textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Scattered thunderstorms are possible today, particularly in the afternoon. A few storms may be severe with large hail and damaging winds the main concerns.

- 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.

- Thunderstorms are possible Thursday afternoon and evening.

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

UPDATE

Issued 707 AM CDT Tue Mar 31 2026

A lull in shower/thunderstorm activity will continue into mid- morning. Showers and storms are then expected to fire along the cold front dropping through the area by early afternoon. It still looks like there will be sufficient time for warming and destabilization ahead of the front for the potential for a couple strong to severe storms this afternoon. Hail and wind are the main concerns.

Sharpened the temperature gradient across southern Wisconsin for the upcoming day, as there will be a big drop in temps as the front moves through. The current warm front will likely stay in the vicinity of I-94 into mid-morning, with big changes in temps near the front as it wobbles. Temps will be trick near the lake as well, as the chilly lake will likely contribute to the warm front dipping southward in the east.

DDV

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 707 AM CDT Tue Mar 31 2026

A lull in shower/thunderstorm activity will continue into mid- morning. Showers and storms are then expected to fire along the cold front dropping through the area by early afternoon. It still looks like there will be sufficient time for warming and destabilization ahead of the front for the potential for a couple strong to severe storms this afternoon. Hail and wind are the main concerns.

A warm front will sit west to east roughly along I-94 this morning, with northerly winds north of the front and breezy southerly winds south of the front. The cold front will push through this afternoon, with the northerly winds across the forecast area by late afternoon. Low level wind shear will linger until mid-morning.

Lower ceilings will develop and expand north of the frontal boundary this morning, with widespread 500 to 1500 ft ceilings by the afternoon. Scattered to broken VFR ceilings are then expected behind the cold front late afternoon into the evening except for in the east where lower ceilings could linger into tonight.

DDV

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...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...10 PM Tuesday to 4 AM Friday.