textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A Winter Weather Advisory is in effect for Sauk County to Milwaukee County and southward into early Sunday morning. Widespread accumulating snowfall expected. Snow totals of 1 to 3 inches are expected north of Interstate 90 and 94, with 3 to 5 inches along and south of there. Localized totals around 6 inches are possible in far southwestern and far southeastern Wisconsin.

- Additional rounds of snowfall will be possible again Monday night into Tuesday and Tuesday night into Wednesday. Tuesday temperatures will likely rise above freezing, which means snow may start as rain.

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

- Below normal temperatures continue through next weekend.

UPDATE

Issued 954 PM CST Sat Dec 6 2025

No changes to the current Winter Weather Advisory headlines for now from Sauk to Milwaukee County and south overnight into early Sunday morning.

The light to moderate snow continues to steadily push east into the area, and should reach the lakeshore areas between 11 PM and midnight CST. This system continues to be driven by strong 850 mb frontogenesis response and the approaching 500 mb shortwave trough from the west. There is some warm air advection in the low levels also helping with the upward vertical motion. These features will move east through the area overnight and exit to the east early Sunday morning.

The snowfall rates should be around 1/2 inch per hour in southern portions of the area, with rates 3/4 to perhaps 1 inch per hour in the far south near the Illinois border, where the best frontogenesis response may occur.

Total snowfall amounts look to range from 2 to 5 inches in the advisory areas, with 1 to 2 inches to the north of there. There may be some lake enhancement in far southeast Wisconsin near the lake, which may bring some 6 inch amounts there. In addition, some 6 inch amounts may occur southwest of Madison, closest to the stronger 850 mb frontogenesis response.

There is some possibility for the 2 to 5 inch amounts to remain over the southern half of the area, so Sauk County may see a little less than forecast. For now, will leave them in the Advisory and see if the heavier bands remain to the south of there overnight.

The snow character is expected to remain rather fluffy, with snow to liquid ratios of 12 to 1 to 15 to 1 anticipated. The main impacts remain snow covered and slippery roads for overnight into early Sunday morning.

Wood

SHORT TERM

Issued 317 PM CST Sat Dec 6 2025

Tonight through Sunday night:

The clipper system tracking into southern Wisconsin tonight has taken shape across western Iowa and southwestern Minnesota this afternoon, with the strongest precipitation/frontogenesis area developing over central to northern Iowa. This lends credence to the southward shift of the mesoscale modeling that indicates the majority of QPF will fall across the southern two tiers of Wisconsin counties, but some individual models still indicate potential for a band of heavier precipitation in the Wisconsin River Valley, so for now will let Sauk County remain in the Winter Weather Advisory (currently covering Sauk County to Milwaukee County and all areas southward). Deep dendritic growth zones are noted in the soundings from the Wisconsin River Valley, so even with a shorter period of precipitation rates may reach near 1"/hr and create hazardous travel conditions.

These 1"/hr rates are also possible in banded precipitation near the WI/IL border, where precipitation also lasts longer, and in far southeastern Wisconsin where some lake enhancement is possible as winds turn northeasterly. Therefore, local accumulations up to 6 inches are possible along the border regions. Elsewhere within the Winter Weather Advisory, expect accumulations of 2 to 5 inches.

Precipitation will taper off into Sunday morning, with skies expected to clear through the day as arctic high pressure pushes in with northerly winds. Expect highs in the upper teens. Winds shift to northeasterly overnight Sunday, potentially bringing a diffuse band of lake effect snow slightly onshore. Not anticipating any strong banding or significant accumulations at this time (~20 percent chance of precipitation). Lows around zero degrees are expected across inland regions, with areas east of the Kettle Moraine slightly higher in the 5 to 15 degree range.

MH

LONG TERM

Issued 317 PM CST Sat Dec 6 2025

Monday through Saturday:

A lake effect snow band may brush southeast WI Monday morning before getting pushed into the north half of the lake by increasing southerly winds during the afternoon. High temperatures will reach the lower 20s and we can expect mostly cloudy skies.

A shortwave trough will track across WI during the day Monday, but the weak lift from vorticity and warm air advection (and dry low levels) should keep precip confined to central and northern WI during the afternoon.

