Sun Prairie, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

222
FXUS63 KMKX 030335
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1035 PM CDT Wed Apr 2 2025

.KEY MESSAGES...

- Areas of fog will linger until around midnight, when
  southwesterly winds are anticipated to mix the fog and raise
  visibility.

- The next disturbance approaches Friday night through Sunday,
  bringing additional precipitation to southern Wisconsin.
  Mostly rain appears favored at this time.

&&

.UPDATE...
Issued 1026 PM CDT Wed Apr 2 2025

Areas of fog will persist over east central Wisconsin for the
next hour or two before southwest winds and the passage of a
cold front increase mixing and cause fog to dissipate.
Otherwise, gusty winds will persist overnight as modest CAA
brings steeper low to mid level lapse rates into the region
overnight and cooler surface temperatures.

CMiller

&&

.SHORT TERM...
Issued 130 PM CDT Wed Apr 2 2025

This Afternoon/Early Evening:

An afternoon of rapid changes is upon us as a strengthening
surface low over north central IA moves to the north northeast.

An astoundingly strong mid level jet will spread over the area
over the next few hours. The core of this jet is 120kt, with a
broader area of 90-100 knots expanding well to the southeast.
The surface low passage and mid level jet have carved an area of
clearing that has spread into much of central/eastern IA.

In southern WI, we are still socked in with clouds and a surface
warm front remains to our south. This warm front has been
gaining some speed to the northeast with the surface low on the
move into south central MN. Initially, this will bring and
increase in dewpoints (low/mid 50s) with a wind shift to the
southeast. Temperatures will continue to hold near dewpoints
given extensive stratus and lingering showers.

Heading into the mid afternoon hours, expectations are for
stratus to scatter out a bit from southwest to northeast,
allowing for temperatures to rise through the 50s and into the
60s (where sunshine is observed the longest). This will aid in
increasing CAPE, particularly in the low levels (0-3km). Recent
CAM runs produce around 500 J/kg (give or take) for areas mainly
along and south of the I-94 corridor.

As of this hour, we are seeing cumulus development over central
Iowa near a pre frontal trough. This will be an area we watch
very closely as the afternoon progresses as temperatures have
surged into the 60s with dewpoints in the 50s. Recent HRRR runs
do suggest convective initiation over the next couple of hours,
moving across southern WI during the mid afternoon to early
evening hours. Inheriting this activity will be our best bet
for storms as initiation overhead this afternoon looks very
difficult. The aforementioned mid level jet and the associated
warm advection limits our mid level lapse rates considerably
(closer to 5 C/km).

Storms that do enter from the west should be scattered in nature
and relatively low topped. With the increasing low level lapse
rates and CAPE, tapping into strong winds just above the surface
is the main concern. It would not be hard to support 60mph gusts
with 50kt of wind at 850mb. If supercellular characteristics
can be sustained, there will be a hail and low end tornado
threat. A failure point for convection that needs to be
mentioned is our extreme effective shear (90+ kt). While forcing
will help, CAPE looks to be meager overall and the amount of
shear may be too much and storms end up being ripped apart.

Gagan

Tonight through Thursday night:

High pressure will develop directly behind the departing low
moving through upper Great Lakes and into Ontario tonight into
Thursday morning. While winds may initially remain breezy with
the high impinging on the low the high will eventually move
overhead and bring lighter west to northwest winds back to the
region by Thursday afternoon. While the upper levels remain
active a lack of moisture in the upper levels will keep us dry
at the surface though skies may not clear out fully.

Thursday night expect quiet conditions to continue as moisture
gradually slides north through the night with activity in the
upper levels not expected to bring us precip until at least
Friday afternoon.

Kuroski

&&

.LONG TERM...
Issued 200 PM CDT Wed Apr 2 2025

Friday through Wednesday:

Another period of rain should move into at least the southeast
portions of the area for Friday night, as low pressure moves
northeast along a stationary frontal boundary to the southeast of
the area. Leaned towards the GFS/ECMWF and EPS/GEFS track, which
is mainly over northeast Illinois. The NAM is further northwest of
the forecast area and appears too far to the northwest.

The best upward vertical motion may stay to the southeast of the
area during this period per the EPS/GEFS, but should remain close
enough to warrant leaving likely (55 to 70 percent) PoPs in the
forecast for the southeast parts of the area Friday night.
EPS/GEFS also show 30 to 60 percent chances for 0.10 inches of
liquid precipitation or greater Friday night in southeastern parts
of the area, with all ensemble members in this area showing
measurable precipitation. This gives confidence in the southeast
for the highest PoPs Friday night.

Cold air advection on northwest winds then occurs Saturday into
Saturday night, bringing somewhat cooler temperatures into the
area by Sunday.

500 mb Cluster Analysis forecasts for Sunday into Monday are
mostly favoring a deep trough to develop across Ontario and
Quebec, extending southwestward into the Great Lakes region. This
trend should favor cold front shifting south through the area
Sunday night or Monday morning. Below normal temperatures should
occur during this time as well, coldest on Monday per EPS/GEFS
ensemble members. The chilly temperatures should linger into
Tuesday.

There is some light snow potential as well with and behind the
front later Sunday night into Monday night, as differential CVA
from passing vorticity maxima shift through with some low level
moisture and steep low level lapse rates. Things look to dry out
for Wednesday, with temperatures slowly rebounding away from Lake
Michigan.

Wood

&&

.AVIATION...
Issued 1031 PM CDT Wed Apr 2 2025

Expecting fog near KSBM and the immediate lakeshore to dissipate
around and after 06Z as a cold front passes and drier air gest
ushered into the region on southwest winds. While VFR exists
easts of Madison, MVFR clouds are expected to move in overnight
with the cold advection regime and linger into the first half of
tomorrow. Clouds may linger through the day but raise to VFR
tomorrow afternoon.

Southwest winds will persist overnight with southwest wind
shear from 45 to 50 knots into the early morning hours. Wind
shear should subside before dawn and gusty winds will persist
into tomorrow afternoon before easing, with winds becoming WNW-
erly tomorrow afternoon.

CMiller

&&

.MARINE...
Issued 200 PM CDT Wed Apr 2 2025

A Gale Warning remains in effect for the entire open waters
until 0z lingering longer in the far north. The surface low of
29.2 inches will progress toward Lake Superior this evening,
moving into Ontario by early Thursday morning. We cannot rule
out a few stronger storms across the far southern portions of
the lake late this afternoon into the evening. Winds will turn
southwesterly & gradually decrease in the wake of the departing
surface low tonight. Gale Warning in the nearshore ends 4z with
a prolonged Small Craft following it into Thursday afternoon

30.1 inch high pressure will build into the northern Great Plains
Thursday afternoon, allowing winds to turn more westerly across
the open waters. There is increasing potential for a period of
Gales in the far north early Thursday lasting into the
afternoon. Thus we have issued another Gale Warning for the
northern parts of the lake from 9-19z. Winds will become light
& variable Thursday night as the high crosses Lake Michigan.
Winds will shift out of the northeast on Friday as low pressure
forms in the southern Great Plains. Winds will increase during
the day on Saturday as the low moves into the Ohio River Valley.
Gales aren`t forecast at this time, though trends will be
monitored. Periods of rain will accompany the approaching low
Friday afternoon through Saturday, with a few thunderstorms
possible over far southern Lake Michigan.

Kuroski

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ563...4 AM Thursday to
     2 PM Thursday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 PM
     Thursday.

&&

$$

Visit us at weather.gov/milwaukee

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/NWSMilwaukee
www.twitter.com/NWSMilwaukee
www.youtube.com/NWSMilwaukee