Janesville, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

437
FXUS63 KMKX 300306
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1006 PM CDT Sun Jun 29 2025

.KEY MESSAGES...


- Showers and storms ending late tonight. Areas of fog possible.


- Scattered thunderstorms are possible Monday primarily for
  south central and southeast WI, as the cold front moves
  through the area. Gusty winds and small hail are possible with
  the strongest storms.

- Chances for showers and thunderstorms returns later in the
  week, along with warmer and more humid conditions.



&&

.UPDATE...
Issued 908 PM CDT Sun Jun 29 2025

The initial outflow boundary has shifted south into nrn IL but
still with plenty of convection from the MKE metro area to the
IL border. Another area of showers and storms over Iowa and
Lafayette Counties will continue ewd but gradually weaken into
the early morning hours. This area of precipitation is expected
to be the last of it for the night. Areas of fog may develop
given the moist conditions and light winds. The slow moving
cold front will then pass on Monday with still a few showers
and storms possible.


Gehring

&&

.SHORT TERM...
Issued 100 PM CDT Sun Jun 29 2025

This afternoon through Monday night:

Later this afternoon the lake breeze may be enough to trigger a
few storms near the lake shore. This remains uncertain given
some capping but a few CAMs do support a few weak cells
generated off the boundary. The main thing to watch however, is
for the storm development northwest of the CWA in association
with a shortwave aloft out ahead of the surface front in
addition to a weak remnant boundary from overnight convection.
Where storms initiate will be very important this afternoon
because while instability is plentiful in the 2000-3000 J/kg
(MUCAPE) range, the shear is pretty weak overall with at most 20
kts of deep layer shear from most models. This suggests that
storms will not likely be able to maintain strength as the
outflows are likely to out run convection pretty quickly.
However, upon initiation there will be some 1000-12000 J/kg of
DCAPE in this region and thus storms could easily produce a few
severe gusts though this would likely be closer to where storms
initiate before the gust front outruns the storms. The other
thing to watch for is the potential for pop up convection
firing along outflows from the convection developing to
northwest which could become the primary risk though CAMs do not
support this type of outcome at this point. This will bring the
greatest risk for severe gusts to the northwest parts of the
CWA with lesser risk as storms expect to move southeast.

By the late evening and early overnight most of the convection
is expected to slide out with quieter conditions through the
rest of the overnight period. Most of the CAMs actually push the
front out of most of the region overnight largely bringing west
to northwest winds back to the region for Monday. Into the day
Monday another system developing across the Central Plains will
slide largely south of the region but should allow for southern
WI to get clipped which should include a period of showers and
perhaps a few storms as well with potential focus along a
lingering cold front. The broad precip shield will largely be
associated with the upper level trough pushing through bringing
PVA across most of the region with enough moisture for showers
at least. However various factors make this fairly uncertain
especially with how things develop in the lower levels and the
progression of the front and low level dry air which may
complicate how expansive rain showers could be. In addition
there is uncertainty with how northward we could see storms
Monday afternoon but right now the far southeast CWA has the
best chance for a strong to possibly even severe storm. The
better severe storm potential revolves around the deep layer
shear being in the 35-45 kt range with enough instability.

By Monday night this system will push out as high pressure fills
in behind with weak ridging gradually pushing in.

Kuroski

&&

.LONG TERM...
Issued 100 PM CDT Sun Jun 29 2025

Tuesday through Sunday:

Middle of the week we will largely be dominated by ridging to
the west and troughing to the east in a meridional flow pattern.
High pressure tracking through the Central Plains and south of
the CWA will help keep us dry Tuesday and Wednesday though
Wednesday night into Thursday a some shortwave activity swinging
off the troughing in northern Ontario. This will be something to
monitor especially as timing changes at all but there at least
appears to be a decent chance for storms Wednesday night through
at least some of Thursday. Ridging will move overhead later in
the week and likely keep the region dry with higher pressure
overhead for at least a few days (later Thursday into Saturday).
This may change however as there is fairly decent precip
chances that will ride over the ridge during this period and
minor changes in the track of the ridge could change what we
see. However for now that remains the current trend with The
ridge gradually weakening and sliding out late in the weekend
and bringing the potential for showers and storms back late
Saturday into Sunday. Uncertainty is certainly high later on as
the upper levels become fairly erratic in models.

Kuroski

&&

.AVIATION...
Issued 908 PM CDT Sun Jun 29 2025

Showers and storms ending early Mon AM with areas of fog
possible afterward. Areas of vsbys of 1-3SM BR with local 1/2SM
FG. The fog will dissipate by 13-14Z Mon. Sct-bkn030-040 for
the late morning and afternoon with showers and storms possible
due to the passage of a cold front.

Gehring

&&

.MARINE...
Issued 100 PM CDT Sun Jun 29 2025

South to southeast winds have increased today and will turn
south to southwest tonight, as weak high pressure moves east of
the region. A weak cold front will approach the region from the
Upper Mississippi River Valley later this afternoon into
tonight, moving across the region overnight into Monday.
Southwest winds will become west behind the front later Monday
into Monday night. Showers and some thunderstorms may accompany
the frontal passage. West winds should generally linger into the
middle of the week.

Kuroski

&&

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

$$

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