A more robust shortwave trough will progress through central and northern WI Monday night into Tuesday morning. Broad low and mid level lift ahead of and along this wave will bring widespread, light snow to WI. Despite the likelihood of seeing snow (50-65% north of I-94 and 30-50% south), it only looks like around a half inch near Fond du Lac and Sheboygan, and trace amounts near the IL border.

Snow should exit by mid Tuesday morning. The next surface low in response to a stronger mid level shortwave trough will track from Saskatchewan to west central MN on Tuesday and across central WI Tuesday night. The 12Z runs of the ECMWF and GFS have come into better agreement on the track of the low, but there is still some uncertainty.

The big challenge with this Tuesday night event will be the precip type for southern WI. We will begin above freezing Tuesday afternoon in the warm sector and then likely remain in that warm sector if the low tracks across central WI. With loss of daylight, temps will probably sink just below freezing, but the temps aloft (925-850mb) should be in the 0-2C range south of the low. As long as we have deep enough saturation into the snow growth zone, then snow will be the primary ptype. But if we lose ice crystals, a wintry mix could occur. These are the details that will need to get hashed out as we get closer to the event.

Another arctic blast will move in behind that low. Gusty northwest winds are expected Wednesday afternoon, and lows will drop into the single digits for most areas Wednesday night. We could also see scattered light snow showers.

A swath of snow is expected to fall across the Midwest on Thursday. There are still big differences in the forecast location due to uncertainty in the amplification of the mid level shortwave trough. Some models clip far southern WI with the snow and others miss us all together. And... there is yet another chance for snow next weekend.

Cronce

AVIATION

Issued 954 PM CST Sat Dec 6 2025

The light to moderate snow continues to steadily push east into the area, and should reach the terminals near Lake Michigan between 05Z and 06Z Sunday. The snow will move east through the area overnight and exit to the east early Sunday morning.

The snowfall rates should be around 1/2 inch per hour for terminals in southern portions of the area, with rates 3/4 to perhaps 1 inch per hour for terminals near the Illinois border.

Total snowfall amounts look to range from 2 to 5 inches for the southern terminals, with 1 to 2 inches to the north. There may be some lake enhancement for Milwaukee and Kenosha, which may bring some 6 inch amounts there. In addition, some 6 inch amounts may occur southwest of Madison. The snow character is expected to remain rather fluffy.

Ceilings should drop to 1000 to 1500 feet AGL in southern portions of the area with the snow, with 1500 to 2000 feet AGL ceilings to the north. Visibility should drop to around 1 mile with the snow as well, with 3/4 to 1/2 mile values possible at times for terminals near the Illinois border.

Light northeast winds will become north overnight into Sunday morning, increasing Sunday afternoon and becoming gusty at times. Winds will become light again Sunday night, possibly shifting northeast for terminals near the lake.

There is a small chance for lake effect snow showers Sunday night for the lakeshore terminals, though confidence in this occurring is low at this time.

Wood

MARINE

Issued 954 PM CST Sat Dec 6 2025

Winds will increase and become north to northwest overnight into Sunday, as low pressure around 29.9 inches crosses central Illinois and Indiana. High pressure around 30.5 inches will also build into the Upper Midwest. A Small Craft Advisory is in effect for the nearshore waters south of Port Washington Sunday into early Monday morning.

Winds will shift to the south Monday afternoon, as low pressure around 30.0 inches passes north of Lake Superior. Another low around 29.7 inches will track from Minnesota to Sault Ste. Marie Monday night through Tuesday morning. A period of southerly gales up to 35 knots is looking more likely during this time for the open waters of Lake Michigan, with gusts up to 40 knots possible over far northern open waters.

The next low around 29.1 inches will track across central Wisconsin Tuesday night and reach southern Ontario by midday Wednesday. Gales are possible for the south half of the lake during this time.

A Small Craft Advisory will be needed for all of the nearshore waters Monday night through Wednesday night, with a few gale force gusts possible.

MRC/Wood

MKX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory...WIZ056-WIZ062-WIZ063-WIZ067-WIZ068- WIZ069 until 6 AM Sunday.

Winter Weather Advisory...WIZ064-WIZ065-WIZ066-WIZ070-WIZ071- WIZ072 until 8 AM Sunday.

LM...Small Craft Advisory...LMZ644...8 AM Sunday to 9 PM Sunday.

Small Craft Advisory...LMZ645-LMZ646...8 AM Sunday to 3 AM Monday.