textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Light snow chances (about 25 to 45 percent) are forecast 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.

UPDATE

Issued 955 AM CST Sun Dec 21 2025

Quiet weather is expected today, as high pressure slowly moves southeast of the region. Light winds will become southwest this afternoon, with highs in the 20s.

Warm air advection develops tonight into Monday, with an area of 850 mb to 700 mb frontogenesis response shifting east northeast through central and northern Wisconsin later tonight into Monday morning. This will bring a period of light snow to northern and central Wisconsin, with the northern portions of the area on the southern edge of any light snow. The GFS has been consistent with bringing measurable QPF/light snow amounts to the far northern and northeastern parts of the area during this period, with the NAM north of the area and the ECMWF between them but with lighter QPF.

Ensemble guidance continues to focus mostly north of the area with any measurable QPF/light snow. CAMs have some reflectivity moving through, but most of the measurable QPF remains to the north as well. Forecast soundings from northern parts of the area are showing a dry layer of air below 850 mb through this period. This will be the negating factor for measurable QPF/light snow in northern parts of the area.

For now, the 25 to 45 percent PoPs seem reasonable in the northern parts of the area, with a dry forecast toward the far southern areas. At this time, it appears that most impacts will be north of the area later tonight into Monday morning. Once the full 12Z suite of model guidance comes in, will assess the need for any changes.

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 light drizzle to occur 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. Will assess these trends as well with the 12Z suite of model guidance.

Wood

SHORT TERM

Issued 342 AM CST Sun Dec 21 2025

Today through Monday:

Synopsis/Mesoanalysis: High pressure is moving into southern Wisconsin this morning, with northwest winds starting to taper in western locations. Weakening trends will continue areawide through daybreak as the aforementioned surface high continues to build into the region. The high will drift east of the area this afternoon, resulting in a southwest wind shift by early evening. South to southwest winds will continue through the day on Monday. Evident in 00Z upper air analyses, an upper jet streak is currently situated over the northern Rocky Mountains, and is forecast to build into the Upper Mississippi River Valley tonight. Responding to the encroaching jet streak, broad low level warm advection will thus increase across the western Great Lakes tonight. A combination of upper divergence within the jet & isentropic ascent within the warm advection belt will support increasing precipitation chances from the late overnight into Monday morning, particularly to the north of I-94 and US-18. Precip will begin as light snow, with some light drizzle, freezing drizzle or sleet pellets possibly mixing in as precipitation tapers early Monday afternoon. Accumulations & impacts are expected to remain minimal.

Tonight through Monday Morning: Precip chances (~25-45%) will gradually trend upward after midnight to the north of I-94/US-18 as upper divergence & isentropic ascent increase regionally. The steadiest precipitation is likely to focus along a band of frontogenesis in the 850-700 mb layer, which is initially forecast to materialize over northern zones prior to translating northeast later Monday morning. Thus anticipate a north-south cutoff in precip given a quick drop off in lift affiliated with the frontogenesis. Precip will begin as all snow, though some freezing drizzle or sleet could mix in later Monday morning as the deepest frontogenesis moves north & cloud ice wanes. Probabilistic snow forecasts are pessimistic regarding accumulation potential, which seems reasonable given the anticipated movement of the frontogenesis band to the northeast of the area. Could nevertheless see a light dusting of snow across our northern tier of counties, where guidance does indicate some (~10-20%) potential for 0.1". Very minor (if any) impacts are thus anticipated in precipitation.

Monday Afternoon: Wintry precip is largely expected to pass north & east of the region. With broad lift still in place across the region, will need to monitor for some small (~10-15%) potential for drizzle or very light rain/snow mix. Don't expect any accumulations or impacts in the event light precip hangs on into the afternoon hours.

Quigley

LONG TERM

Issued 342 AM CST Sun Dec 21 2025

Monday night through Saturday:

A building ridge across much of the United States will bring warming temperatures to the region for mid week. Highs will warm into the upper 30s and low 40s for Tuesday, with low 40s expected for all but central Wisconsin on Wednesday. Christmas Day continues to look like the warmest day of the week, with mid to upper 40s looking probable, and a few low 50s not out of the question near the state line.

Tuesday and Wednesday look dry, with increasing moisture Wednesday night and Thursday perhaps leading to some light rain showers or drizzle Christmas Eve and Christmas Day, as a weak shortwave rides the northern periphery of the ridge. High pressure builds in behind that feature for Friday, favoring dry and somewhat cooler conditions.

Boxell

AVIATION

Issued 955 AM CST Sun Dec 21 2025

Quiet weather is expected today, as high pressure slowly moves southeast of the region. Light winds will become southwest this afternoon, then south tonight into Monday. 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 3500 feet AGL toward Sheboygan and may lower at all locations to perhaps 2500 feet AGL 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, so may keep a PROB30 mention in their TAF for now for that period. There may be some light drizzle Monday afternoon and evening, with perhaps some light freezing drizzle in the evening, if surface temperatures drop to the freezing mark. For now, will leave this mention out of the TAFs.

Wood

MARINE

Issued 955 AM CST Sun Dec 21 2025

High pressure around 30.4 inches will pass just south the open waters today, resulting in continued decreasing winds. The high will progress east tonight, as broad low pressure around 29.8 inches moves into the northern Great Plains. This will result in a southwest wind shift across the waters. Areas of rain and snow showers are possible tonight.

Winds will shift south and increase further during the day on Monday, as the aforementioned low slowly moves east. Gusts of 25 to 30 knots are possible over southern Lake Michigan, with gales not expected at this time. A Small Craft Advisory may be needed for the nearshore waters Monday into Monday night, for the gusty winds and building waves.

Winds will turn westerly Monday night into Tuesday, as low pressure moves into Ontario. Winds will shift out of the northwest Tuesday, as high pressure around 30.2 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.

Quigley/Wood

MKX WATCHES/WARNINGS/ADVISORIES

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