textproduct: La Crosse

KEY MESSAGES

- Light snow this morning and afternoon. Accumulations primarily less than 0.5". Light snow for northeast Iowa Saturday morning with minimal accumulations expected.

- Bitter cold this weekend, with highs on Saturday and Sunday in the single digits. Wind chills of -15F to -35F are expected Saturday and Sunday morning. A Cold Weather Advisory is in effect for southeast Minnesota and western Wisconsin Saturday morning through Sunday morning.

- Trending towards more seasonable temperatures and drier conditions for early next week with high temperatures rebounding into the mid 30s.

DISCUSSION

Issued at 336 AM CST Fri Dec 12 2025

Today: Light Snow

An upper level low over southern Manitoba and western Ontario will move east during the day as it is apart of the larger longwave trough that is situated over the Upper Midwest to New England area. With the local area in the left exit region of an approaching jet streak and a brief period of positive vorticity advection during the afternoon, enough lift will be present for some light snow to develop across much of the forecast area. The RAP shows a slight increase in moisture advection over the region later this morning and through the afternoon to also aid in snow development. Snow ratios will stay on the higher side, 17 to 20:1. The snow will be around for a short time, around 6 to 8 hours. Minor accumulation of up to 0.5" will be possible, with the best chance at seeing 0.5" up in north central Wisconsin.

The Weekend: Bitter Cold Temperatures

That same upper level low shifts over the northern Great Lakes as cold air advection begins to move into the area on the back side of the low, temperatures will get colder. This in face will be our coldest temperatures of the season so far. It begins Friday night into Saturday morning where wind chills of -20 to -30 will be possible and as result we have a Cold Weather Advisory in place for southeast Minnesota and western Wisconsin where wind chills of at least -20 degrees are expected. Not much relief for Saturday afternoon and into the evening where wind chills remain in the -10 to -20 range. Higher confidence in even colder temperatures for Saturday night into Sunday morning where an EFI value -0.8 to -0.95 exists over our forecast area. These values indicate that forecasted temperatures for Saturday night/Sunday morning are on the lower side of climatological normal for this time of year. Another important thing to note is that on Saturday we are under cloudy skies and begin to clear out by the evening. Mostly clear skies are expected during the overnight and through Sunday morning helping to lower temperatures even more due to radiational cooling. Forecasted low temperatures are between -10 and -17 degrees with wind chills of -25 to -35 degrees expected for most locations. The only difference is how long a location will be below -25 degrees for the wind chill. Locations in far southwestern Wisconsin and portions of northeast Iowa will see these wind chills after midnight Sunday morning. There even is a low probability (30 to 50%), based on the 12Z LREF, of wind chills getting colder than -35 degrees in portions of southeast Minnesota and northeast Iowa. With these cold wind chills, another cold weather headline will be needed in the next day or two.

In addition to the cold temperatures, shortwave energy comes down from the upper level low situated over the northern Great Lakes and in doing so, a band of 700mb frontogenesis develops and moves over northeast Iowa Saturday morning into the afternoon. The track of this frontogenesis band is very similar to the previous snow band that fell across northern and eastern Iowa on Thursday. While some flurries may be possible as far north as I-90, the northern portion of the band looks to impact areas south of a Mason City, IA to Guttenberg, IA line. Most locations from I-90 south to this line will see flurries to maybe a couple tenths of snow, while south of the Mason City to Guttenberg line could see around 0.5 to 1" of snow. NBM probabilities for at least 1" of snow are between 20 and 40% with the highest percentages in the southern portions of Floyd, Chickasaw, Fayette, and Clayton counties.

Monday-Wednesday: Warmer and Drier

As the back side of the longwave trough continues its trek eastward, upper level ridging finally breaks through and covers the Upper Midwest for early next week. With southwest winds, good warm air advection will be in place and help to increase temperatures into the low to mid 30s for Tuesday and the mid 30s to potentially 40 degrees for some locations! The most recent NBM gives a probability for at least 40 degrees of 30 to 50% for portions of southwest Wisconsin and northeast Iowa, especially river valleys in these areas. While under the ridge, shortwave will pass to our north and leave our local area dry for the first part of next week. This will be a nice break from the active pattern that we have seen over the past couple of weeks. Once Thursday roles around, the ridge breaks down and the flow becomes zonal or slightly northwest, which translates to a potential flip back to an active pattern for the second half of next week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 500 AM CST Thu Dec 11 2025

CIGS: Mainly mvfr cigs return shortly after 12z and will hang around through the afternoon. Expect them to exit east and give way to a bkn mid level vfr deck this evening.

WX/vsby: upper level trough/sfc cold front will produce areas of -sn with the potential for a few shsn that could drop vsbys briefly into the 2sm range. This activity will exit east by early afternoon. Minimal if any accumulation expected.

WINDS: light winds become southwest then increase and go more west/northwest with the passage of that cold front by late morning/early afternoon. The winds look to stay "up" Friday night through Sat as the pressure gradient doesn't start to slacken until later Sat night with the approach of high pressure.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Cold Weather Advisory from midnight tonight to 10 AM CST Sunday for WIZ017-029-032>034-041>044-053. MN...Cold Weather Advisory from midnight tonight to 10 AM CST Sunday for MNZ079-086>088-094>096. IA...None.