Janesville, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

849
FXUS63 KMKX 041933
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
233 PM CDT Mon May 4 2026

.KEY MESSAGES...

- Special Weather Statement remains in effect for elevated fire
  weather concerns today given warm and dry conditions with
  breezy winds.

- Chances for showers and thunderstorms (30 to 50 percent
  chances) remain for Monday afternoon and evening, as a cold
  front moves through the area. Gusty winds could occur with
  stronger storms.

- Warmer and breezy through this evening, then cooler the rest
  of the week.

- Frost may occur toward the middle to later portions of the
  week.

&&

.SHORT TERM...
Issued 155 PM CDT Mon May 4 2026

Tonight through Tuesday night:

Gusty southwest winds up to 40 mph, large dew point depressions
around 30 degrees, and high temperatures in the mid to upper
70s will support elevated fire weather conditions. See the fire
weather section for more details.

A cold front is expected to move over the area between 3pm and
10pm this afternoon and evening. The boundary layer remains well
mixed this afternoon, with large dewpoint depressions near 35
degrees in the low levels. Some moisture advection may occur
over south central and southeast WI ahead of the front late
this afternoon, but the Tdds will still be around 25, and storms
will remain high based.

CAMs have suggested that widely scattered storms will form
along the front over south central WI between 5pm and 7pm this
evening and then track southeast with time, generally losing
strength as skinny CAPE profiles supporting ~500 J/kg SBCAPE
likely get utilized/entrained fairly quickly. Given the dry low
levels, a high plains-like environment is present, which may
support gusty winds with any storms that develop as rain
evaporates into the dry low-level environment. Small hail can`t
be ruled out as well, as mid level lapse rates are steep at
around 7 C/km. The skinny CAPE will limit hail size however.

The front is expected to clear tonight, with some low end
potential (15 to 20% PoPs) for light, post-frontal showers and
sprinkles through dawn on Tuesday.

Otherwise quiet, cooler, and dry on Wednesday with highs in mid
to upper 50s. High cloud cover will linger through the day due
to the lingering effects of the front to our south over
Illinois. Areas of frost are then possible Tuesday night into
Wednesday along the Kettle Moraine.

CMiller

&&

.LONG TERM...
Issued 215 PM CDT Mon May 4 2026

Wednesday through Monday:

Cool conditions persist Wednesday and Thursday as troughing
remains over the region aloft. More widespread frost is possible
area-wide Wednesday night into Thursday. Shower activity is then
expected Thursday as the base of the trough pivots through the
area. The combination of PVA and steep lapse rates may support
shallow convection capable of pea-sized hail.

Warming is then anticipated Friday through Sunday as warm
advection occurs over the region. Some WAA driven showers may
occur during the afternoon, with then relatively quiet
conditions Saturday. Saturday night into Sunday, another wave of
mid level warm advection and a sfc trough will support more
showers, with things then largely drying out late Sunday into
Monday.

CMiller

&&

.AVIATION...
Issued 154 PM CDT Mon May 4 2026

Gusty southwest winds with occasional gusts between 35 and 40
knots will continue through the next few hours. Winds will
remain elevated early this evening, but will generally ease to
gusts around 25 knots as a cold front works into the area.
Thunderstorm activity along the front is expected to be widely
scattered, but given the dry low levels, gusty winds can`t be
ruled out with any storms that occur. The front is expected to
clear southern WI late this evening, with some potential for
post frontal sprinkles to linger until dawn on Tuesday amid
lighter northeast winds.

CMiller

&&

.MARINE...
Issued 211 PM CDT Mon May 4 2026

Gusty southerly to southwesterly winds will persist this
afternoon ahead of an approaching cold front. A Gale Warning
remains in effect over the northern third of the lake through 4pm
CDT this afternoon.

This cold front is in association with low pressure over north
central Ontario, which will track northeast toward James Bay
through Tuesday. As this occurs, the cold front will sink
southeast over Lake Michigan through this afternoon and clear
the lake tonight, ending gales and changing winds to
northwesterly. Some scattered storms may occur along the front,
supportive of gusty winds.

West to northwest winds then persist through tonight through the
first half of Tuesday, with winds becoming light and variable
Tuesday afternoon into Wednesday morning as a weak surface ridge
passes over the lake. Similar winds are expected Wednesday, before
southerly return Thursday.

CMiller

&&

.FIRE WEATHER...
Issued 140 AM CDT Mon May 4 2026

Warm, dry and breezy conditions today will lead to an elevated
concern for fire weather across southern WI. Given recent rains
and green up largely being complete, it is not thought that fuels
are at a near critical level but the weather conditions are. Highs
in the upper 70s, relative humidities falling to the 20-30 percent
range and sustained winds around 15-20 mph with gusts to 40 mph
all contribute to the increased fire weather concerns. The
showers and storms potential later today may raise dewpoints in
those areas but those chances remain uncertain and at best
scattered and thus the risk will persist for all of southern WI.

Additional dry conditions may occur again tomorrow, owing
primarily low min RH values between 25 and 35%, though
temperatures will be cooler in the 50s, winds will be lighter,
and there will be more cloud cover present.

Kuroski and CMiller

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ563 until 4 PM Monday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM
     Monday.

&&

$$

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