textproduct: Milwaukee/Sullivan

KEY MESSAGES

- More low clouds and potential for patchy fog this morning in Lake Michigan counties. If patchy fog develops, it may linger into the afternoon hours.

- Highs into the upper 60s well inland today, with low 50s closer to Lake Michigan with onshore winds.

- Widespread showers (80 to 100 percent chances) and scattered thunderstorms return for Monday through Monday night. There is the potential for severe weather with locally heavy rainfall.

- Cooler temps Tuesday through the end of next week, with a frost/freeze potential by the end of the week.

UPDATE

Issued 615 AM CDT Sun Apr 26 2026

Low clouds from Lake Michigan have struggled to make their way inland overnight, but are finally making their way onshore. With sunrise, not anticipating significant fog development, but some patchy fog that does develop close to Lake Michigan would be capable of lingering into the afternoon hours. Otherwise, forecast remains on track with onshore easterly winds keeping temperatures much lower in southeastern Wisconsin than southwestern Wisconsin.

MH

SHORT TERM

Issued 1110 PM CDT Sat Apr 25 2026

Overnight through Sunday night:

High clouds will continue to push through the area overnight into Sunday night. There is the potential for more low stratus and fog to develop overnight into Sunday morning for eastern portions of the area. Light onshore winds and lingering low level moisture under the inversion should help support this development.

One caveat will be the high clouds moving through at times, which may limit the extent of the low clouds and fog. Enough of the short term models are showing the low clouds and fog pushing onshore to leave it in the forecast overnight into Sunday morning for now. There is some potential for this to linger into the afternoon as well. Cannot rule out locally dense fog moving onshore, though this potential will need to be monitored.

Otherwise, easterly winds today, with more northeast winds near the lake, are expected. Mild highs into the upper 60s are expected well inland, with 50s closer to Lake Michigan.

East southeast winds should gradually increase Sunday night, as the precipitation ahead of the next low pressure system approaches from the west. Kept gradually increasing PoPs (20 to 40 percent in the western parts of the area) for later Sunday night.

Wood

LONG TERM

Issued 1110 PM CDT Sat Apr 25 2026

Monday and Monday night:

An upper trough crossing the Colorado Rockies will take on a negative tilt over the Plains Monday morning as it aligns with a coupled upper jet. As the system approaches, the low level jet will actually increase over the state of WI during the day Monday. There is still some degree of uncertainty in the strength of the cyclogenesis, which will affect the track of the surface low and also the placement of the warm front. The other factor for the warm frontal location is where any morning convection tracks.

As the mid level vorticity and low level jet push into southwest WI early Monday morning, the upstream storms have a chance to keep hold together. Depending on the speed of the system, these anticipated early morning storms could zip northward from central/eastern IA into central WI OR cross southern WI. A slower solution would keep srn WI in a more unstable environment.

With persistent warm air advection and vorticity advection, scattered thunderstorms will be likely for much of the day. Strong 0-3km and 0-6km shear will be high (southwest 35-45kt for 0-3 and even stronger bulk) due to the southeast winds at the surface and south winds just above it. Steepening mid level lapse rates with the mid level trough will help to increase the CAPE values in the afternoon, but they should only top out around 1000 j/kg. A high- shear-low-cape environment is conducive for damaging winds and brief spin-up tornadoes (QLCS tornadoes), depending on how organized and strong the storms get. The higher 925mb theta-e values just south of the IL border which would favor the more widespread convection to focus there.

It will be a windy day Monday, breezy out of the southeast with gusts over 30 mph. High temperatures will depend on how much sunshine and how far north the warm front can push, but around 70 inland from Lake Michigan is a reasonable forecast at this time. By mid Monday evening, the surface low and area of thunderstorms should be clear of southeast WI. However, the upper trough will still be positioned over MN, so the chance of showers and maybe a few rumbles of thunder will linger in southern WI until the trough clears Tuesday morning. Repeated rounds of storms will bring a risk for greater than 2 inches of rain, and the location with the higher risk (20 to 30%) is south central and southeast WI at this time.

With the system becoming slightly occluded during the afternoon/evening Monday, the severe chances for southern WI seem a little disjointed and the strongest convection may end up splitting around the majority of our area. That said, shifts in the system's evolution are still a very real possibility. The CIPS analogs are showing similar scenarios to other severe outbreaks, but looking at those individual cases reveals a more negatively tilted upper trough that is not occluding when it crosses the Upper Midwest. Keep up with the forecast.

Tuesday through Friday:

Gusty west winds will ensue Tuesday behind the front and highs should only reach around 60. We are going to shift into a cooler weather pattern for the week with highs in the upper 50s to around 60 Wed-Fri. This is due to an upper trough lingering over eastern Canada and the northeast states with WI in northwest flow. Precip chances will be minimal during this time.

Cronce

AVIATION

Issued 615 AM CDT Sun Apr 26 2026

VFR conditions remain across interior portions of southern Wisconsin, with IFR ceilings developing across Lakeshore terminals. IFR conditions are expected to last along the lakeshore for the next few hours before gradually lifting and scattering out into midday for a return to VFR. Patchy fog is still possible, but becoming less likely. Easterly winds are expected to increase through today, but generally remain steady between 10 and 12 kt during the afternoon. Overnight tonight, winds will shift to become southeasterly and become gusty around 25 kt. Although winds will remain onshore, gusty conditions are expected to keep any developing marine clouds at MVFR or above. A line of rain and storms will develop across southwestern Wisconsin Monday morning, progressing eastward through midday and lowering visibilities and ceilings.

MH

MARINE

Issued 1110 PM CDT Sat Apr 25 2026

East to northeast winds are expected to develop overnight into Sunday, as high pressure around 30.2 inches shifts eastward into southeast Ontario. Low pressure around 29.4 inches is then expected to move from northeast Kansas early Monday to Lake Superior by early Tuesday morning. Winds will increase Monday into Monday night out of the south to southeast ahead of the low.

The cooler lake temperatures may limit widespread gales across the lake during this time, but a few gale force gusts are possible. Breezy west to northwest winds will then develop behind the departing low by later Tuesday. Lighter winds should then occur into the rest of next week.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

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