textproduct: Milwaukee/Sullivan

KEY MESSAGES

- More thunderstorms may develop and/or push east northeast into southern portions of the area overnight into early Tuesday morning. There is uncertainty with how much activity may occur. There is a risk for large hail with any severe storms. - Additional showers and storms may occur later Tuesday morning into the afternoon, with exact areas of development depending on early day clouds/rain. A few storms could be severe, with large hail and gusty winds being the primary hazards.

- There is a trend northward with the wintry mix of snow, sleet and freezing rain for Wednesday afternoon into early Thursday afternoon. Areas mainly north of the Highway 18 and Interstate 94 corridor may be affected. Impacts to the Wednesday evening and Thursday morning commutes are possible in these areas.

- Additional chances for rain and a few thunderstorms Friday afternoon into Saturday.

SHORT TERM

Issued 142 AM CDT Tue Mar 31 2026

Overnight through Thursday Night:

There is a lull in the showers and thunderstorms for most of the area, with another area pushing east northeast toward the area from eastern Iowa. This is where the southwesterly low level jet nose is pointing into, where elevated CAPE of 1500 J/kg or more with deep layer bulk shear of 35 to 45 knots. The low level jet may point more into far southwest Wisconsin overnight into early Tuesday morning, which may help generate additional elevated convection.

CAMs have been struggling with the evening activity, and continue to differ with what may occur into early this morning. For now, will keep chances (40 to 50 percent) for showers and thunderstorms into early morning on Tuesday. There is still a risk for large hail up to one inch in diameter with any severe storms, as mid-level lapse rates remain steep.

If scattered shower and storm activity lingers into the rest of Tuesday morning, this could limit instability and further convective development with the cold frontal passage later Tuesday morning into the afternoon. There is fairly robust low level frontogenesis response with the front, so there may still be at least showers that occur. The thunderstorm and severe chances will hinge on any daytime heating to occur, so uncertainty remains for what may happen during this period. Kept 60 to 80 percent chances for showers going with the frontal passage, but thunder chances were kept in the 30 to 40 percent range for now.

Temperatures will still be mild ahead of the front in far southern parts of the area, where south to southwest winds can develop. Much cooler temperatures are expected to linger to the north and northeast, where winds are more north to northeast. After the front moves through, gusty north to northeast winds should bring much cooler temperatures to the rest of the area Tuesday night into Wednesday.

Models seem to be trending further to the northwest with the surface low track for Wednesday into Thursday, with the low possibly now tracking either through or to the northwest of the area. Ensembles are more through the area, though they may trend like the deterministic models in later runs. Thus, this would trend the snow, sleet and freezing rain potential further north Wednesday afternoon into early Thursday afternoon. This could end up in mainly northern portions of the forecast area or even more to the north if this trend continues.

For now, kept the wintry mix north of the Highway 18 and Interstate 94 corridor for now. There may be travel impacts wherever this sets up, so it will be monitored and eventually messaged when more confidence in the location of the wintry mix is found.

This system also may bring locally heavy rainfall to the area, as ensembles have been showing 50 percent or higher probability for amounts above 1.00 inch over northwest parts of the area. If the northward trend continues, this may shift northward as well. There may be some elevated thunderstorms that occur Wednesday night and more surface-based storms for Thursday, if milder temperatures work into the area. Too early to tell if any stronger storms may occur with this system.

Wood

LONG TERM

Issued 142 AM CDT Tue Mar 31 2026

Friday through Monday:

Another low pressure system should shift northeast through or pass near the area Friday into Friday night, exiting on Saturday. This may bring mainly rain and a few storms to the area if this track holds. Brisk and cooler conditions then work in for Saturday into Sunday, with high pressure working through the region. Ensembles still have fairly high temperature spreads for this period, depending on where the low tracks. So, confidence in the temperature forecast this far out is low at this time.

Wood

AVIATION

Issued 142 AM CDT Tue Mar 31 2026

There is a lull in the showers and thunderstorms for most of the area, with another area pushing east northeast toward the area from eastern Iowa. Additional showers and storms may move east northeast into the area overnight into early Tuesday morning. There is still a risk for large hail up to one inch in diameter with any severe storms.

If scattered shower and storm activity lingers into the rest of Tuesday morning, this could limit further storm development with the cold frontal passage later Tuesday morning into the afternoon. There may still be at least showers that occur. The thunderstorm and any severe chances will hinge on any daytime heating to occur, so uncertainty remains for what may happen during this period.

South to southwest winds may develop for Madison, Janesville and Kenosha into Tuesday morning, with north to northeast winds for Sheboygan, Waukesha and Milwaukee. Winds may be erratic near the stalled front over the area. After the cold front moves through this afternoon, gusty north to northeast winds should occur and linger into Tuesday night.

Ceilings and visibility should be VFR overnight, except locally MVFR/IFR in any storms. Ceilings should drop to around 1000 feet AGL or lower at times this morning, lingering until the cold front moves through this afternoon. Ceilings may remain around 2500 feet AGL for a time after the frontal passage, before rising above 3500 feet AGL Tuesday night.

Wood

MARINE

Issued 142 AM CDT Tue Mar 31 2026

A frontal zone should sag south to around a Milwaukee Wisconsin to Whitehall Michigan line into the overnight hours, with both wind flows becoming stronger over the far north and far south portions of the lake. Some 20 to 30 knot gusts may occur over the northern third and southern third of the lake. Showers and thunderstorms may occur into Tuesday across the lake, with a few stronger storms possible at times (particularly near the frontal boundary). Large hail would be the primary hazard with any stronger storms.

The boundary will sag further south as a cold front Tuesday afternoon, focusing lingering shower and thunderstorm activity over southern Lake Michigan, before washing it away later Tuesday. Gusty north winds will build in behind the front Tuesday evening into Wednesday, with gusts up to 30 knots. Winds should then veer northeast through Wednesday.

High pressure around 30.7 inches will shift from Ontario to Quebec through the late week time period, as low pressure around 29.5 inches approaches from the southwest, allowing winds to shift east northeast. Will need to watch for gale force gusts later this week, particularly Thursday, as the low pressure system approaches the lake.

Winds and waves may reach Small Craft Advisory levels for the nearshore waters Tuesday night, and may continue at times Wednesday into Saturday.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.