Janesville, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

624
FXUS63 KMKX 290413
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1113 PM CDT Sun Jun 28 2026

.KEY MESSAGES...

- Extreme Heat Warning in effect for all of southern WI Monday
  afternoon through Tuesday. Additional heat headlines will
  likely be needed for the middle to late portions of the week
  as this prolonged heatwave continues.

- Continued chances for showers and storms tonight especially
  for east-central WI. Then additional daily storm chances
  Tuesday night through the end of the week as the hot and humid
  pattern continues.

- High swim risk conditions for Ozaukee and Sheboygan County
  beaches on Monday, while moderate swim risk conditions for
  Milwaukee, Racine, and Kenosha Counties.


&&

.SHORT TERM...
Issued 1044 PM CDT Sun Jun 28 2026

Tonight through Tuesday:

The nose of a sly low level jet around 35-40 kt will remain over
nrn and central WI tnt. Thus new elevated showers and storms
will develop over this region due to the low to mid level warm,
moist advection and embedded frontogenesis. Believe the 12C
isotherm at 700 mb will remain a good indicator of capping to
the south, while enough lift and moisture for storms will
prevail to the north. Thus east central WI will at least be on
the srn periphery of this new area of convection. Forecasting 50
percent chances toward central WI late this evening and
overnight with only slight chances from Madison to Milwaukee.

The surface warm front will then pass nwd through srn WI from
09-15Z Mon as low pressure tracks from the central high plains
into the Dakotas. A hot, humid, and well capped airmass will
then prevail for Mon-Tue. High temps in the lower to middle 90s
with dewpoints in the middle 70s will yield heat index values of
100-110F. An Extreme Heat Warning is in effect.

Gehring

&&

.LONG TERM...
Issued 1044 PM CDT Sun Jun 28 2026

Tuesday night through Sunday:

The heatwave will continue much of the week. The strong upper
ridge axis will gradually shift to the east and south becoming a
west to east upper ridge from the ern Ohio Valley to the ern
Seaboard by Wed, and lasting through the week with only minor
weakening. Meanwhile a series of shortwave troughs will continue
to traverse from the wrn USA into the Upper MS River Valley and
nrn Great Lakes. Thus the storm track will mainly remain to the
west and north of srn WI through Thu with 500 mb heights at 588
DM or greater. This continues to place a hot and humid airmass
over srn WI through the week. Extreme Heat Warnings or Heat
Advisories will likely be needed much of the week. Only 20-40
percent chances for showers and storms toward central WI for Tue
nt-Wed nt with chances increasing a bit for late in the week
and weekend as shortwave troughs arrive in wly flow aloft.

Gehring

&&

.AVIATION...
Issued 1044 PM CDT Sun Jun 28 2026

MVFR Cigs will overspread all of srn WI late this evening into
the overnight as a warm front approaches from the southwest.
Isolated to scattered showers and thunderstorms will continue
at times tnt toward central WI but less likely from Madison to
Milwaukee and swd. The MVFR Cigs will then dissipate shortly
after sunrise but could linger longer toward east central WI.
VFR conditions will then prevail the remainder of Mon-Mon nt.

Gehring

&&

.MARINE...
Issued 1044 PM CDT Sun Jun 28 2026

Low pressure around 29.2 inches in eastern Colorado will track to
eastern North Dakota by Monday afternoon. Its warm front will
move north across Lake Michigan on Monday. Light to modest
easterly winds this evening will become breezy southeasterly
winds late tonight and Monday morning over the lake. Breezy
south winds will then prevail from Monday afternoon into the
middle of the week. Modest southerly winds will then prevail for
Thursday into Friday. Areas of dense fog may develop at times
this week due to a very humid airmass flowing over the
relatively cooler waters of the lake. Scattered thunderstorms
are forecast on most days especially over the north half.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement...WIZ052-WIZ060...4 AM Monday to 10 PM
     Monday.

LM...Small Craft Advisory...LMZ643...4 AM Monday to 10 PM Monday.

     Small Craft Advisory...LMZ644-LMZ645-LMZ646...noon Monday to
     10 PM Monday.

&&

$$

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