textproduct: La Crosse

KEY MESSAGES

- Risk for a glaze of ice along I-94 to upwards of 0.10" of ice north of Highway 29 continues to increase (60-80%) and have issued a winter weather advisory to cover this hazard.

- Fog erodes from north to south early this morning, but could build back northward today and tonight.

- Highs run 10-15 degrees above average through Saturday, with falling temperatures on Sunday behind a cold front and temperatures 20-30 degrees colder by Monday morning.

- Strong winds and light snow accompany the passage of the cold front on Sunday, which could negatively impact travel.

DISCUSSION

Issued at 350 AM CST Thu Dec 25 2025

Today: Cloudy with Drizzle Spreading North

Widespread fog developed overnight in the wake of last night's drizzle, but drier northerly flow has been steadily eroding the fog and low stratus through the night and as of 4 am the bulk of the dense fog had been relegated to areas along and west of Highway 63. However, with the near-surface flow veering back to the southeast by this afternoon with the passage of a 700-500-mb ridge axis and increasing 290K isentropic ascent ahead of the next warm front, the low clouds and fog spread back northward through the afternoon. This increasing upglide should aid in the development of drizzle that spreads northward with this stratus, though with the depth of the boundary layer moisture flirting with the 1-km threshold we generally see for drizzle production, kept PoPs on the lower side through sunset.

Tonight - Friday Morning: Icing Risk Along and North of I-94

Temperatures across central Wisconsin have fallen into the low to mid-20s early this morning and will struggle to reach 30 degrees today given the increasing clouds and easterly flow. By the time the aforementioned drizzle arrives this evening, the below freezing temperatures will result in icing conditions on untreated surfaces. The greatest risk for travel impacts looks to be along and north of Highway 10 with icing amounts approaching 0.10" north of Highway 29 were the moisture profiles are deeper.

However, did include the I-94 corridor in the advisory given that wet bulbs will be below freezing through at least midnight and present a window for a light glaze of ice to form. The forecast along I-94 is quite sensitive to small changes in the temperature/dewpoint that should be monitored through the day. With increasing theta-e advection through the night, surface temperatures begin to warm after midnight and the risk for freezing precipitation should end before mid-morning in central Wisconsin.

Friday - Saturday: Drier and Warm

With the overall pattern amplifying in the wake of tonight's system and the flow turning more to the southwest, tomorrow and Saturday feature our warmest temperatures of the period with many locales cracking the 40-45 degree mark. Roughly 20-30% of the NBM ensemble members have areas south of Highway 18 closing in on 50 degrees tomorrow, spreading as far north as I-90 for Saturday. Saturday night's lows look to only fall into the mid to upper 30s.

Sunday: Cold Front Arrives

Those 30 degree readings at sunrise on Sunday will be the warmest we see through at least the first half of the new week. The timing of the cold front has been sliding later in time by about 6-12 hours later over the last few days, but it doesn't change the forecast much for Sunday with falling temperatures through the day.

With the forecast low track and resultant deformation zone sliding southward and more into the forecast area, the risk for accumulating snow with its passage is on the increase. Amounts don't look to be too high at this time given the progressive nature of the system, but 10-20% of the NBM ensemble members have snow amounts in excess of 2" and a few outliers exceed 4".

Strong winds will accompany the post-frontal airmass with at least 60-70% of the NBM membership showing wind gusts of 35-45 mph. Combined with the light/blowable snow and falling temperatures, we will need to monitor trends for travel impacts as we get closer to this event.

Monday - Wednesday: Cool Start to the Week, Drier

The colder air floods south for Sunday night with lows in the single digits and wind chills in the teens below zero Monday morning. Highs look to stay below 20 for the day on Monday as a transient surface ridge slides through.

Moderating temperatures do arrive by Tuesday and Wednesday as highs return closer to average. To what extent temperatures rebound is somewhat uncertain given how the region will reside along the downstream flank of a sharper ridge that could funnel colder air into the region. In fact, the NBM has a nearly 30 degree spread in the high temperature forecast by midweek, indicative of how we will reside along the transition zone between two airmasses. There are a few token shots of snow that could move through, but nothing to hang ones at on at this range in the forecast.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1145 AM CST Thu Dec 25 2025

A shortwave trough will move east across the area tonight and Friday. Warm air advection ahead of this wave will result in fog (likely dense west of the Mississippi River) and areas of drizzle across the area tonight and Friday morning. Ceilings and visibilities will range from LIFR to MVFR through of the TAF period.

For areas along and north of Interstate 94, there will be some freezing drizzle from tonight into Friday morning.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory from 6 PM this evening to 9 AM CST Friday for WIZ017-029. Winter Weather Advisory from 6 PM this evening to 6 AM CST Friday for WIZ033-034-042>044. MN...None. IA...None.