low
pressure exits into northern Quebec. A weak low around 30.0 inches
in southern Quebec will bring gusty conditions again Sunday night
into Monday morning, with winds remaining northwesterly. As low
pressure exits into Monday night, expect a few gales to develop
and winds to shift northerly. High pressure builds into the Upper
Midwest into Tuesday, with winds becoming light and variable.
Winds shift back to southerly as low pressure develops in the
northern Plains into Wednesday.

MH

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 1 PM
     Sunday.

&&

$$

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