textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Light wintry mix of freezing rain, sleet, and snow near & especially north of I-94 and US-18 this evening (~4-10 PM). A light glaze of ice can't be ruled out on elevated & untreated surfaces.

- Patchy freezing fog & possible early Monday morning.

- Additional chances (~30-50%) for mostly rain Tuesday. Some precip could start as rain-snow mix or freezing drizzle.

- Temperatures trending well above normal Wednesday through Thursday.

- Becoming colder & more active Friday through Sunday, with multiple chances (~20-40%) for rain and snow.

UPDATE

Issued 1006 PM CST Sun Jan 4 2026

Most of the freezing drizzle/wintry mix has ended for tonight with the WAA wave pushing east. Clearing is currently working in from the west and should spread over most of the CWA through the early morning hours, which may allow for slightly lower overnight lows. Have tweaked them down a bit to account for this.

Freezing fog does appear possible tonight as CAM soundings show shallow moisture trapped near the surface in southwest to south central WI.

CMiller

SHORT TERM

Issued 320 PM CST Sun Jan 4 2026

Tonight and Monday:

Synopsis/Mesoanalysis: Water vapor imagery shows a shortwave trough near the South Dakota-Minnesota border early this afternoon. Precipitation is ongoing in advance of the wave, with low level warm advection helping to drive a mix of wintry precip types at upstream stations. Expect the southern edge of this area of precip to clip southern Wisconsin this evening, with a mix of light freezing drizzle, sleet, and snow being favored given continued warm advection in the lower part of the column. Best precipitation potential is to the north of I-94 and US-18, where the strongest warm advection-driven ascent will reside. A light glaze of ice is possible in locations experiencing wintry precipitation. The responsible wing of warm advection will push east of the area after midnight, allowing most wintry precip to conclude. Low pressure will move into the Upper Mississippi Valley late tonight, with attendant south-southwest winds maintaining moisture in the lower part of the column. The moist conditions, along with weakening surface winds, could lead to patchy fog development from the predawn hours into early Monday morning. With temperatures below freezing, freezing fog and slick spots are possible. Budget a few extra minutes of time if traveling north this evening or commuting Monday morning. Fog and slick spot potential should improve by late morning Monday.

This Evening: Expect wintry precip to move into the northern half of the area between ~4-10 PM. Anticipate that the majority of precipitation will occur to the north of I-94 and US-18, where increasing warm advection & affiliated isentropic ascent will be greatest. Have thus depicted the highest precip probabilities (~40- 80%) over this part of the area through mid-evening. While weaker in magnitude, model guidance does maintain some weaker lift south/into the I-94 and US-18 Corridors, so did maintain some slight chance to chance (~15-35%) precip probabilities further south into the Madison & Milwaukee metros. Given low level warm advection & an attendant warm nose aloft, do expect that sleet and/or light freezing rain will comprise a good portion of the wintry precip falling this evening. With surface temperatures below freezing, a light glaze of ice is possible on untreated surfaces in areas experiencing precipitation. Best potential will be in central and east-central Wisconsin, where probabilistic guidance shows ~10-30% chances for a glaze (~0.01").

Late Tonight into Monday Morning: Wintry precipitation is expected to taper after midnight as the deeper lift shifts east. Despite waning precip chances, boundary layer conditions will remain moist through the remainder of the overnight period thanks to south- southwest surface flow. With winds forecast to taper during the predawn hours, could thus see some fog development across the region during the late overnight/early morning hours. Peak potential for fog would be between 3-9 AM. With temperatures below freezing, freezing fog and slick spots would be possible in any locations experiencing fog.

Quigley

LONG TERM

Issued 320 PM CST Sun Jan 4 2026

Monday night through Sunday:

Synopsis: A second upper disturbance will cross southern Wisconsin Monday night into Tuesday, bringing chances for mostly rain areawide. Some precipitation could start as freezing drizzle or a light rain-snow mix, with precipitation transitioning to all rain after sunrise on Tuesday. Mostly dry conditions are expected Wednesday through Thursday as high temperatures trend well above normal. Chillier air will gradually work into the region Thursday night into next weekend, along with multiple chances for rain and snow.

Late Monday Night through Tuesday: A second system will bring additional precip chances to the area. Expect an initial round of precipitation to focus along a frontogenesis band in the 700-500 mb layer over northern Wisconsin Monday evening/night, with additional precip filling into central and southern Wisconsin during the predawn hours Tuesday as the upper low approaches/moves overhead. Given potential late overnight onset of precip, temperatures may be cold enough for some rain-snow mix or light freezing drizzle at the very start of precipitation, with a transition to all rain occurring as temperatures climb above freezing following sunrise. Will thus be monitoring trends with this second system, as some minor impacts to the Tuesday morning commute would be possible in any spots seeing wintry precipitation.

Quigley

AVIATION

Issued 1009 PM CST Sun Jan 4 2026

Clearing will continue to push east tonight as the WAA wave and precip quickly push east. With the clearing, and an inversion in place, freezing fog appears possible toward daybreak as sfc winds calm while high pressure approaches from the west. Expect most of this freezing fog to be confine to south central, southwest, and central WI, close to the surface ridge as it moves in.

In the meantime, southwest wind shear to 40 knots is expected into the pre-dawn hours of Monday before subsiding around dawn.

After dawn on Monday, IFR to MVFR clouds return, gradually rising during the late afternoon Monday.

CMiller

MARINE

Issued 320 PM CST Sun Jan 4 2026

1022 mb high pressure is moving east of Lake Michigan this afternoon, resulting in light southeasterly winds. Currently over the northern Great Plains, 1002 mb low pressure will move into the northern Mississippi River Valley this evening, resulting in increasing southerly winds across the waters. Gusts between 25-30 knots will be possible through daybreak Monday. Winds will veer southwesterly and eventually westerly Monday morning as the aforementioned area of low pressure crosses the waters, gradually weakening in the process. Rain-snow mix and freezing drizzle are forecast ahead of the approaching low tonight. Winds will become light and variable Monday afternoon as 1012 mb high pressure moves across Lake Michigan.

Southerly winds will become established Monday night ahead of a new area of 1004 mb low pressure forming in the northern Great Plains. The low will approach and ultimately cross Lake Michigan Tuesday morning, resulting in a west-northwest wind shift by the afternoon hours. Gales are not anticipated during the low's passage. Additional rain and rain-snow mix are forecast Tuesday in affiliation with the low. West to southwest winds will prevail through Wednesday afternoon, turning southerly Wednesday night into Thursday. A cold front will cross the waters Thursday night, bringing north-northeast winds by Friday morning. Rain and snow will accompany the passing cold front Thursday night through Friday.

Waves and southerly winds will increase in nearshore zones this evening as low pressure approaches from the Northern Plains. A Small Craft Advisory remains in effect between 8 PM CST and 6 AM CST Monday in all nearshore zones. Freezing drizzle and rain-snow mix will accompany the approaching low. Winds will quickly subside during the day Monday. Additional Small Craft Advisory conditions are possible Friday night into next weekend.

Quigley

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 6 AM Monday.