textproduct: Milwaukee/Sullivan

KEY MESSAGES

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

- A widespread light rainfall event is expected late Wednesday night through Thursday morning.

- Increasing concern for snow late Thursday afternoon into the evening with the front that may exhibit snow squall type behavior

- Significantly colder temperatures (overnight lows in the single digits to low teens) expected Thursday night, potentially flash freezing any surfaces that remain wet from Thursday's rain and snow.

SHORT TERM

Issued 300 PM CST Wed Dec 17 2025

Tonight through Thursday night:

High pressure will push out tonight as a fairly strong system slides in late tonight. The low pressure with this system will be around 985mb with strong southerly winds ahead of the initial front. Models have some initial precip potential ahead of the majority of the forcing primarily due to strong WAA, with the very strong LLJ in place, though the strongest forcing will remain in northern WI where the LLJ is upwards of 70-80 kts. However, as we get toward daybreak we will start to see significant forcing push in from the south and west. To the south we will likely see bands of light precip associated with the LLJ and associated WAA being directly overhead (though not as strong as in northern WI). This precip will be particularly maximized in northern IL but will likely leak into parts of southern WI where the omega shown in soundings really ramps up.

On the western side of the CWA, we expect to see significant overlapping forcing along the axis of the initial front. The surface front in combination with strong 850mb WAA, very strong PVA at 500mb, and strong Fgen throughout the column. This should lead to a period of decent rainfall Thursday morning across the CWA. This will however be fairly short-lived given how most of the forcing is co-located in a narrow area. It almost looks like just a band of precip in most of the CAMs.

Rain will likely push out by the late morning to the west and early afternoon to the east with dry conditions temporarily. However, we will then transition to the secondary front that will bring in the colder temperatures behind it. This will bring potentially significant impacts to southern WI. This front is looking increasingly more like a snow squall situation. The front, in combination with some instability and strong Fgen, looks likely to bring a band of snow, perhaps heavy, across at least parts of southern WI late Thursday afternoon during the evening commute. While there remains some uncertainty regarding what this may look like, how expansive it is and what the impact might be the concern has been heightened for this given the models showing a period where the snow squall parameter is on the higher side. We will continue to monitor this but rapid onset snow with potential for brief heavy snow, low visibilities and gusty winds would be possible. While these are short-lived the impacts can be significant for travel. In addition, following the frontal passage temperatures are expected to fall rapidly with lows in the single digits overnight. This will lead to concerns for flash freeze with any remnant water on roads likely freezing. This would make for potentially very slick road conditions into Friday morning.

Kuroski

LONG TERM

Issued 300 PM CST Wed Dec 17 2025

Friday through Thursday:

Friday will be chilly to start with potentially slick roads from overnight flash freeze potential but high pressure will move back in for Friday with no concerns for precip though temperatures will remain fairly chilly with highs in the 20s for the most part. Friday night through Saturday another system will push through but there remains uncertainty on what we may see, if anything, as models keep the system fairly dry given the absence of significant moisture. But if some moisture can be added to that system we could easily see some precip with it, likely a rain/snow mix with the current track and exactly where the 540 line lines up. High pressure then is expected to develop and strengthen later in the weekend.

Into early next week things become a bit more uncertain with a chance for precip Monday and again Wednesday night into Thursday. Ensembles show at least a 50% chance for 0.01 inches of precip for both days and thus it appears that various differences in tracks, moisture and intensity of these various system there is at least a decent chance for precip for these periods but likely heavily rely on the development of a few shortwaves in the upper levels that likely will not carry any significant precip with light rain or snow possible given the placement of the 540 line in models and corresponding surface temps.

Kuroski

AVIATION

Issued 300 PM CST Wed Dec 17 2025

FEW/SCT mid to upper level cloud deck will persist this afternoon. This deck will only remain for a bit with thick higher clouds pushing in this evening and another IFR/MVFR deck pushing in late this evening as the next system pushes in that will bring rain to southern WI through Thursday morning. There will be a period of moderate rain likely Thursday morning as the initial front sweeps across southern WI. CIGS may become LIFR at times with low CIGS generally lasting through the day though may intermittently clear up.

In addition, there is increasing concern for snow squall potential as the secondary front comes through late Thursday afternoon into the early evening with snow, breezy winds and likely decreased visibilities. Overnight expect flash freeze potential as rain on surfaces may freeze with rapidly declining temperatures overnight.

Kuroski

MARINE

Issued 300 PM CST Wed Dec 17 2025

Low pressure will track eastward along the Canadian border tonight into Thursday, bringing southerly gales from late evening through Thursday morning. A lull in the gales may occur Thursday afternoon as low pressure crosses the Upper Peninsula of Michigan. Winds become west and accelerate back to gale force behind a strong cold front Thursday evening, then eventually turn northwest Thursday night. A Gale Warning is in effect for all open waters of Lake Michigan late this evening through early Friday morning.

Westerly gales are expected in the nearshore areas from early Thursday evening through Friday morning.

Moderate freezing spray is expected to accompany the gales late Thursday night into Friday morning as a bitter cold airmass briefly enters our region.

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

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Gale Warning...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563- LMZ565-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...6 PM Wednesday to 6 PM Thursday.

Gale Warning...LMZ643-LMZ644-LMZ645-LMZ646...6 PM Thursday to 9 AM Friday.