NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 210433
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1133 PM CDT Mon Apr 20 2026

.KEY MESSAGES...

- Temps rise well above normal Tuesday through Thursday.

- Next chances (50-80%) for showers and thunderstorms Thursday
  night.

&&

.SHORT TERM...
Issued 1130 PM CDT Mon Apr 20 2026

Today through Wednesday:

High pressure continues to trek eastward overnight with
increasing southerly flow across southern WI. Expect southerly
winds and low- level WAA to warm temps up for today with highs
climbing into the low to mid 70s. given the trend, expect some
deeper mixing to occur thus could see lower dewpoints as well.
Otherwise, looking at a mid- level ripple of vorticity to work
its way across the region during the afternoon along with a
backdoor cold front extending off of the low tracking across
Hudson Bay region. Also expecting PWATs to climb toward 0.7-1
inch and paired with cold front and a little bit of upper-level
forcing, may be enough to spur a few showers along it across
southeastern WI in the afternoon. Overall not expecting much
from this activity maybe a few sprinkles or just enough to
measure. Otherwise, the southward push off of the lake with
enhance the cooler air behind the front cooling things off
through the evening quicker than a typically diurnal pattern.

High pressure will build in behind the front overnight with
lows dipping into the upper 30s/low 40s along the lake and low
to mid 40s further inland. Wednesday is looking to another
unseasonable warm day as the upper-level ridge axis builds over
WI. expecting high temps to climb into the mid to upper 70s
inland and would not be surprised to see a few spots crack 80F.
However, temps remain cooler by the lake as the temp gradient
between land and Lake Michigan paired with the lighter winds,
will be conducive for a lake breeze to develop and push inland
into the the afternoon. Temps will remain milder overnight into
the upper 40s to upper 50s as WAA and ridge axis gradually work
its way through the area.

Wagner

&&

.LONG TERM...
Issued 1130 PM CDT Mon Apr 20 2026

Thursday through Monday:

Low pressure ejects into southern Manitoba on Thursday,
allowing for continued warm, moist advection in the form of
southerly winds gusting 20 to 30 mph throughout the day in
southern Wisconsin. High temperatures in the upper 70s are
expected away from Lake Michigan. Prefrontal/warm sector
convection will develop in the eastern Missouri River Valley
Thursday afternoon, becoming a line of storms progressing
eastward during the late overnight hours Thursday into Friday
morning. If these storms are able to tap into the available
MUCAPE (~500 J/kg) and shear (~35-40 kt), a few pockets of
damaging winds are possible along this line as it progresses
eastward through the area. With the late overnight timing and
borderline ingredients, as well as the parent low lifting into
northern Manitoba away from the Midwest, not anticipating
widespread severe convection with this activity. However, there
remains a low chance (~10-20%) for rainfall over 1 inch. This
may exacerbate any lingering river flooding. This level of
rainfall is expected to be isolated, with more widespread
accumulations around 0.5 inch.

A cold front will be progressing through the region Friday
afternoon, bringing additional chances for precipitation
(20-50%). However, amount of lift will be dependent on how much
overrunning precipitation from the previous night lingers into
Friday morning. Winds will shift to become northwesterly behind
this front, bringing in clearing conditions by Friday night.
Expect high temperatures Friday in the upper 60s to low 70s,
with overnight lows in the mid 40s.

Cooler and drier conditions are expected into the weekend under
high pressure, with highs in the low 60s and lows in the low
40s. Sunday night, low pressure ejects from the central Plains
and brings the next chances for precipitation Sunday night
through at least Monday. Model solutions diverge into Tuesday as
some (notably the GFS) models show a deepening occluding low
lingering over the Midwest through Tuesday night and other
models (ECMWF/Canadian) indicate a more progressive low with
only light showers lingering into Tuesday. Current indications
are for southern Wisconsin to remain north of the warm sector,
limiting severe potential, but flooding may become a concern.

MH

&&

.AVIATION...
Issued 1130 PM CDT Mon Apr 20 2026

VFR conditions and light winds prevail tonight into Tuesday
morning. Expect VFR conditions to persist through the day. May
see some diurnal cu develop given the milder pattern. Otherwise,
expect a backdoor cold front to work its way down Lake Michigan
through the afternoon and will see winds pick up and turn as
the front pushes through. Also may see a few sprinkles and/or
light showers develop across southeastern WI as the front slides
southward. Otherwise, light and variables winds are expected
behind the cold front for Tuesday evening into Wednesday.

Wagner

&&

.MARINE...
Issued 1130 PM CDT Mon Apr 20 2026

Lingering gusty winds and waves will keep small craft
conditions overnight into the early morning hours for nearshore
waters from Port Washington northward. Otherwise mainly
expecting a wind forecast today through midweek as southerly
winds during the day are expected to pick up before turning more
northerly with a back door cold front through the afternoon and
evening. Then light and variable winds behind the front for
tonight into Wednesday as high pressure works its way through
the region. Thursday will see southerly wind pick up as low
pressure develops across the Plains and the pressure gradient
increases. Expecting to see a cold front from this system work
its way across the lake into Friday and will also bring the next
chances for showers and thunderstorms as well.

Wagner

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643 until 7 AM Tuesday.

&&

$$

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