textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Scattered thunderstorms build into the region from southwest to northeast this evening, continuing into tonight. A few stronger storms will be capable of large hail. The recent rain with an additional half inch to inch tonight may cause localized flooding through Saturday morning.

- Seasonal temps and dry weather Sunday into early next week.

UPDATE

Issued 732 PM CDT Fri Apr 3 2026

Scattered showers with isolated embedded thunderstorms have developed along the 850 mb warm front this evening, and are expected to generally stay isolated to scattered for the next few hours. Minimal impacts expected during this time frame. As the parent low propagates northeastward, expecting more widespread storms to develop. With continued WAA at 850-700 mb through this period, MUCAPE values still expected to build ahead of the low. Therefore, cannot rule out isolated severe hail (up to 1 inch in diameter, or quarter sized). Still expecting localized flooding to be a concern within these storms as well, especially areas that see multiple rounds tonight.

MH

SHORT TERM

Issued 215 PM CDT Fri Apr 3 2026

Rest of Today through Monday:

Continuing to monitor the complex of thunderstorms inbound from northeastern Iowa. The southern flank of this storm complex is in a more favorable environment (due to lower antecedent cloud cover and a delayed arrival of marine air from Lake Michigan) and is holding it's strength, while the northern portions (which will track through our region over the next few hours) is breaking down for the time being. As we can see on Radar closer to central Iowa, additional thunderstorm complexes will move in behind it, progressing northeastward through the region later this afternoon into this evening as MUCAPE values build closer to 700 joules (values up to around 1,000 joules possible). As this occurs, the marine airmass entering southern WI on east to northeasterly surface winds will deepen, keeping the lower atmosphere stable and removing the tornado / damaging wind threat, leaving just a hail threat (level 1 out of 5 'Marginal' severe threat) for our region later today into tonight. CAMs resolve these more 'robust' thunderstorms pushing northeastward into the region from 7 PM to Midnight, with a more organized thunderstorm complex / line of storms possible as the LLJ strengthens over southern WI between 11 PM tonight and 5 AM Saturday (though MUCAPE will be almost completely depleted by 4 AM, leaving mainly rain showers after that). 10-50% chances for scattered light rain showers then linger post-dawn Saturday morning as an occlusion passes overhead, with breezy west winds arriving behind it (gusts upwards of 30 MPH) late Saturday morning into Saturday afternoon.

Dry and seasonal weather expected for Sunday, a modest northwest breeze and highs around 50 degrees. A chance for sprinkles of rain Sunday evening / night with a passing 500mb shortwave trough, only a 15% chance of measurable (~0.01") rainfall with that. Strong high pressure dives southeastward into Minnesota on Monday, allowing the northwest breeze to continue (or perhaps strengthen slightly) with high temperatures in the mid to upper 40s as a result of this cold advection and continued dry conditions (precip chances 10% or less).

Sheppard

LONG TERM

Issued 200 PM CDT Fri Apr 3 2026

Monday night through Friday:

The broad 500 mb trough to the east of the region will shift further east Monday night into Tuesday, with nearly zonal flow in its wake. High pressure is expected to shift east southeast across and to the east of the region during this time. Temperatures should be a little below seasonal normal values, with winds Tuesday off of Lake Michigan.

Warm air advection then develops with increasing south winds across the area Tuesday night into Wednesday night. This should bring milder and more moist air into the area during this period. A cold front may then shift east through the area later Wednesday night into early Thursday morning, though there is some uncertainty with the ensembles with the timing of this front.

The Tuesday night into Wednesday night period will have chances (mainly 30 to 50 percent) for precipitation. Temperature profiles from forecast soundings may support a light rain and light snow mix Tuesday night, if the airmass can saturate enough. It would become mainly rain on Wednesday into Wednesday night/early Thursday.

The frontal boundary may stall over or south of the area for a time Thursday, before sagging southward Thursday night into Friday. There remains uncertainty with ensembles on where this boundary may go during this period. Ensemble members are generally wet during this period, so will leave the 30 to 60 percent chances for precipitation going for this period.

Temperatures later in the week in the ensembles are generally trending warmer, though the spreads in the possible ranges of temperatures are quite large. Thus, confidence is low in the temperature forecast this far out.

Wood

AVIATION

Issued 732 PM CDT Fri Apr 3 2026

MVFR ceilings this evening will fall into the IFR category by late tonight as low pressure approaches the area. A wave of scattered thunderstorms will progress eastward into late this evening, with a break/more showery activity for a few hours between the main line of thunderstorms moves eastward between 12 AM CDT and 5 AM CDT. Within this line, lightning, reduced visibilities, lowered ceilings, and heavy rain are expected. Isolated large hail up to quarter sized is possible as well. Thunderstorms exit into Lake Michigan early Saturday morning, with isolated rain showers potentially redeveloping Saturday afternoon and evening. Ceilings will improve to MVFR by midday Saturday.

Gusty northeasterly winds will continue through much of tonight, shifting to become westerly behind a cold front Saturday morning into Saturday afternoon. Winds will remain gusty and westerly through Saturday night.

MH

MARINE

Issued 200 PM CDT Fri Apr 3 2026

Northeast winds accelerate later today into tonight as low pressure around 29.7 inches tracks northeastward across Iowa. Showers and thunderstorms overspread the lake into tonight as the low approaches and occludes, with winds turning due east. A few gusts to gale force will be possible tonight, especially towards the northern tip of the lake. The low crosses central portions of Lake Michigan through the daytime hours Saturday, with winds veering southwest behind it.

West to northwest winds then persist through the rest of the weekend, with speeds up to 30 kt and a few gusts to gale force possible at times Saturday night into Sunday morning, followed by slower winds Sunday afternoon and night. A weak low pressure trough around 30.0 inches crossing Lake Superior and northern Lake Michigan will drag a cold front down the lake Monday afternoon. A brief period of brisk northerly winds is expected behind it, diminishing after dawn Tuesday morning. High pressure of 30.6 inches crosses the lake through the daytime hours of Tuesday, with light and variable winds in the afternoon and gusty south winds Tuesday night as the high pushes east of the region. Southerly gales will be possible mid week.

Nearshore Zones: Waves will approach Small Craft levels this evening through Saturday morning due to a northeast breeze, followed by gusty west winds approaching Small Craft levels Saturday afternoon through Sunday morning. An Advisory for one or both of these periods may be needed.

Sheppard

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 1 PM Sunday.