Sun Prairie, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

936
FXUS63 KMKX 261943
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
243 PM CDT Thu Jun 26 2025

.KEY MESSAGES...

- Strong to severe thunderstorms are expected this afternoon and
  evening. Initial storms this afternoon will include a tornado
  threat, with strong winds becoming more likely with storms
  during the evening.

- Somewhat cooler and relatively quiet weather expected Friday
  and Saturday, before temperatures turn much warmer/more humid
  on Sunday.

- A cold front will bring temperatures back to around average
  for much of next week.

&&

.SHORT TERM...
Issued 243 PM CDT Thu Jun 26 2025

Rest of this Afternoon through Tomorrow:

Main focus for this afternoon and evening will be severe weather
potential. As of 2 PM, a warm front stretched across south
central Wisconsin, generally just north of the I-94/US 18
corridor, curving back southeastward near Lake Michigan. As low
pressure along the Iowa/Minnesota state line moves east-
northeastward, this warm front will continue to slowly move
northward. Convection should expand along the warm front this
afternoon, though the spatial extent is still in question given
the relatively weak lift. That said, anything that becomes
rooted in the boundary layer will have a very unstable airmass
to work with, with MLCAPE in excess of 2000 J/KG. There is also
a substantial amount of low level CAPE, with 0-3 KM values
between 100 and 200 J/KG.

While Low level shear isn`t terribly impressive, the strong low
level instability and localized increase in helicity associated
with the warm front may be sufficient for a tornado threat with
this afternoon`s convection, along with a few strong wind
gusts. Weak mid level lapse rates and high freezing levels
suggest that while a few instances of severe hail are possible,
it should not be widespread.

Later this evening focus will then shift to a line of storms
moving in from the west. These will be more likely to contain
damaging wind gusts compared to the afternoon convection, along
with a somewhat lower tornado threat. Any eastward surges in the
line, especially if collocated with the warm front or an
outflow boundary, will still pose a risk for QLCS circulations,
however.

Storms will gradually weaken with eastward extent this evening, with
the severe weather risk expected to largely dissipate by
midnight. A few showers may linger into Friday morning, but
otherwise most of the day on Friday should be dry. Highs
tomorrow will be cooler, with upper 70s to around 80 expected.
Winds will turn more northwesterly by afternoon helping to usher
some lower dewpoints into the region as well.

Boxell

&&

.LONG TERM...
Issued 243 PM CDT Thu Jun 26 2025

Tomorrow Night through Thursday:

High pressure will sink south into the region late tomorrow
night, setting the stage for what should be a fairly pleasant
Saturday. Highs Saturday will range from the low to mid 80s,
warmest southwest of Madison, with dewpoints in the low to mid
60s. A few showers or thunderstorms will be possible on Saturday
near the state line, as a shortwave ripples through.
Thunderstorm chances then increase area-wide late Saturday night
and especially Sunday as a cold front sharpens to the northwest.
This looks to pass through the area Sunday night, with an
associated increase in PoPs through the afternoon and evening
hours Sunday. Ahead of the front, a very warm and humid day is
expected, with highs Sunday around 90. A Heat Advisory may
eventually be needed for parts of the area, as heat indices will
top out around 100.

A few days of northwest flow will bring highs back to more
average values, with highs in the low to mid 80s, and overnight
lows in the low 60s. Dewpoints are also looking more tolerable,
with values in the low to mid 60s most days.

Boxell

&&

.AVIATION...
Issued 243 PM CDT Thu Jun 26 2025

Convection is starting to develop across the area this
afternoon, with scattered thunderstorms expected through the
afternoon hours. Later this evening, additional storms will
arrive from the west, likely in the form of a line or broken
line. Strong winds will be possible with both this afternoon and
evening`s storms, along with reduced visibility and ceilings.

Convection will persist into this evening, but will gradually
weaken over time. Showers and low ceilings may persist into
early Friday morning, before more quiet weather arrives for the
day Friday.

Boxell

&&

.MARINE...
Issued 243 PM CDT Thu Jun 26 2025

Low pressure of 29.8 inches will move across the Iowa and
Minnesota border today, reaching Wisconsin tonight. A stationary
front will stay parked over the southern end of the lake into this
evening with southerly winds south of the boundary and north to
northeast winds north of the boundary. As the surface low
approaches tonight, winds will come around to southwesterly over
the whole lake and thunderstorms are expected over much of the
open waters. The low is then expected to pass early Friday
morning, dragging a cold front over the lake. Winds will become
westerly and northwesterly early Friday, becoming northerly
Friday night as high pressure of 30.0 inches moves through the
area.

Winds return to a southeasterly to southerly direction Sunday as
the high moves east of the region.

Boxell

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

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