Janesville, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

532
FXUS63 KMKX 302035
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
335 PM CDT Sun Mar 30 2025

.KEY MESSAGES...

- Light rain or drizzle this evening changes to light snow late
  this evening into the overnight but then ends. Less than an
  inch of snowfall accumulation is forecast mainly north of
  Madison and Milwaukee.

- Dry and cool conditions prevail for Mon-Tue then more showers
  and thunderstorms for Tuesday night and Wednesday.

&&

.SHORT TERM...
Issued 335 PM CDT Sun Mar 30 2025

Tonight through Monday night:

Low pressure over srn Lake MI will track to Georgian Bay, Canada
by 06Z Mon with a w-e sfc trough extending westward from it.
Aloft, a shortwave trough currently over IA will move across
srn WI this evening into the early morning hours. The
aforementioned features should maintain areas of light rain and
drizzle into the evening. The main band of 850-600 mb
frontogenesis and snowfall with this system will affect west
central WI to ne WI. Some of this lift and eventual rain
changing to lgt snow will clip srn WI, especially north of
Madison but snow accums will remain minor. There is a little
concern for lgt freezing drizzle or freezing rain well north and
west of the MKE metro area if the troposphere does not saturate
into the dendrite zone before sfc temps drop below freezing.
This remains a very low probability at this time though.

Clearing skies are then expected Mon AM with a cool day to
follow. A sfc ridge will then move across srn WI Mon nt with
another cool night expected.

Gehring

&&

.LONG TERM...
Issued 335 PM CDT Sun Mar 30 2025

Tuesday through Sunday:

High pressure shifting east of the region Tuesday should bring a
period of generally dry conditions with chilly temperatures.

Ensembles suggest a period of strong warm air and moisture
advection later Tuesday night into Wednesday with the low level
jet, with saturated air columns and a resultant high potential
(90 percent plus) for precipitation.

Temperature profiles still look to be cold enough for a rain/snow
mix or all snow in northern portions of the area Tuesday evening,
with a rain/snow mix later Tuesday night. Ensembles continue to
have potential (30 to 60 percent) for at least 1 inch of snowfall
Tuesday night in the northern portions of the area, so will need
to continue to watch this potential. In southern portions of the
area, a quick rain/snow mix to mainly rain is expected Tuesday
night.

SPC has a Marginal Risk for severe storms in southern parts of
the area for Tuesday night. Looking at forecast soundings, there
is weak elevated CAPE during this period, and it is tall and quite
skinny. Effective shear is robust, but would need better elevated
CAPE to be concerned about severe hail. Perhaps some small hail
could occur if an organized storm develops.

Strong low pressure is still depicted by ensemble means to track
well northwest of the forecast area Wednesday afternoon into
Wednesday evening. If this track does occur, the area should be
in the warm sector airmass on Wednesday, which should allow for
warmer temperatures and moisture to push in.

The main question will be if the area can get some sunshine and
subsequent increasing instability, as there should be ample clouds
and rain over the region. There should be some tall, fairly skinny
CAPE despite the rain and clouds. The wind shear on forecast
soundings remains quite strong, given the strength of the pressure
gradient and overall system. If enough CAPE can develop despite
the clouds and rain, strong to severe storms could occur.

For now, continued to have thunder chances (20 to 50 percent)
into most of the area, highest in the south/southeast areas. SPC
continues to have a 15 percent severe risk across a good portion
of the area for Day 5/Wednesday/Wednesday night, so will watch and
see how this system and potential for strong to severe storms
evolves.

The dry slot should move through the region either later
Wednesday afternoon or into Wednesday evening, bringing an end to
any lingering precipitation, including any storms. Breezy winds
are anticipated as well Wednesday into Thursday.

High pressure moving in by Friday should bring dry conditions
back to the area. Kept the fairly dry forecast going into
Saturday. The 500 mb Cluster Analysis then shows some potential
for a deep trough to develop over the region by Sunday or Sunday
night. Temperatures look to be near or a little below seasonal
normals.

Wood

&&

.AVIATION...
Issued 335 PM CDT Sun Mar 30 2025

Cigs below 1 kft will continue this afternoon and evening then
rise to MVFR Cigs during the early morning hours. Areas of fog
and drizzle will prevail this afternoon and evening. The light
rain and drizzle is then expected to change to light snow for a
few hours, especially north of Madison and Milwaukee late this
evening into the overnight. Skies will become mostly clear to
partly cloudy for the morning daylight hours on Monday. VFR
conditions will continue through the day and into Monday night.

Gehring

&&

.MARINE...
Issued 335 PM CDT Sun Mar 30 2025

Low pressure around 29.5 inches will move across southern Lake
Michigan this afternoon, and reach Lake Huron by midnight. Brief
periods of dense fog may occur over the southern portion of the
lake as the low passes. Brisk northeast winds will prevail over
the northern portion of the lake this afternoon, with breezy
southerly winds over the far south. After the low passes, brisk
north to northwest winds will extend from north to south across
the lake tonight and well into Monday. A few gale force gusts are
possible in the north. Lighter winds are then expected Monday
night into Tuesday morning as high pressure moves across the lake.

A Small Craft Advisory is in effect until 1 PM CDT from
Sheboygan to Winthrop Harbor due to brisk northerly winds and
building waves.

Gehring

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 1 PM
     Monday.

&&

$$

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