textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Areas of fog possible tonight, particularly across the southern half of the area.

- Well above normal temps will continue through Friday with the exception of near the lake on Wednesday.

- Next chances (60-80%) for showers and thunderstorms late Thursday night and Friday, then again early next week.

UPDATE

Issued 515 PM CDT Tue Apr 21 2026

Currently centered near International Falls, MN, high pressure will continue to work east across Lake Superior this evening and tonight. The passing high will encourage mostly clear skies and light/variable surface winds through the overnight hours tonight, with sufficient low level moisture in place to support some areas of fog through the predawn hours. Currently anticipating the best fog potential to reside over the southern half of the area, where low level moisture advection has continued through this afternoon & an encroaching surface boundary will promote light to even calm winds. Have continued mentions in the weather grids over this part of the area. Whether or not any fog will become dense remains uncertain, with trends being monitored through the overnight period.

Quigley

SHORT TERM

Issued 307 PM CDT Tue Apr 21 2026

Tonight through Thursday:

The showers and storms have shifted to the south and east as the low to mid level thermal ridge and moisture ridge moves away. A weak and decaying, dry cold front will then pass from north to south across the region from late this afternoon into the evening. Much later at night, areas of fog may form over far srn WI as the front stalls over nrn IL.

High pressure over Ontario and the nrn Great Lakes Wed AM will shift toward the lower Great Lakes, while upper ridging moves into the Upper MS River Valley. Ely winds will become ssely with warm advection beginning once again. High temps will range from 50s at the Lake MI beaches to middle to upper 70s over south central WI. The sly winds will continue to bring warm temps into Thu as a n-s sfc trough and cold front moves ewd across the Great Plains. High temps will be near 80F.

Gehring

LONG TERM

Issued 307 PM CDT Tue Apr 21 2026

Thursday night through Tuesday:

For late Thu nt and Fri a shortwave trough will lift from the central Great Plains into WI, while the cold front slowly passes. Thus 60-80 percent chances for showers and scattered storms are forecast. A weak high pressure area will then pass on Sat followed by increasing sely winds and warm advection for Sunday ahead of cyclogenesis over the central Great Plains.

The low pressure area and associated shortwave trough is then expected to lift newd into WI on Mon, with another round (50-60 percent) of showers and storms.

Gehring

AVIATION

Issued 515 PM CDT Tue Apr 21 2026

Primarily VFR flight categories prevail through the period as high pressure currently centered near Lake Superior migrates east toward Lake Huron. The passing high will lead to mostly clear skies through Wednesday morning, with FEW-SCT upper level clouds gradually moving in on Wednesday afternoon. The clear skies will combine with light & variable winds tonight to support areas of fog, particularly across the southern half of the region. Have inserted prevailing mentions in the 00Z update at all terminals along and south of I-94, and will continue to monitor trends further north. Whether or not dense fog will occur remains uncertain, with trends being monitored through the evening and overnight hours. Any areas of BR/FG should quickly dissipate following sunrise Wednesday morning. Light and variable winds will trend east-southeasterly during the day Wednesday.

Quigley

MARINE

Issued 307 PM CDT Tue Apr 21 2026

Light to modest south winds will shift to light north to northeasterly tonight, as a weak cold front passes and high pressure moves across Ontario and the northern Great Lakes. Scattered strong thunderstorms will affect far southern Lake Michigan this afternoon.

The high over the northern Great Lakes will then shift to the lower Great Lakes on Wednesday. Light northeast to east winds on Wednesday will then become southeast Wednesday night and increase Thursday into Friday, as strong low pressure around 29.2 inches develops in the northern Plains.

A Small Craft Advisory may be needed north of North Point Lighthouse from late Thursday afternoon into Friday morning.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

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