textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Patchy dense fog (1/4 mile or less) is expected west of Madison this morning, with fog and visibilities as low as 1 mile developing elsewhere. Fog will lift this afternoon, but may return late tonight.

- Warm temperatures and rain on Sunday will transition rapidly to snow and temperatures below freezing Sunday night, with flash freeze possible. Expect widespread accumulations between a trace and an inch, but areas near central Wisconsin may see as much as 3 inches.

- Polar air returns Sunday night and continues through the end of next week, with temperatures remaining at or below normal. - Northwest gales are likely for all of Lake Michigan Sunday night into Monday evening.

SHORT TERM

Issued 435 AM CST Fri Dec 26 2025

Today through Saturday:

Low clouds and rain showers will continue through early this morning, with fog developing behind the rain showers shortly before sunrise and continuing into midday. Fog density upstream has been in the 1/2 to 1/4 mile visibility range, but expecting visibilities to improve shortly after sunrise to around 1 mile. Still potential for areas of dense fog, however, and conditions will be monitored for any developing hazards. Fog will likely lift briefly this afternoon.

Low clouds will linger throughout the afternoon, preventing temperatures from rising higher than the mid-40s in the south and the upper 30s in the north, even with a warm airmass in place. A cold front will sweep through the region this afternoon, bringing a return to the mid-30s during the afternoon to evening hours. Temperatures will stabilize overnight with low clouds continuing, keeping lows in the mid-30s. Fog may build back down to the surface tonight as well, as winds diminish under a ridge of weak high pressure.

Saturday, expect winds to shift to southeasterly once again as low pressure develops in the lee of the central Rockies between a northern shortwave ejecting southeastward from Canada and a developing southern shortwave from the remnants of an earlier atmospheric river in California. As these shortwaves interact, expecting low pressure to develop and begin to propagate northeastward into Saturday night. Expecting highs in the mid-40s under the continual surface WAA, even as skies remain generally overcast.

MH

LONG TERM

Issued 435 AM CST Fri Dec 26 2025

Saturday night through Thursday:

As low pressure ejects from the Rockies into the Plains on Saturday night, expecting southeasterly winds to continue, with low temperatures remaining in the upper 30s to low 40s. Low pressure will make its closest approach on Sunday, although model solutions still diverge on the strength and placement of the low center due to the uncertainties of how the northern shortwave with phase with the southern shortwave (which still looks to become the dominant one). Still, expecting widespread rainfall (~60% chances) as the low makes its closest approach as well as high temperatures in the mid to upper 40s. A few spots in far southern Wisconsin may see highs near 50 degrees. During the afternoon to early overnight hours, a strong cold front will drop temperatures rapidly below freezing. This rapid drop in temperatures will also transition any lingering rain to snow. Currently expecting widespread accumulations of a dusting to an inch, with potential for up to 3 inches in central Wisconsin. Regardless of exact amounts, untreated wet surfaces will become slick as temperatures fall overnight. Lows in the mid teens to near 20 degrees are expected.

A few lighter snow showers may linger into Monday morning. Main concern will be gusty northwest winds as low pressure occludes to the northwest. Currently expecting gusts around 35 mph. However, depending on the timing of the low and its intensity as it occludes, higher gusts may become possible. Expect wind chills in the single digits throughout the day, with temperatures in the low 20s. Winds will slowly diminish Monday night as low pressure exits into Quebec.

The next chances for precipitation develop Tuesday as an Alberta clipper rides along the Upper Midwest ridging into northern Wisconsin. Currently expecting the majority of precipitation to remain north of the forecast area (~15% chances in southern Wisconsin).

A shift in the forecast pattern then develops for the latter half of next week as the occluded low over Quebec retrogrades into the Hudson Bay and an atmospheric river impacts British Columbia and the Pacific Northwest. Expecting the combination of these two major weather systems to bring in progressively colder air from the Canadian Prairies, with highs in the teens by Thursday.

MH

AVIATION

Issued 435 AM CST Fri Dec 26 2025

IFR ceilings are expected across the entirety of southern Wisconsin by sunrise, with some pockets of LIFR visibilities and ceilings, especially in southwestern Wisconsin and along the IL/WI border. Patchy dense fog is expected in southwestern Wisconsin as rainfall ends, with visibilities in the 1-3 SM range elsewhere. Visibilities will improve midday, but expecting IFR ceilings to continue with only minor improvements this afternoon. Tonight, fog may build back down to the surface during the late overnight hours, lifting into Saturday morning.

Southeasterly winds will become light and variable this morning, then northwesterly this afternoon as a cold front moves through the region. Light and variable winds are expected again overnight, before becoming southeasterly again Saturday morning.

MH

MARINE

Issued 435 AM CST Fri Dec 26 2025

Low pressure over the Upper Mississippi Valley to western Lake Superior will continue to progress eastward today, bringing modest southeasterly winds to Lake Michigan this morning, transitioning to light and variable this afternoon before a cold front shifts winds to northwesterly this evening into tonight. High pressure builds in briefly tonight into Saturday, with light and variable winds again.

Modest southeast winds will then return by midday Saturday and continue through Sunday morning as low pressure develops over the central Plains. Low pressure deepens Saturday evening and crosses southern Lake Michigan, bringing gusty northwesterly winds up to gale force. The low will continue to deepen throughout Monday as it moves eastward. Confidence is high in gale force winds through Monday night across the open waters, with brisk northwest winds then continuing through Tuesday. Much colder air will also bring moderate freezing spray throughout the gale time frame.

MH

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 2 PM Friday.