textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Milder temperatures expected through early Thursday, with highs in the middle to upper 30s.

- 65-90% rain chances are forecast from late Wednesday night through Thursday morning. There are 20-40% chances for light precipitation to continue Thursday afternoon and evening, with a gradual transition to light snow.

- Significantly colder temperatures (single digit low temps) expected Thursday night, freezing any surfaces that remain wet from Thursday's rain and snow.

SHORT TERM

Issued 338 PM CST Tue Dec 16 2025

Tonight through Wednesday night:

A surface trough/cold front will slide across southern WI tonight. This is coincident with a mid level trough. South- southwest winds are gusty ahead of it and northwest winds will continue to be a little gusty behind it during the overnight hours. Our temperatures over-performed this afternoon with the extreme warm air advection. Expect mid level clouds along the front this evening. There is a chance for some scattered low clouds behind it during the overnight hours due to trapped low level moisture, but the air (and winds) just above the inversion will be very dry (and gusty). The question is how much mixing will occur down to the surface behind the front. The hinting of low clouds from the models and trapped low level moisture may also be from the melting snow with the mild temps this afternoon. The winds should be high enough to prevent fog, but the stratus would be the result instead.

Wednesday, the surface high will slide across IL, so winds over southern WI will actually be light and generally out of the west. If clouds stall over the IL/WI border along the weakening front Wed morning, this will slow down our cooling tonight but also the warming on Wednesday. However, low pressure approaching from the Northern Plains will bring us right back into a warming pattern by Wed afternoon. With sunshine and increasing southerly winds, we should be able to get back into at least the mid 30s, but given how this afternoon over- performed, I would not be surprised to see 40 along the IL border. Fog is possible Wednesday night.

Cronce

LONG TERM

Issued 338 PM CST Tue Dec 16 2025

Thursday through Tuesday:

Low level moisture will surge into southern WI early Thursday morning. Rain or drizzle is possible initially (30 to 50% chance), and then deeper moisture will arrive shortly after 12Z/6AM as the surface low of this occluding system tracks into northeast MN. The initial surface trough/cold front will slide through southern WI during the daylight hours, and the secondary cold front (925-850mb cold front) will cross during the late afternoon/evening hours. This secondary front will feature gusty west to northwest winds and a sudden drop in temperatures. Thu nt lows will drop into the single digits to lower teens, with min apparent temps in the negative single digits.

A high pressure ridge will return Friday afternoon with lighter winds and highs in the lower to mid 20s. The next clipper will cross Ontario near Lake Superior Saturday. Southern WI will be above freezing in most of southern WI during the day, with the precip chances mainly over northern WI. One more weaker clipper will take the same track Sunday evening and should not impact us.

Monday afternoon and evening could bring a wintry mix to southern WI with a period of warm air advection as the next clipper approaches. This could lay out a stalled frontal boundary over southern WI on Tuesday, so a period of light rain or at least low clouds is possible.

Cronce

AVIATION

Issued 338 PM CST Tue Dec 16 2025

Dry weather and VFR continue through this evening, with some mid to high clouds and gusty southerly winds ahead of an approaching low pressure trough/cold front. Forecast models continue to hint at some potential for a period of MVFR altitude clouds behind this front during the overnight hours. This would be to low level moisture (from melting snow) trapped beneath an inversion. Expecting just enough wind to prevent fog, so this moisture could become stratus. Just above the inversion, the air will be very dry and feature strong northwest winds. The amount of mixing behind the front during the overnight hours is uncertain. We have LLWS mentioned in TAFs and FEW020 as a hint to cover the possibility.

Cronce

MARINE

Issued 338 PM CST Tue Dec 16 2025

High pressure will linger across the Southeast U.S. through Wednesday. Meanwhile, low pressure currently over southwestern Ontario will lift into western Quebec tonight, leading to continued gales across the northern two-thirds of the open waters through early Wednesday morning. A Gale Warning is in effect. Winds will veer westerly then northwesterly and diminish into early Wednesday morning behind a cold front. Light winds then are expected through Wednesday afternoon. The Small Craft Advisory is in effect through late tonight.

Low pressure then tracks eastward along the Canadian border Wednesday night into Thursday, bringing southerly gales once again late Wednesday night into Thursday morning. A brief period of lighter winds is expected Thursday morning into Thursday afternoon as low pressure crosses the Upper Peninsula of Michigan. Winds turn westerly, then northwesterly Thursday evening, with gales returning to the southern half of the open waters early Thursday evening. Northwesterly gales will return to the northern half late Thursday night. Gale Watches are in effect for each area for these time frames. Winds will diminish below gale force Friday morning and become light and variable.

Friday night, another low pressure system swings through southern Canada, bringing gusty south-southwest winds once again. Gales are possible, but confidence is lower with timing and intensity at this time.

Cronce/MH

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ669-LMZ671-LMZ673-LMZ868-LMZ870-LMZ872-LMZ874 until 3 AM Wednesday.

Gale Watch...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565...11 PM Wednesday to 10 AM Thursday.

Gale Watch...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777- LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...11 PM Wednesday to 9 AM Friday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 6 AM Wednesday.