Janesville Wisconsin Weather Forecast Discussion

470
FXUS63 KMKX 080325
AFDMKX
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1025 PM CDT Tue Oct 7 2025
.KEY MESSAGES...
- Widespread frost development expected for areas along and
  northwest of HWY-151 overnight into early Wednesday morning,
  thus a Frost Advisory is in effect.
- Dry and cooler with a return to near normal/seasonal temps
  today through Thursday.
&&
.UPDATE...
Issued 1020 PM CDT Tue Oct 7 2025
Temperatures remain on track this evening, and the Frost
Advisory remains in place as previously issued (for Marquette,
Green Lake, Sauk, and Columbia counties). Some scattered mid-
altitude clouds only briefly interrupted radiational cooling
this evening, and have since pushed south towards the WI/IL
border (and will soon move clear of the region). Winds continue
to decouple, with all areas at 0 to 6 MPH and falling (except
Monroe WI airport up on the hill), so things are looking on
track.
Over Lake Michigan, a slightly different story. The backdoor
cold front (currently along a Manitowoc WI to Pentwater MI line)
is progressing southward, and on the far (east) side of the
lake, is a bit gustier than previously expected (some gusts up
to 29 KT reported, with the northern open waters buoy gusting to
25 KT). For now it`s looking like our nearshore waters will hold
shy of wind criteria for a Small Craft Advisory, though the waves
cut it even closer. A short fused Small Craft Advisory or
Marine Weather Statement cannot be completely ruled out later
tonight if shoreline observations become convincing. If
applicable, waves would subside below the 4 foot criteria by
around 10 AM CDT Wednesday morning and continue to fall through
the day.
Sheppard
&&
.SHORT TERM...
Issued 240 PM CDT Tue Oct 7 2025
Tonight through Wednesday night:
High pressure will build in from the Northern Plains tonight into
Wednesday. Cooler and drier conditions will move in with and ahead
of the high. After the peak of daytime heating ends, temperatures
will quickly fall down into the 30s to 40s overnight. These colder
overnight lows will be due to the clear skies, light winds and high
pressure parked right overhead. A Frost Advisory is in effect for
the northwestern corner of our CWA, which includes, Marquette, Green
Lake, Sauk, and Columbia counties. Those under the frost
advisory will have the best potential for widespread frost as
temperatures drop in to the low 30s. Neighboring areas like far
western Fond du Lac, northwest Dodge, northern Dane and
northern Iowa counties may see some frost as well, but it should
be patchier as temperatures are expected to be closer to the
mid 30s. While the frost potential is lower, if you are trying
to get a few more days out of your garden or want to enjoy other
sensitive foliage best to bring them in or cover them tonight.
Lakeshore areas will be the warmest with those overnight lows in
the 40s.
The light winds and dry weather will continue as the high remains
mostly overhead Wednesday. Daytime highs are expected to be in the
low 60s which may feel much colder to some give the mid to upper 80s
we have enjoyed this past weekend. There could be some cloudy skies,
especially from any frictional convergence coming off the lake
(lake induced/effect clouds), but largely expect conditions to
remain dry due to the subsidence under the high. Light and
variable winds will continue into Wednesday night, but
temperatures are not expected to be as low.
Patterson
&&
.LONG TERM...
Issued 240 PM CDT Tue Oct 7 2025
Thursday through Tuesday:
The cooler temperatures will be short lived as southern winds
and WAA kicks back in Thursday as the sfc high moves into the
New England states. High temperatures will return to the upper
60s to mid 70s through the weekend. A weakening low pressure
will follow in behind the exiting low for Thursday into Friday.
This area of low pressure will advance from the Northern Plains
and should drag a cold front across the state late Thursday
night into Friday morning. Models have been trending later with
this frontal passage and that is likely due to the overall
weakening of the system and the front losing some steam. Rain
chances are low around 10-25% with the best chances across
western Wisconsin. There is a secondary feature, a trailing
shortwave that will be moving through the larger upper level
flow. Should the front get delayed further this feature could
merge and slightly strengthen the low and the front. This would
lead to some slightly better chances for light scattered rain.
As things stand now there is a lot of model uncertainty with
timing of both the shortwave and the weakening low/front. So
kept low chance POPs in for the frontal passage. There will be
better chances for rain at the end of the extended as a more
amplified upper level trough will again approach from the
Northern Plains. This trough is expected to move through Sunday
night into Monday.
Patterson
&&
.AVIATION...
Issued 1020 PM CDT Tue Oct 7 2025
Dry weather and VFR thru the TAF period. A few periods of
FEW/SCT clouds (esp towards eastern WI) moving in off of Lake
Michigan at 4,000 ft AGL or higher mid Wednesday, perhaps a few
cirrus clouds at very high altitudes, otherwise perfectly clear
skies.
Winds nearly calm overnight, with some steadier north winds
towards eastern WI later overnight due to a passing backdoor
cold front. A light northeast breeze through the daytime hours
Wednesday.
Sheppard
&&
.MARINE...
Issued 240 PM CDT Tue Oct 7 2025
Breezy north to northwesterly winds across the lake will continue
ahead of an area of high pressure that will build in from the
Plains tonight. This high pressure around 30.4 inches will move
across WI Wednesday and settle over the Great Lakes Region through
the second half of the week. Southerly winds will continue until
Thursday morning when they turn to easterly and eventually
southeasterly by Thursday night. Southerly winds will increase
heading becoming breezy Friday as the high pressure continues to
pull east and low pressure around 29.8 inches advances from the
Northern Plains.
Patterson
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory...WIZ046-WIZ047-WIZ056-WIZ057...3 AM Wednesday
     to 9 AM Wednesday.
LM...None.
&&
$$
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NWS MKX Office Area Forecast Discussion