Sun Prairie, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

229
FXUS63 KMKX 051046 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
546 AM CDT Sun Apr 5 2026

.KEY MESSAGES...

- Rain chances (~30-50%) return this evening evening.

- Increasing potential for pop-up snow showers Monday afternoon
  & evening, with some PM commute impacts possible.

- Active pattern continues Tuesday night into next weekend, with
  multiple additional chances for mainly rain and a few
  thunderstorms. Some wet snow is possible Tuesday night.

&&

.UPDATE...
Issued 546 AM CDT Sun Apr 5 2026

Clouds will slowly move out from west to east this morning as
drier air works into southern WI and we lose our mid level
vorticity advection and cyclonic flow. Sunshine and subtle warm
air advection will help warm temps up to around 50 for most
areas, except upper 40s toward east central WI. Winds will
continue to be gusty out of the northwest today, although
slightly lower than yesterday (less than 25 mph).

A potent mid level shortwave trough will swing through central
WI this evening and produce a period of rain showers. With temps
falling aloft, would not be surprised to see a few snowflakes
mixing in. Lows tonight will be in the lower to mid 30s, likely
just above freezing.

Cronce

&&

.SHORT TERM...
Issued 1220 AM CDT Sun Apr 5 2026

Today through Monday Night:

Synopsis/Mesoanalysis: GOES water vapor imagery depicts several
prominent features influencing both ongoing and short term weather
conditions late this evening. An upper low continues to progress
east toward Ontario, with residual lift on the back side of the low
supporting isolated sprinkle or flurry potential moving into the
predawn hours. Further upstream, a pair of shortwaves are apparent
over Lake Winnipeg & the Northwest Territories. The two shortwaves
will progress southeast during the period, with the leading
perturbation moving across Wisconsin from late Sunday afternoon into
early Monday morning. Lift from the wave, in addition to forcing
from a surface cold front moving across southern Wisconsin, will
support returning rain chances Sunday evening through the predawn
hours Monday. Conditions will dry out after sunrise Monday, with
precip-free weather lasting into the first part of the afternoon
hours. Precip chances return late Monday afternoon into Monday
evening as the wave currently over the Northwest Territories settles
over Lake Huron. Late afternoon/early evening timing, along with
very cold temperatures aloft, will support greater snow potential in
the Monday afternoon/evening round of precipitation. If wintry
precipitation does materialize, Monday evening commute impacts will
be possible.

Rest of Tonight: Widespread precipitation potential has ended,
though a few light sprinkles or flurries remain possible through the
predawn hours as an upper low departs the region. Best potential
will be along & north of I-94, where proximity to the vacating low &
its residual forcing will be greatest. Whether any drops or flakes
reach the surface remains uncertain, as steady drying will be
ongoing in the lower portions of the column. Have accounted for the
isolated potential with 10-15% precip probabilities through 5 AM,
and will make adjustments as radar/obs trends call for through the
overnight. Not expecting any measurable accumulation or impacts in
any flurries/sprinkles that occur late tonight.

Sunday Night: Rain chances return ahead of an encroaching shortwave
and surface front. Projected surface temperatures and forecast
soundings suggest that thermal profiles will be mild enough for all
rain, so have continued an all rain forecast in the evening update.
Will nevertheless need to monitor trends in east-central Wisconsin,
where some wet snowflakes could mix in if conditions trend cooler
than current guidance suggests. Not expecting meaningful
accumulations or impacts in the event that some wet snowflakes mix
in with rain over east-central Wisconsin.

Monday Afternoon/Evening: Potential is increasing for pop-up snow
showers as a second upper wave moves over the Lake Huron vicinity.
Current expect the best snow shower potential to reside over east-
central Wisconsin, where proximity to the encroaching wave will be
greatest. Anticipate a strong diurnal contribution to activity given
very cold temperatures aloft & breaks in the cloud cover through the
early afternoon time frame. Forecast soundings depict deep mixing
from the surface to/through the 700 mb level, with some modeled
profiles hinting at some small CAPE in the event that sufficient
surface heating is realized. Will thus need to watch for a more
convective character in snow showers, which would act to boost
snowfall rates. Hit & miss nature of the snow showers, in
addition to potentially enhanced rates within them, could thus
lead to rapid changes in visibility over short distances Monday
afternoon & evening. Will thus be watching closely for possible
commute impacts over coming updates.

