textproduct: La Crosse

KEY MESSAGES

- Accumulating snowfall is expected this afternoon, primarily over northeast Iowa where 1-2 inches is expected. Additional snowfall is possible (10-60%) Friday bringing a few tenths up to 1 inch of snow.

- Temperatures are on the decrease through the weekend, with highs on Saturday and Sunday in the single digits. Wind chills of -25F to -35F are expected Saturday and Sunday morning. A Cold Weather Advisory is in effect for portions of southeast Minnesota and west-central Wisconsin Saturday morning.

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

DISCUSSION

Issued at 158 PM CST Thu Dec 11 2025

Accumulating Snowfall this Afternoon and Friday

A winter system driven by a 700-500hPa shortwave trough ongoing across the central Great Plains will continue trudging southeastward this afternoon into the evening hours. A band of 800-600hPa frontogenesis is expected to drive snowfall and subsequent accumulations, but the southwest trend noted by the global ensemble and deterministic guidance has now been reflected within the high-resolution guidance, leading to high confidence in the majority of snowfall accumulations remaining southwest of our area. Accumulations around 1 inch are now expected for portions of northeast Iowa with a few tenths possible up to a line from Rochester, MN to Platteville, WI. Despite the continued decrease in snow amounts, expect some slippery travel during the evening commute where snow does accumulate.

Another shortwave moves into the region Friday morning, shifting eastward throughout the day. Positive vorticity advection, influence from the left exit region of an approaching jet streak, and weak 900-800hPa frontogenesis per the RAP associated with this wave should provide enough upward vertical motion to allow for snow development across the region. A subtle moisture tongue also shifts through the area along the wave, coinciding with a fairly deep DGZ depicted in RAP/HRRR soundings. This combined with the adequate forcing should provide some higher snow-liquid ratios, generally 15-20:1. On the backside of the primary wave, cold air advection should sufficiently steepen 0-1km lapse rates, generally 7-8C/km, which combined with lingering moisture should lead to some snow showers Friday afternoon into the evening, primarily along and north of I-94. Overall, probabilities are highest along and north of I-90 (30-60%) throughout the day, but some low potential exists across the whole region (10-30%).

Amounts on Friday look to be fairly light given the general lack of moisture and overall weak forcing, but with the aforementioned deep DGZ and higher expected snow-liquid ratios, accumulations should be on the order of a few tenths up to around 1 inch per the 11.12z HREF LPMM.

Cold Temperatures This Weekend

Strong high pressure sinks southeastward out of Canada through the weekend, ushering an Arctic airmass into the Upper Midwest. The first bout of cold air comes Friday night into Saturday, with wind chills falling into the double digits below zero, down to -30F for locations towards north-central Wisconsin. Have issued the season's first Cold Weather Advisory for Saturday morning for areas along and north of I-90 to highlight to dangerous cold. This may need to be extended southward, but given expected cloud cover, not as confident in the ultimate wind chill values further south.

Higher confidence in dangerous cold comes Saturday night into Sunday morning as the high pressure becomes more influential. Clearing skies overnight should allow for efficient radiational cooling, resulting in ambient temperatures falling into the teens below zero. Wind chill values fall to -25F to -35F during this period with the 11.00z LREF highlighting a 20-40% probability to fall below -35F west of the Mississippi River. These very cold temperatures will likely warrant additional cold weather headlines in the coming days.

Before the coldest air arrives Sunday morning, a band of 700hPa frontogenesis develops on the southern extent of the high pressure, sparking another ribbon of snowfall across portions of Minnesota and Iowa Saturday afternoon. This band of snow is currently expected to follow a very similar trajectory to today's snowband with a 20-50% probability of precipitation across northeast Iowa. With the similar trajectory, the greatest snowfall amounts are expected southwest of our area. Generally a few tenths of an inch of snow is expected as the 11.13z NBM highlights only a 10-20% probability for more than 1 inch.

Warmer and Drier Early Next Week

After the weekend, the upper level pattern finally begins to shift as longwave ridging builds into the central United States. This upper ridging is anticipated to bring a much needed reprieve from the active northwest flow of the past week or two, although there are a few shortwaves that traverse the mean flow through the beginning of the new week. However, with the ridge the dominant feature, these shortwaves tend to stay north of the local area along with any precipitation potential associated with them, so a few dry days are currently expected through at least the middle of the new week. Temperatures also being to warm with the rising heights and warm air advection under southwesterly low level flow, with the 11.13z NBM mean suggesting high temperatures will be far more seasonable, rising into the mid 30s through the beginning of the new week. By mid- week, ensemble guidance suggests the next winter system could move through our area, but far too much variability exists to glean much information apart from the possibility.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1115 PM CST Thu Dec 11 2025

CIGS: Mainly mvfr cigs return near/shortly after 12z Fri and will hang around through the afternoon. Expect them to exit east and give way to a bkn mid level vfr deck Fri 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 1-2sm 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 Friday night to 10 AM CST Saturday for WIZ017-029-032>034. MN...Cold Weather Advisory from midnight Friday night to 10 AM CST Saturday for MNZ079-086>088. IA...None.