NWS-Milwaukee/Sullivan Forecast Discussion

						FXUS63 KMKX 300449
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1149 PM CDT Wed Apr 29 2026

.KEY MESSAGES...

- Areas of frost expected tonight. Frost will be most widespread north
  of I-94 and west of I-41.

- Patchy fog possible in low-lying spots tonight.

- Additional frost expected Thursday night and Friday night,
  with freezing temperatures possible away from Lake Michigan.

- Pop-up showers continue during the afternoon hours Thursday
  and Friday. Some graupel could mix in with the rain.

- Additional shower & thunderstorm chances Sunday night through
  the middle of next week.

&&

.SHORT TERM...
Issued 1145 PM CDT Wed Apr 29 2026

Rest of Tonight through Saturday Night:

Synopsis/Mesoanalysis: A broad upper trough will remain entrenched
across the western Great Lakes through the first half of this
weekend. Embedded small-scale perturbations will progress through
the broad area of troughing, combining with daytime heating to
support additional periods of pop-up rain showers across southern
Wisconsin both Thursday and Friday afternoon. Hazards aren't
expected in any additional shower development, though a few graupel
pellets could mix in with the rain drops. Conditions will dry out on
Saturday as shortwave ridging moves in from the Northern Plains.
Broad high pressure over the Canadian Great Plains will maintain
north-northwest breezes across the region through Friday night,
resulting in continued below normal temperatures. Anticipate areas
of frost development during the overnight periods tonight, and once
again on Thursday night and Friday night. Frost Advisories remain in
effect for parts of southern Wisconsin tonight, with additional
headlines anticipated through the end of the week. Be sure to bring
any cold-sensitive plants indoors during overnight periods.

Rest of Tonight: Any last showers will push out of east-central
Wisconsin after midnight, giving way to at least partly clear skies
across southern Wisconsin. Clearing skies will combine with light
surface winds to cool overnight lows. Temperatures in the low-mid
30s will combine with the aforementioned light surface winds to
support areas of frost, with the most widespread potential generally
expected to the north of I-94 and west of I-41. Expected coverage of
more widespread frost potential has increased in the evening
forecast update, with Fond du Lac, Dodge, Washington, Jefferson,
Dane and Waukesha Counties being added to the pre-existing Frost
Advisory between 12 AM and 8 AM. Be sure to move any cold-sensitive
plants inside in any of these locations. Ongoing in current obs,
brief pockets of shallow fog could precede frost development,
with the expectation for a relatively quick transition to frost
as a very shallow near-surface moist layer deposits out.

Thursday: Fair-weather cumulus clouds will quickly blossom from late
morning into the afternoon as the surface heats beneath an overall
cold column overhead. With time, expect that said cumulus will grow
deep enough to support hit & miss shower development across the
area. Not anticipating any hazards in this activity, though an
overlap of very weak MUCAPE & very cold temperatures aloft could
support some graupel pellets in any deeper updrafts. No impacts are
anticipated.

Thursday night: Expecting colder overnight lows relative to tonight,
with another round of frost development forecast over southern
Wisconsin. Anticipating that widespread frost coverage will be
higher compared to tonight, with a larger part of the area likely
needing a Frost Advisory. Will be addressing the need for Thursday
night frost/freeze headlines in the Thursday afternoon forecast
update.

Friday: Another round of diurnal rain showers is forecast, though
coverage might be a touch lower compared to Thursday. Some graupel
pellets could mix in with rain once more given still very cold
temperatures overhead.

Friday night: Anticipating another round of widespread frost
development, with additional frost headlines likely. Details
regarding the precise timing & placement of headlines will be
refined in coming forecasts.

Quigley

&&

.LONG TERM...
Issued 1145 PM CDT Wed Apr 29 2026

Sunday through Wednesday:

Synopsis: Shortwave ridging will be short-lived/confined to the day
on Sunday, with a renewed area of mean troughing becoming
established from the Hudson Bay to the western Great Lakes through
most of the long term period. Positioning of the trough will place
southern Wisconsin in line for additional shortwave & surface
frontal passages Sunday night through the middle of next week, with
each shortwave/surface front passage bringing chances for additional
showers and thunderstorms. Near or slightly below normal
temperatures & only modest moisture returns are expected to keep
thunderstorms below severe levels, though trends will continue to be
monitored over coming forecasts.