Quigley

&&

.LONG TERM...
Issued 1220 AM CDT Sun Apr 5 2026

Tuesday through Sunday:

Tuesday night through Wednesday: The next disturbance arrives over
the western Great Lakes, bringing the next chances for precipitation
to southern Wisconsin. Precip will begin Tuesday night as a wing of
broad warm advection & affiliated frontogenesis spreads north across
the region, with precipitation chances continuing into the day
Wednesday as a surface cold front approaches & crosses southern
Wisconsin. Overnight timing of the initial WAA/FGEN precipitation,
in addition to cold antecedent temperatures, may support snow or
rain/snow mix through Tuesday night, with the column becoming mild
enough for all rain by Wednesday morning. Will thus need to monitor
trends for some potential snow accumulation Tuesday night into early
Wednesday morning. While most appreciable probabilities for 1"+ of
accumulation remain over north-central and northeast Wisconsin, 40%+
probabilities of at least trace accumulations sag into our northern
two tiers of counties. Will continue to monitor trends. LREF
guidance hints at some weak (< 100 J/kg) MUCAPE building into the
area ahead of the Wednesday PM cold front, so a few rumbles of
thunder could mix in with rain on Wednesday. Currently expecting
severe weather potential to remain over the central Great Plains,
where instability is progged to be much higher.

Thursday through Sunday: Broadly divergent upper level winds &
embedded mid-level waves will support continued periods of on again
off again precipitation. Initial temperature forecasts appear mild
enough for all rain. Could see a few thunderstorms mixing in with
rain if sufficient CAPE can build into the western Great Lakes,
though far greater storm potential will remain concentrated in the
Great Plains where instability will be maximized.

Quigley

&&

.AVIATION...
Issued 546 AM CDT Sun Apr 5 2026

There were a few pockets of snow showers early this morning,
along with gusty WNW winds, but they are moving out and clouds
will gradually clear from west to east through late morning. By
clearing, I mean there should be a brief period of full sun west
of Madison this morning, but then I expect few to scattered
diurnal cumulus clouds the rest of the day. Gusty NW winds will
continue through the afternoon.

Expect a period of rain showers to quickly move across central
and southern WI this evening. With temps falling aloft, would
not be surprised to see a few snowflakes mixing in.

Cronce

&&

.MARINE...
Issued 1220 AM CDT Sun Apr 5 2026

1002 mb low pressure is moving toward the Ontario-Quebec border this
evening, resulting in continued gusty northwest winds across the
open waters of Lake Michigan. Said gusty winds will continue into
Sunday morning as the low deepens to near 988 mb over Quebec. The
potential for a few gale force gusts will continue through Sunday
morning across the northern third of Lake Michigan. Continue to
anticipate that that headlines won`t be necessary given the isolated
nature of any such higher gusts. Winds will taper Sunday afternoon &
night as 1030 mb high pressure builds into the Great Plains.
Scattered rain and snow showers ongoing through this evening will
taper through the second half of the overnight hours tonight.
Additional rain and snow showers are forecast Sunday night into
Monday.

Northwest winds will increase once more during the day Monday as a
small area of 1016 mb low pressure develops over Lake Huron. Similar
to ongoing conditions, a few gale force gusts are possible over the
northern half of the open waters during the afternoon hours, but are
expected to be isolated and brief enough to preclude the need for
any headlines. Trends will continue to be monitored. Winds will
decrease Monday night into Tuesday as 1032 mb high pressure moves
over and east of the open waters. Areas of moderate freezing spray
are possible over the northern half of the lake Monday afternoon and
evening.

1002 mb low pressure will form over the northern Great Plains &
approach Lake Michigan Tuesday night into Wednesday, resulting in
increasing southerly winds across the waters. Winds will remain
gusty into Wednesday night as the low passes near or just north of
northern Lake Michigan. Will be monitoring for more widespread gale
potential during this time frame, with the need for headlines being
evaluated as this portion of the period draws closer. Winds will
taper during the day Thursday, when 1030 mb high pressure is
forecast to move from the northern Great Plains toward Lake
Superior. Showers and a few thunderstorms are expected Wednesday
into Thursday, with severe weather potential appearing low at this
time.

Small Craft Advisory conditions continue in nearshore zones through
Sunday afternoon, with additional advisory conditions anticipated
during the day on Monday. Will handle Monday`s conditions with a new
headline once the ongoing Small Craft Advisory expires. Winds and
waves will taper Monday night into Tuesday. Wind gusts will increase
once more Tuesday night through Thursday as low pressure approaches
from the northern Great Plains. Expect that at least Small Craft
Advisories will be necessary during this time frame, with gale
potential being monitored over coming forecasts.

Quigley

&&

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

&&

$$

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