textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Below normal temperatures continue through next weekend. Low temperatures tonight are expected to be near zero away from Lake Michigan.

- A broken line of lake effect snow may wobble onshore tonight, especially right along the shoreline of far southeastern WI. Generally less than 1 inch of snow is expected.

- Light snow is possible again Monday night, mainly north of the I-94 corridor. Expecting around an inch or less in these areas.

- A wintry mix is expected to develop Tuesday evening, with slick spots on area roads possible due to continued cold pavement temperatures. Wintry mix will transition to snow on Wednesday, with uncertainty remaining in total snowfall amounts.

- Additional rounds of snowfall are then possible through the end of the work week, but confidence in exact time frames is much lower.

UPDATE

Issued 1030 PM CST Sun Dec 7 2025

Inland temperatures have dropped 2-5 degrees below prior expectations this evening, with the nearly calm wind, snow cover, and nearly clear skies optimizing radiational cooling. Some thin high-altitude clouds have recently moved in and are putting the brakes on the cooling trend, meanwhile lake effect clouds in far southeastern WI have kept temperatures in check.

Radar has remained clear through this evening, though we are finally seeing some weak returns over Lake Michigan to mark the beginning of lake effect snow potential. Despite the late start (likely arriving after midnight), shoreline areas of far southeastern WI may yet see a trace to 1 inch snow accumulation based on the latest 00z model guidance, though it's not a guarantee. DGZ layer saturation is very small based on forecast soundings, and there's dry air both above and beneath the lake effect clouds. Overall precip chances are in the 40-60% range for the immediate shoreline, much lower towards the western edge of lakeshore counties. The SSW to NNE orientation of the lake effect clouds as seen on Nighttime Microphysics Satellite RGB indicates that areas north of Milwaukee county also have relatively lower precip chances.

The light lake effect snow looks to remain just offshore over Lake Michigan through around 10 AM CST Monday morning before southwest winds kick in and push it further away.

Sheppard

SHORT TERM

Issued 352 PM CST Sun Dec 7 2025

Tonight through Monday night:

A convergence band of lake effect snow is expected to develop this evening as high pressure pushes in strongly from the northern Plains and light easterly winds develop over Lake Michigan. This band is expected to be weak and quick-moving, as plenty of shear aloft is expected (straight easterly winds between surface and 850 mb, and straight westerly above that level), and high pressure bringing in plenty of dry air to entrain within the band. Therefore, expecting only trace to an inch of snowfall with this activity. Snow will meander on and off shore from Kenosha County northward to Ozaukee and perhaps Sheboygan through the overnight hours into Monday morning, exiting offshore again shortly after sunrise. Meanwhile, Arctic high pressure in the remainder of southern Wisconsin will produce low temperatures near zero degrees overnight tonight. Light winds will keep wind chills near the observed temperatures, so no headlines will be needed.

Monday, expect southerly winds to develop ahead of a low pressure system ejecting from the Canadian Prairies. Increasing cloud cover is also expected. However, expecting southerly winds to win out and bring highs in the mid 20s. As low pressure propagates through northern Wisconsin, expecting a trailing frontal boundary to produce at least some snow showers across southern Wisconsin Monday evening through Monday night. Any accumulations currently look to stay north of I-94 as the system has continually trended northward, but will continue to monitor trends and adjust as necessary. Regardless, around an inch or less of accumulations is expected. Snow exits into Tuesday, with winds shifting to westerly behind the front.

MH

LONG TERM

Issued 352 PM CST Sun Dec 7 2025

Tuesday through Sunday:

Low pressure and a shortwave trough will exit the nrn Great Lakes to the east on Tue, but a digging and amplifying shortwave trough will move into WI Tue nt from the nrn Great Plains. There are slight to modest timing and placement differences among the ensemble means of the GFS, ECMWF, and Canadian models, but overall it appears a 987 sfc low will track across central WI into lower MI Tue nt. Low to mid level warm, moist advection will boost temps at the sfc and aloft above freezing for a time, but possibly remaining at or below freezing toward central WI. Thus pcpn type will begin as rain/snow over much of the area becoming rain, then back to light snow toward the end of the event. However, toward central WI it is possible all snow could fall with a few inches of wet snow accumulation. There also would be at least a slight potential for freezing rain as the surface and pavement could remain below freezing for a while even as the air temps warm above freezing. Keep up with the forecast and Winter Wx Advisories may eventually be needed for portions of srn WI.

Brisk nwly winds and cold advection will then take hold on Wed with light snow coming to an end. Nwly flow aloft will continue through the week with additional shortwave troughs in the vicinity of WI bringing 20-30 percent chances for light snow most days. This pattern will also lead to increasingly cold air including the arrival of arctic air late in the week. Upper ridging and a sfc ridge may finally arrive on Sunday.

Gehring

AVIATION

Issued 1020 PM CST Sun Dec 7 2025

Lake effect clouds have built into portions of far southeastern WI, resulting in MVFR ceilings around 2,000 to 2,500 feet. These will persist at broken coverage through much of tonight in these areas, and may briefly wobble deeper into lakeshore counties or far southern Wisconsin (as seen at KJVL recently). We still expect at least a few flurries / light snow showers out of this lake effect activity, with a trace to 1 inch accumulation possible for KENW, KRAC, and KMKE. Generally not expecting this activity to reach other terminals (though KMWC and KSBM are not completely out of the question). TAFs currently afford the lake effect a PROB30 group, but we could upgrade to a TEMPO once we have a healthy signature of it on radar. On the other hand, if it fails to materialize, it could be dropped.

Predominantly VFR ceilings (between 3,500 and 10,000 ft) expected throughout the day Monday, with a southerly breeze gradually building. The next chance for snow is Monday evening / Monday night (20-50%), with trace to 1 inch accumulations possible, mainly north of the I-94 corridor towards east-central WI.

Sheppard

MARINE

Issued 352 PM CST Sun Dec 7 2025

North-northwesterly winds will slowly diminish and becoming light and variable tonight as high pressure builds across the Great Lakes region. The Small Craft Advisory in the southern Wisconsin nearshore regions will therefore end this evening.

High pressure exits Monday afternoon as low pressure tracks through northern Minnesota into Lake Superior, bringing stiff southwesterly winds gusting to gale force across the northern open waters. Condition hazardous to small craft will develop in nearshore regions Monday night and continue through Wednesday. A Gale Watch is in effect late Monday night into early Tuesday morning for the northern half of the open waters. A few gusts near 40 kt are possible over the far northern portions. As low pressure exits, expect winds to shift to become westerly through the day Tuesday.

Another low from the northern Plains will shift winds to south- southwest Tuesday evening, before the low crosses near the center of Lake Michigan and brings strong southwesterly winds to the southern half and light easterly winds to the northern half overnight Tuesday. Winds will all shift to northwesterly as the low exits into Wednesday, with gales possible in the southern half throughout this time frame. Winds gradually diminish Wednesday night, but remain northwesterly through the end of the week. Conditions hazardous for small craft will develop in nearshore regions again Thursday night through Saturday.

MH

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Gale Watch...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567- LMZ868...10 PM Monday to 6 AM Tuesday.