Marine Weather and Tide Forecast for Fontana-on-Geneva Lake, WI

UPDATE
Issued 710 PM CDT Fri May 8 2026

Currently monitoring the broken altocumulus clouds drifting southeastward into southern WI, producing some virga visible on radar. Precip chances with this activity this evening / tonight have been reduced to 20% or less, and will likely continue to be reduced as substantial dry air in the PBL / RL wins the battle.
500-700mb lapse rates do steepen later this evening into tonight, so I cannot completely write off an isolated brief spit of rain just yet.

Precip chances for Saturday remain at 20-30%, with a narrow / brief axis of open cellular showers rippling southeastward through southern WI between 10 AM and 7 PM behind a cold front.

Sheppard

SHORT TERM
Issued 137 PM CDT Fri May 8 2026

This afternoon through Monday:

A mild and dry air mass resides over srn WI this afternoon via swly winds ahead of a weak wave of low pressure that will track across Lake Superior tnt. A vorticity maximum over central MN will track across central WI this evening in conjunction with continued low to mid level warm advection over srn WI. A weak cold frontal passage will then follow late tnt. Some of the fcst soundings briefly attempt to saturate the mid levels at times along with some light QPF on the CAMs and deterministic models.
Will forecast 20 percent chances for a brief shower tnt.

On Saturday, another but slightly stronger shortwave trough passage is expected within nwly flow aloft. 850 mb frontogenesis is highlighted a bit on the models over sw WI and another cold frontal passage does occur. Given still, a fairly dry air mass, will keep rain chances at 20-40 percent. Nwly sfc winds and cold advection will bring a return of below normal temps for Sun-Mon. The passage of another shortwave trough on Sunday may eventually result in small shower chances given marginal instability that is expected. High pressure will then follow on Mon. Additional Frost Advisories may be needed for portions of srn WI during this brief cool period.

Gehring

LONG TERM
Issued 137 PM CDT Fri May 8 2026

Monday night through Friday:

A fairly strong shortwave trough and associated wave of low pressure, within nwly flow aloft, will then track across WI on Tue. A well organized swly low level jet and warm, moist advection pattern will bring sufficient moisture and lift for widespread rain and perhaps scattered elevated convection.

High pressure will then follow for Wed nt-Thu AM followed by a jet stream pattern change to quasi-zonal for late next week.
This will bring a return of warm and humid conditions and increasing rain chances.

Gehring

AVIATION
Issued 700 PM CDT Fri May 8 2026

Broken clouds around 10,000 ft are pushing southeastward into southern WI at the moment, bringing some light virga visible on radar. Only forecasting ~15% rain chances through the evening and overnight with this activity, and ceilings / visibility should easily remain VFR. Light SW winds expected overnight.
Stronger WSW winds at the 2,000 ft level (roughly 35kt) will be present for a brief time late tonight (between midnight and 6 AM) and may result in some marginal LLWS. The strength of the shear is below thresholds for inclusion in the TAFs at this time, we will continue to monitor our radar's VAD wind profile for intensity estimates.

A cold front crosses the region Saturday morning, with winds veering NW and becoming gusty behind it by midday. 30% chances for rain showers are forecast late Saturday morning through Saturday afternoon, with the majority of it evaporating before reaching the ground. PROB30 groups have been added to the TAFs, and reflect the expected VFR ceilings with the shower activity.

Sheppard

MARINE
Issued 137 PM CDT Fri May 8 2026

Low pressure around 29.6 inches along the Minnesota and Canadian border this afternoon will move across Lake Superior tonight.
Its cold front will move across Lake Michigan Saturday morning.
Modest to breezy south winds will develop this afternoon before shifting southwest late tonight, and west on Saturday with the cold frontal passage. Another cold front will then shift the winds to northerly Saturday night. High pressure around 30.3 inches is then expected to move from southern Manitoba on Sunday to over Lake Michigan by Monday afternoon. Relatively light and variable winds are expected early next week.

Gehring

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