textproduct: La Crosse

KEY MESSAGES

- A wintry mix of snow and very light freezing rain is looking more probable along and north of Interstate 90 tonight from 12-6 am. A light glaze of ice is possible with the highest probabilities targeting a line from Wabasha- Jackson county (50-60%) - lowering south to I-90. Mainly snow is expected north of I-94, lasting into mid-Monday morning, where totals will be up to 1 inch.

- Above normal temperatures for much of this week with highs generally in the 30s and 40s.

DISCUSSION

Issued at 139 PM CST Sun Dec 21 2025

Today-Monday: Dry Today, Mixed Precipitation Possible Tonight into Monday Morning

Surface high remains over the area today keeping skies mostly clear with the subsidence in the low levels. After a chilly start to the day, highs increase back in the mid to upper 30s for most. By this evening, zonal upper level flow takes over and a shortwave dips down into the north central Plains. A weak warm front shifts northward into our area and with it, a little bit of moisture advection. This wave increases precipitation chances mostly along and north of I-90. Dewpoints increase from the teens into the low to mid 20s as the front approaches. Along this boundary, there will be quite a bit of lift in the low levels. One key note about the precipitation chances overnight is that the low levels, roughly between 1000 and 3000ft, will be quite dry. The question then becomes, does the amount of potential lift overcome the dry air. As southwest winds between 850mb and 950mb increase into the 35 to 45kt range, strong warm air advection infiltrates this layer, giving way to temperatures between 2 and 5C. With surface temperatures right below freezing and the strong warm nose as observed in the forecasted soundings for these locations, if precipitation can make it to the surface, it would more than likely be liquid as there would not be enough resonance time to refreeze the droplets. Last week near the Twin Cities, soundings at 12Z on Tuesday, were pretty similar to our forecasted soundings and that resulted in rain droplets breaking through the dry layer and reaching the surface resulting in a quick glaze of ice. Another thing to note is that compared to previous forecasts, there has been a slight uptick in precipitation amounts. With this increase in amounts, have adjusted precipitation chances to better match up. The area that would see the best chance of freezing rain would be roughly between I-90 and I-94. Locations north of I-94 will likely stay cool enough as the warm air advection is not as strong up there and the resulting precipitation type would stay all snow. Snow amounts of 0.5 to 1" are expected north of I-90 with parts of Taylor County potentially getting up to 1.5". For areas between I-90 and I-94, a glaze of ice up to a couple hundredths will be possible, with the highest amounts in Wabasha, Buffalo, Trempealeau, and Jackson counties.

Tuesday-Sunday: Warmer Than Normal Temperatures, Mostly Dry

The zonal flow shifts to a more southwest flow, increasing and maintaining the warm air advection through much of the central CONUS. While there are a few cold fronts that pass through, southwest winds come back to help increase temperatures during the day. Ensemble and deterministic guidance continues to favor a ridge pushing into the central CONUS on Tuesday and staying through much of the week. The main difference with these ensembles is how amplified the ridge can get as this will impact temperatures the most. There are some instances where a wave sneaks in under the ridge such as Wednesday night into Christmas and again Christmas Day into Friday. Both waves increase precipitation chances, but there is uncertainty on where these chances are at. The GEFS doesn't really support this while much of the EPS members have measurable precipitation for much of the CWA. Heading into Christmas Day, a low develops out of the Central Rockies and moves northeast towards the Upper Midwest. Not much is expected precipitation wise with this system until later Christmas night and into Friday. Depending on where this low tracks will also help to determine how cool or warm the CWA gets. Current forecasted highs are generally in the 30s to low 40s for most days with Christmas Day being the warmest. High temperatures for Christmas are in the upper 30s to mid 40s. When looking at LREF cluster probabilities for temperatures for Christmas Day, There still remains a 40% chance that the ridge is more amplified and results in higher probabilities (30 to 60%) for temperatures greater than 45F for areas along and south of I-90.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1125 AM CST Sun Dec 21 2025

VFR conditions are expected but LLWS and chances for FZRA do accompany those conditions.

LLWS...Overnight the low-level wind field increases off the surface to about 2kft to cause a period of LLWS across much of the area. The wind shear is 32-35 kts within that layer based on little mechanical mixing and a strong inversion in place.

A period of FZRA/SN will traverse the area from southwest to northeast increasing in intensity as it shifts northeast. With warm temperatures aloft and below freezing near at the surface, some freezing rain is possible north of I-90 in the 06-12Z window. Some ice pellets or snow may also mix in. A light glaze of ice is possible by sunrise Monday - with probabilities increasing north of I-90 (40-70% KRGK-KBCK). Have included a PROB30 for that wintry mix for the KRST/KLSE TAFs which are located on the southern edge of the probabilities. Snow is expected north of I-94.

ARX WATCHES/WARNINGS/ADVISORIES

WI...None. MN...None. IA...None.