textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Light snow chances (about 25 to 45 percent) are forecast mainly to the north of Interstate 94 and Highway 18 later tonight through Monday morning, with minimal accumulation and impacts expected.

- Temperatures continue to trend well above normal Tuesday through Christmas Day.

SHORT TERM

Issued 230 PM CST Sun Dec 21 2025

Tonight through Monday night:

Warm air advection develops tonight into Monday, with an area of 850 mb to 700 mb frontogenesis response shifting east northeast through central Wisconsin later tonight into Monday morning. This will bring a period of light snow to central Wisconsin, with the northern portions of the area on the southern edge of any light snow. The 12Z GFS continues to bring measurable QPF/light snow amounts to the far northern and northeastern parts of the area during this period, with the 12Z NAM north of the area and the 12Z ECMWF between them but with lighter QPF. These models have had their respective trends for several model runs now.

Ensemble guidance continues to focus mostly north of the area with most of the measurable QPF/light snow, though does clip the far north and northeast parts of the area with at least a dusting of snowfall. CAMs have some reflectivity moving through, but most of the measurable QPF from those models remains to the north as well.

Forecast soundings from northern parts of the area continue to show a dry layer of air below 850 mb through this period, more so on the NAM/ECMWF/Canadian than the GFS. Even the GFS has some reflection of this dry layer. This will be the negating factor for measurable QPF/light snow in the far northern and northeastern parts of the area.

For now, the 25 to 45 percent PoPs seem reasonable in the northern parts of the area, mainly north of Highway 18 and Interstate 94. A nearly dry forecast remains toward the far southern areas. At this time, it appears that most impacts with the light snow will be north of the area later tonight into Monday morning.

The warm air advection continues Monday afternoon and evening, with forecast soundings showing the low levels saturating and drying out further up. This may allow for any lingering very light snow to become very light rain or drizzle Monday afternoon, as long as surface temperatures stay above freezing. There could be some light freezing drizzle Monday evening, as temperatures drop to near freezing in northern parts of the area. However, kept forecast dry Monday evening until more confidence is gained with the upward motion and moisture in the low levels.

Wood

LONG TERM

Issued 230 PM CST Sun Dec 21 2025

Tuesday through Sunday:

500 mb cluster analyses still support an anomalous ridge to slowly spread east across the region Tuesday into Christmas Day. This will bring well above normal temperatures during this period, with highs around 40 Tuesday and Wednesday rising to the middle 40s Christmas Day. Temperatures should cool down a little but remain above normal into next weekend.

Some warm air advection and low level moisture may bring chances (around 20 percent) for light rain or drizzle Wednesday into Wednesday night. There is a wetter period possible Christmas Day into Thursday night or Friday, depending on the timing and placement of low pressure shifting through the region. Kept the NBM PoPs of 20 to 30 percent generally in place for now.

Wood

AVIATION

Issued 230 PM CST Sun Dec 21 2025

Southwest winds will become south tonight into Monday, then light and southwest Monday night. There should be a period of low level wind shear conditions later tonight into Monday morning, with southwest winds around 35 to 40 knots at 2000 feet AGL.

Middle level clouds should push into the area tonight into Monday morning, lowering to around 6000 feet AGL Monday morning and may lower at all locations to perhaps 2000 feet AGL or less later on Monday.

A period of light snow should occur later tonight into Monday morning, mostly to the north of the area. Sheboygan may see some light snow Monday morning, with a dusting of accumulation at best, so may keep a PROB30 mention in their TAF for now for that period.

There may be some light rain or drizzle Monday afternoon and evening, with perhaps some light freezing drizzle in the evening, if surface temperatures drop to the freezing mark. This is lower probability (less than 20 percent) so will leave this mention out of the TAFs.

Wood

MARINE

Issued 230 PM CST Sun Dec 21 2025

High pressure around 30.4 inches will move to the southeast tonight, as broad low pressure around 29.8 inches moves into the northern Great Plains. This will result in increasing southwest winds across the waters. Light snow should move into northern and central portions of the lake later tonight into Monday.

Winds will shift south and continue to increase Monday, as the low slowly moves east. Gusts to 30 knots are possible over southern Lake Michigan, with gales not expected at this time. A Small Craft Advisory may eventually be needed for the nearshore waters later Monday morning into Monday evening, mainly for building waves and some gusty winds.

Southwest winds will turn west later Monday night into Tuesday, as low pressure around 29.8 inches moves into Ontario. Winds will shift out of the northwest by Tuesday afternoon, as high pressure around 30.4 inches moves into the northern Great Plains. Winds will subside Tuesday night, as the high crosses Lake Michigan. These winds will shift out of the southeast Wednesday, as the high moves east of the region.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

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