Sunday through Monday: Currently anticipating a pair of shower &
thunderstorm chances across southern Wisconsin as two shortwaves &
surface fronts move through the western Great Lakes. Currently
favored periods are Sunday afternoon/evening and Monday
evening/night, with precise trends being refined in coming
forecasts. MUCAPE will be sufficient for a few thunderstorms in each
batch of activity, with current progs from the LREF implying low
enough values to keep activity sub-severe. Will nevertheless be
monitoring trends over coming updates.

Tuesday into Wednesday: Additional showers & storms are forecast as
another upper wave and surface front move through the region. Have
largely maintained precip forecasts from that of the NBM, which
depicts broad 20-40% probabilities over most of this time frame.
Maintained these probabilities not because it will be raining for
the entirety of the Tuesday-Wednesday time frame, but rather that
high spread remains amongst global guidance regarding the precise
timing of the upper wave and frontal passage. Anticipate that the
range of mentionable precip probs will decrease as timing/placement
trends clarify through this weekend.

Quigley

&&

.AVIATION...
Issued 1145 PM CDT Wed Apr 29 2026

SHRA/DZ are ending this evening, with activity persisting for
another hour or two at SBM. Some shallow FG/BR has developed in
low-lying spots, with the expectation for activity to deposit
out as frost through the second half of the overnight. Will be
accounting for ongoing trends through the near-term in the 06Z
update. Clouds will thicken during the mid-late morning hours
Thursday. Additional RA or SHRA is anticipated Thursday
afternoon and evening. Similar to this afternoon, precipitation
will be hit and miss in nature, with the need for prevailing
SHRA/RA groups remaining uncertain at this time. Have thus
maintained PROB30 SHRA/RA groups at southern Wisconsin terminals
Thursday afternoon & evening, with TEMPO and/or prevailing
groups being inserted as timing & location trends become clearer
in coming forecasts.

Quigley

&&

.MARINE...
Issued 1145 PM CDT Wed Apr 29 2026

Widespread gales are not expected through the duration of the period
across the open waters of Lake Michigan. Currently north-northwest
winds will continue through the end of the week as 1002 mb low
pressure shifts into the Canadian Maritime Provinces & 1022 mb high
pressure builds into the northern Great Plains. Winds will trend
south-southwesterly Saturday into Sunday as the aforementioned area
of high pressure moves into the Ohio River Valley and 1000 mb low
pressure forms over the Hudson Bay. Winds will briefly veer westerly
Sunday night into Monday as a weak cold front crosses Lake Michigan.
Showers and a few thunderstorms will accompany the front, with
severe weather not anticipated at this time.

A second area of stronger low pressure near 992 mb will develop over
the Lake Superior vicinity during the day Monday, ultimately
shifting toward the southern Hudson Bay and Quebec on Tuesday.
Progression of the low will allow winds to trend west-southwesterly
Monday night through Wednesday. A cold front is forecast to cross
the open waters Wednesday afternoon, bringing a northwest wind
shift. Additional periods of showers and embedded storms are
forecast Sunday night into the middle of next week, with widespread
severe thunderstorms not expected at this time.

Widespread Small Craft Advisory conditions are not expected through
the duration of the period in nearshore zones. West-northwest winds
will continue tonight through the end of the week as high pressure
builds in from the northern Great Plains. Winds will trend west-
southwesterly this weekend as low pressure develops near the Hudson
Bay. Winds will trend westerly Sunday night into Monday morning as a
weak surface front crosses Lake Michigan. West-southwest winds
return Monday afternoon into Wednesday as a second surface front
approaches Lake Michigan from the west. Periods of showers &
embedded thunderstorms are forecast Sunday night into Monday, Monday
evening, as well as Tuesday into Wednesday. Severe weather is not
anticipated at this time, though trends will continue to be
monitored.

Quigley

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory...WIZ046-WIZ047-WIZ051-WIZ056-WIZ057-WIZ058-
     WIZ059-WIZ063-WIZ064-WIZ065 until 8 AM Thursday.

LM...None.
&&

$$

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