Marine Weather and Tide Forecast for Lake Geneva, WI

UPDATE
Issued 910 PM CDT Mon Apr 28 2025

A line of thunderstorms, some strong to severe, continues to slowly advance eastward across northern Iowa, southern Minnesota, and northern Wisconsin this evening, along and ahead of a cold front. The overall intensity of this line has decreased over the last few hours, and while the environment ahead of the line remains favorable for strong convection, veering winds and a loss of daytime heating should keep the severe threat more sporadic with this line. Farther to the southwest, more discreet convection has formed west of Des Moines, near the intersection of the dryline and cold front.
Some upscale growth is possible, and this convection may eventually fill in or merge with the main line as the cold front advances further southeast. Bottom line for southern Wisconsin is that the overall severe threat has decreased somewhat, but there will continue to be a risk for a few severe storms heading into the overnight hours. Strong wind gusts will be the dominate threat, though a small tornado and hail risk will continue.

Boxell

SHORT TERM
Issued 310 PM CDT Mon Apr 28 2025

This Afternoon through Tuesday night:

The thoughts on the forecast for today have changed a bit. While the thoughts for this afternoon have not changed as much latest model trends have really kept thinks a bit drier though we are starting to see some weak development across west central WI and southeast MN. This development follows an area of clouds southwest into south central IA. This is the convection we are watching for this afternoon. This remains largely conditional still but the LLJ has been able to at least bring some mild convection thus far so the thought here is that models are not fully capturing the afternoon potential despite it still being conditional as no storms have really gotten going either. But with widespread 40-50 kt effective shear, effective helicity around 200-300 m2/s2 and 0-1km helicity around 150-250 m2/s2 and increasing surface based instability we could start to see storms flourish by the mid to late afternoon. Currently CIN is impacting ongoing storm chances but as we warm up further chances will increase.

Models have started to indicate that late afternoon and early evening surface based CIN may slide in as we cool briefly in the early evening with a surface cap possibly preventing much convection giving us that more conditional environment where any convection would bring primarily a large hail risk. The cap looks likely to be fairly weak though and with mixing could remain uncapped for we cannot rule out other hazards during this timeframe. However, into the early evening models suggest the CIN may actually decrease as the LLJ moves fully overhead possibly allowing for increased mixing. Although this could cause some capping aloft models seem to keep us uncapped and so if we can manage any storms during this period with perhaps forcing from the LLJ we could get some isolated cells and with the environment being very favorable for very strong winds, very large hail and strong tornadoes, especially with strong effective shear (50-60 kts), strong effective helicity (200-300 m2/s2), strong low level helicity (100-200 m2/s2) and plenty of instability to work with (highest values do remain on the western half of the CWA). The early to mid evening threat is more conditional as forcing is very limited thus making it a more uncertain portion of this.

This conditional risk will be right ahead of the least conditional risk with storms looking more likely to track through parts of central and maybe parts of southern WI. We are currently watching convection well to the west in southwest MN and northwest IA as it tracks east. As this swings into WI most models have this area laying down in an east-west fashion and weakening. But this does not appear to make much sense as forcing will no longer be necessary with storms already in place, increasing shear especially in the low levels with the strong LLJ. In addition we should still have plenty of instability around 1000-1500 J/kg and its not a situation where we start to see it cold pool dominated. If this becomes more QLCS-like the tornadic risk will decrease with the primary threat being wind, however if things remain more cellular (like what most models suggest), all hazards will be possible and potentially higher end. While capping may end up playing a role and keep things more elevated due to the strong LLJ, the model environment does not really support that at this time. Despite models weakening convection as it pulls through, outside of near the lake there doesn't seem to be much to suggest storms will weaken, especially with continuing southerly inflow of a warm and moist air mass complete with abundant shear to keep storms organized. This period will bring the greatest chance for severe storms with storms likely focused more toward central WI.

Into Tuesday morning the front will pull through with no storm chances behind the front as colder air and higher pressure starts pushing in behind it. In addition, expect weak ridging bringing mostly zonal flow aloft on Tuesday. We will start to see another shortwave sliding northeast from the Central Plains Tuesday night but likely remaining dry until Wednesday morning.

Kuroski

LONG TERM
Issued 310 PM CDT Mon Apr 28 2025

Wednesday through Monday:

Heading into Wednesday, a trough and shortwaves will be approaching the Great Lakes Region from the desert southwest. The shortwave is expected to be advancing from the Central Plains. The shortwave and larger trough are expected to phase together as they approach the state. The lift generated by these two system will overspread a baroclinic zone just to our south and help generate multiple waves/rounds of showers and storms. Showers and storms are expected to start Wednesday afternoon into Thursday.
There is likely to be break between each wave/round and not everyone in southern Wisconsin will see each wave, but more of those details with some greater certainty are like to develop over the next couple runs of guidance. For the chances for storms, guidance is hinting at things remaining mostly elevated which will help for the few storms we do have. Not much confidence on any stronger storms at this time, but given the elevated instability small hail looks to be the largest concern if any.

Rain and storm chances continue into Thursday as a low pressure system is expected to pass to our south. The environmental set up seems to be a bit weaker on the thunder potential for Thursday.
Southern Wisconsin will be on the northern edge of this system so its likely (roughly 70%) that were dealing with some more stratiform rainfall. This will bring some more widespread rain to the area and give us a few chances for a couple rumbles of thunder.

A few models do try to keep rain going into Friday for southern Wisconsin, but there is less confidence here. POPs top out around 25 to 30% during the day Friday. Some guidance has area of low pressure system or frontal boundary moving through the greater Midwest region. There is so much variation here and thus confidence is lower. The upper level trough should be overhead/exiting which will lead to less lift and pressure rises aloft. So overall not a great set up, but the chances still remain given these few members of guidance.

For the weekend, dry weather and high pressure look to prevail.
This will favor a warming trend heading into the weekend leading to some pleasant weather for the first weekend of May.

Patterson

AVIATION
Issued 910 PM CDT Mon Apr 28 2025

Thunderstorms to the north and west of the terminals will move into the region between about 06z and 09z tonight, with the greatest chances at the more northerly terminals (Madison, Sheboygan). Prevailing MVFR and brief periods of IFR will be possible. Winds tonight will remain very gusty from the south and southwest, with occasional low level wind shear.

The cold front should clear the area on Tuesday morning, with gusty west to northwest winds behind the front.

Boxell

MARINE
Issued 310 PM CDT Mon Apr 28 2025

Southeast winds will continue this afternoon and evening as low pressure tracks through central MN. Winds will become even more gusty later this afternoon, with southerly gales developing across the north half of Lake Michigan. Gales will continue across the north half into Tuesday morning and a Gale Warning is in effect, with a slightly shortened time frame on the back end to 12z rather than 15z. A few gusts to gale force are possible in the south half since winds just above the cool lake water will be gusting to over 40 kt, but gales at the lake level should not be widespread. Small Craft Advisory in effect from now until 21z Tuesday afternoon.

Meanwhile, isolated thunderstorms are possible across the northern half of the open waters later this afternoon, with strong to severe thunderstorms possible across the lake this evening and overnight. The main hazards with these storms would be damaging wind and hail. Low pressure exits into Quebec on Tuesday morning, bringing a cold front southeastward across the open waters, ending thunderstorm potential and bringing westerly winds just below gale force. Winds will diminish quickly Tuesday night as high pressure moves into the region.

Kuroski

MKX WATCHES/WARNINGS/ADVISORIES
WI...None.
LM
Gale Warning
LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ868 until 7 AM Tuesday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 PM Tuesday.