textproduct: La Crosse

KEY MESSAGES

- Two rounds of snow in quick succession tonight and again Wednesday afternoon.

- For tonight, a narrow band of 2-4 inches of snow is favored near the Highway 18 corridor while on Wednesday afternoon look for widespread snow amounts around 1". Increasing winds Wednesday afternoon and evening could result in blowing snow and reduced visibilities.

- Dangerously cold temperatures and wind chills settle across the region Thursday night and last into the weekend with morning wind chill values of -30 to -45.

DISCUSSION

Issued at 136 PM CST Tue Jan 20 2026

This Afternoon/Tonight: Narrow Band of Snow

A compact band of snow taking shape over South Dakota this afternoon is on target to skirt through the southern forecast area this evening and overnight. The heaviest snow amounts should fall in a narrow west-to-east corridor matching a band of lower tropospheric frontogenesis that intersects the near- surface DGZ. This relatively deep isothermal layer close to the DGZ coupled with this mesoscale forcing should result in a few hour period of higher snow rates in this band, though recent CAM runs have delayed the onset of saturation by an hour or two and cut into this accumulation window. Further north, the mid- level isentropic ascent ahead of the 700-500-mb wave will have to fight a deeper layer of sub-cloud dry air, but expectations is that we should precipitate at some point area-wide, with amounts taping off to less than an inch north of I-90 and a trace north of I-94. This snow departs between midnight and sunrise.

Wednesday Afternoon: Round 2 of Snow, Blowing Snow Possible

Fast on the heels of our overnight snow, a second PV lobe rotates southeastward around the quasi-stationary Hudson Bay low during the day on Wednesday. While there is some weak mesoscale frontogenesis attendant with the leading edge of the cold front Wednesday afternoon, the bulk of the snow will be generated within the corridor of enhanced synoptic kinematic lift. This forcing is transient in nature and the bulk of the snow will be in and out in a 6-hour window. However, stronger winds linger in the post-frontal airmass with some soundings showing winds at the top of the 850-mb mixed layer pushing 35 to 45 kts. These winds look strongest west of the Mississippi River and could result in localized visibility reductions of 1/2 of a mile or less. Will need to watch trends closely over the next 24 hours in case any headlines are needed for the blowing snow concerns.

Thursday Evening - Weekend: Dangerous Cold

Steady cold air advection ensues Wednesday night in the wake of our second round of snow. After reaching the mid-20s on Wednesday, highs struggle to reach the lower to mid teens for Thursday. A highly amplified mid to upper tropospheric West Coast ridge funnels Arctic air southward midweek, with this anomalously cold airmass arriving Thursday night ahead of a well-resolved 1055-mb high pressure cell sliding down the Canadian Rockies.

With the center of the high displaced well to the northwest Thursday night/Friday morning, the increasing pressure gradient coupled with plummeting temperatures will send wind chills tumbling overnight to between -30 and -45 by sunrise Friday. With a 6-mb spread in the pressure gradient across the forecast area by sunrise Friday, overnight temperatures should not stray too far from the forecast. If the boundary layer were to decouple (say at lower elevations/ sheltered areas), some of the 10th percentile solutions of the NBM distribution have lows falling to -20 to -30. However, such a scenario would not affect the forecast wind chills much given the needed reduction in wind speeds to achieve these lower temperatures.

Friday during the day remains cold as the 1048-mb high pressure cell approaches from the west with little opportunity for wind chills to improve above -25 to -30. With the high centered over the region Friday night, lows have the potential to crater to between -20 and -30, with a few outliers (5-10% probability) pushing -35 in favored locales in the Wisconsin sand bogs and central Wisconsin. Winds will be nearly calm during this time, so wind chills may actually be slightly higher than the previous night. However, even a slight wind could send wind chills back below -30 to -40.

The pattern begins to moderate by the end of the weekend into early next week as a Pacific airmass works eastward with highs back to near normal by Tuesday.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 532 PM CST Tue Jan 20 2026

There will be 2 rounds of snow that will be impacting the TAFs. The first round will move into the area this evening and then move out of the area before sunrise Wednesday. Snow totals at KLSE aand KRST will be up to 1 inch. Another round of snow will move in during the late morning and afternoon. Snow amounts will range from 1 to 2 inches at the TAF sites. Both rounds of snow will produce IFR/MVFR ceilings and visibilities.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Extreme Cold Watch from late Thursday night through Saturday morning for WIZ041>044-053>055-061. Winter Weather Advisory until 6 AM CST Wednesday for WIZ061. Extreme Cold Watch from Thursday evening through Saturday morning for WIZ017-029-032>034. MN...Extreme Cold Watch from late Thursday night through Saturday morning for MNZ096. Extreme Cold Watch from Thursday evening through Saturday morning for MNZ079-086>088-094-095. IA...Extreme Cold Watch from late Thursday night through Saturday morning for IAZ008>011-018-019-029-030. Winter Weather Advisory until 6 AM CST Wednesday for IAZ029- 030.