Janesville, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

201
FXUS63 KMKX 191836
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
136 PM CDT Thu Mar 19 2026

.KEY MESSAGES...

- Gradual warming trend expected through the Saturday.

- Next chances for precipitation primarily across central
  Wisconsin (15 to 30 percent) Saturday night into Sunday.

&&

.SHORT TERM...
Issued 135 PM CDT Thu Mar 19 2026

Tonight through Saturday:

Temperatures have quickly risen to 50 degrees away from Lake
Michigan, with temperatures in the 40s across central Wisconsin
(more snowpack) and near Lake Michigan (light lake breeze).
Expecting mostly sunny skies to prevail, with highs a few
degrees above current temperatures as spring sunshine continues
for the next few hours.

Tonight, temperatures will fall into the mid to upper 30s. This
will be near dewpoints with very light winds under high
pressure. This may lead to patchy fog tonight. However, a northern
Wisconsin low pressure system will bring increasing southwesterly
winds during the late overnight hours into Friday morning,
scrubbing out fog and allowing for a period of low stratus.
Winds shift to become northwesterly Friday morning, bringing
additional low clouds in.

Friday afternoon, clouds will scatter out across southwestern to
far southern Wisconsin as winds diminish, allowing for
temperatures to rise into the upper 50s to near 60 degrees.
Elsewhere, where cloud cover lingers, expect highs in the upper
40s to low 50s.

Additional shortwaves traverse southern Canada and the northern
Great Lakes region Friday night and Saturday, keeping winds
southerly and temperatures warm. Expect Friday night lows in the
upper 30s and Saturday highs in the 50s near Lake Michigan and
central Wisconsin, the 60s in the majority of southern
Wisconsin, and even the low 70s possible in far southwestern
Wisconsin.

MH

&&

.LONG TERM...
Issued 135 PM CDT Thu Mar 19 2026

Saturday night through Thursday:

Ensemble and deterministic model guidance suggests several clipper
systems will progress west to east across the region through this
time period, though with much of the QPF (precipitation) passing
well north of the region. The first could pass anytime from
Saturday night through the daytime hours Sunday, likely only
lasting a small fraction of that window. Our forecast calls for
15-25% precip chances with it (highest towards east-central WI),
and based off the antecedent warmth, this would be all rain. On
the back side of this system (depending on it`s track, which is
widely disputed amongst ensembles), we wouldn`t be surprised to
see a trace of flurries / freezing drizzle in the cold conveyor,
though the odds of any measurable / impactful precip are 15% or
less at this time. North to northeasterly flow on Sunday will
advect some cooler air into the region (particularly along the
Lake MI shoreline), there`s a wide spread in the exact temperature
values (with ~50 degree inland highs as the median), but the main
story will be `much cooler than Saturday`. As CAA continues into
Sunday night, ensemble temperature IQRs for minimum temperature
fall to the mid to upper 20s.

The rest of the clipper systems through this period pass north of
our region, allowing temperatures to gradually moderate upwards.
Predominantly dry weather expected through the period, with the
majority of model QPF missing us to the north once again.
Generally, the earliest we could see a more organized low pressure
system (with higher precip chances) would be late next week
(Thursday and onwards) based on ensemble guidance.

Sheppard

&&

.AVIATION...
Issued 135 PM CDT Thu Mar 19 2026

VFR conditions prevail through the remainder of today and this
evening under high pressure with light and variable winds.
Overnight, patchy fog is expected to develop. A cold front will
shift winds to southwesterly late tonight and northwesterly
into Friday morning, clearing out any remaining fog, but
bringing in a wave of 1000 ft ceilings. Some models are
indicating potential for even lower ceilings in the IFR range.
Winds will remain northwesterly through Friday evening. Ceilings
will begin to scatter out into Friday evening.

MH

&&

.MARINE...
Issued 135 PM CDT Thu Mar 19 2026

High pressure of 30.2 inches will keep winds light and variable
through this evening, with southeasterly winds developing late
tonight as low pressure around 29.7 inches progresses east into
Lake Superior. Winds will shift to northwesterly as low pressure
exits eastward Friday morning. Winds shift northeasterly as high
pressure of 30.2 inches builds into Ontario Friday night. Low
pressure then develops in the lee of the Wyoming Rockies
Saturday morning, shifting winds to southeasterly and allowing
them to increase as low pressure progresses eastward Saturday
night. Low pressure crosses northern Illinois into southern
Lower Michigan as it deepens to 29.4 inches, leading to
northerly winds backing to northwesterly Sunday into Sunday
night. Gales are possible during this timeframe. High pressure
with lighter winds then dominate on Monday.

MH

&&

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

$$

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