textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Scattered thunderstorms are expected to shift eastward through the area this evening, exiting to the east around midnight. These storms will pose a risk of hail and strong winds mainly along and west of I-39 into this evening.

- Cooler temperatures are expected Tuesday through the end of the week. There is a less than 20 percent chance of a freeze Thursday night and a 20 to 40 percent chance of a freeze Friday night.

UPDATE

Issued 723 PM CDT Mon Apr 27 2026

A scattered area of storms in southwest Wisconsin is expected to shift eastward into south central Wisconsin, along the advancing cold front. These storms should still pose a risk for hail up to one inch in diameter and strong winds into this evening, mainly west of I-39. There is still northeast 0 to 3 km shear vectors of 35 to 40 knots into this evening, with up to 1000 J/kg of MLCAPE.

So, any northeastward surge in any of these storms could pose a strong wind risk. As daytime heating is lost and instability weakens later this evening, the storms may also gradually weaken as they shift into east central and southeast Wisconsin. Will still watch these storms closely through the evening hours. This activity should shift east of the area around midnight.

There should be some low clouds that develop later this evening and overnight, as gusty west winds develop behind the cold front. Also, some fog may develop over Lake Michigan, but should remain east of Sheboygan, Milwaukee and Kenosha. They may linger into Tuesday morning, before scattering out in the afternoon with west northwest winds. Lows tonight should drop into the middle to upper 40s, with highs Tuesday around 60 degrees.

Wood

SHORT TERM

Issued 140 PM CDT Mon Apr 27 2026

Rest of the This Afternoon and Tonight:

Warm advection band of rain and embedded thunder continues to move to the northeast. On the back edge of this rain, winds are still gusting to between 40 and 50 mph. Latest observations are closer to 40 mph. The back edge of this area of rain should exit to the east/northeast between 2 and 230 PM.

Attention then focuses to the west where some clearing has occurred over Iowa and a cumulus field has developed. A narrow band of scattered storms is starting to develop across portions of central to north central Iowa in an axis of increasing CAPE. Other narrow low level convergence zones exist across eastern Iowa, which should provide focus for additional development. With some daytime heating to the west, surface based CAPE will approach 1500 J/kg, mixed layer a bit lower at 1000 J/kg. This nose of instability will enter southwestern WI during the mid/late afternoon as the aforementioned boundaries and convergent zones approach.

Scattered storms will pose a marginally severe hail threat and a localized downburst wind threat. The tornado threat hinges on maintaining some sort of backed, southeasterly flow. Guidance indicates as the afternoon progresses, low level winds veer more to the southwest, so the overall tornado risk has decreased, but if a cell can latch on to the southeasterly winds, it has a chance for a brief tornado. The area of main concern with this would be Iowa/Lafayette/Green/southwestern Dane counties.

As the surface low moves steadily to the northeast into this evening, the associated surface boundary will be progressive. Scattered storms will move steadily to the east, exiting over Lake Michigan after 10 PM.

Gagan

LONG TERM

Issued 140 PM CDT Mon Apr 27 2026

Tuesday through Monday:

Cooler, drier conditions will build into the region Tuesday, though low clouds will hang on for at least the morning. Northwest flow aloft begins to take hold and will send a few embedded shortwaves our way. Timing these waves will be the trick, but blurring ones eyes there is a chance for showers Wednesday evening into Thursday morning.

Surface high pressure builds in the region for the end of the week and at least the first portion of the weekend. Will need to keep a close eye on frost/freeze potential Thursday and Friday nights. Right now, the better opportunity for a freeze looks to be Friday night.

Northwest flow aloft will remain in control this weekend into early next week. Another shortwave passage is progged for the latter half of the weekend, with the next chance for rain slated for late Sunday into Monday morning.

Overall, this is a cooler and drier pattern for the next week or so. The GEFS CIPS analogs maintain a cooler than average pattern and temperatures will be at or below average for the next week or so. Rainfall chances will be there every 2-3 days, but should be quick hitters in this fast flow.

Gagan

AVIATION

Issued 723 PM CDT Mon Apr 27 2026

A scattered area of storms in southwest Wisconsin is expected to shift eastward into south central Wisconsin, along the advancing cold front. These storms should still pose a risk for hail up to one inch in diameter and strong winds into this evening, mainly west of I-39. These may affect Madison and Janesville at times through 03Z Tuesday. May see locally reduced ceilings and visibility values with any storms.

As daytime heating is lost and instability weakens later this evening, the storms may also gradually weaken as they shift into east central and southeast Wisconsin. Thus, this activity may affect Sheboygan, Waukesha, Milwaukee and Kenosha at times later this evening. This activity should shift east of the area around midnight.

There should be some low clouds with ceilings of 700 to 1500 feet AGL that develop by later this evening and linger overnight, as gusty west winds develop behind the cold front. Also, some fog may develop over Lake Michigan, but should remain east of Sheboygan, Milwaukee and Kenosha. They may linger into Tuesday morning, before scattering out in the afternoon with west northwest winds.

Wood

MARINE

Issued 723 PM CDT Mon Apr 27 2026

The south to southeast gales look to have ended across the southern half of the open waters of Lake Michigan. Thus, the Gale Warning has been allowed to expire for the open waters and nearshore waters of Lake Michigan. A Small Craft Advisory is in effect for the nearshore waters through 1 PM CDT Tuesday for gusty winds and waves between 5 and 8 feet.

High pressure will gradually build into the region Tuesday, and will result in gradually decreasing winds and waves. Light winds and waves between 1 to 2 feet are expected for the rest of the week.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

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