textproduct: La Crosse

KEY MESSAGES

- Light snow slowly shifts south into northeast IA and southwest WI before exiting the local area by noon. Additional snow accumulations of a up to 0.5-1" expected.

- Additional snow moves into the region for Sunday morning and afternoon with accumulations of 0.5-1.5". Some blowing snow on Sunday evening cannot be ruled out west of the Mississippi River with increasing wind gusts.

- Well below normal temperatures from today and throughout next week with Monday being the coldest day. Winds chills on Sunday night and into Monday morning will likely (60-90% chance) be colder than 25 degrees below zero areawide. High temperatures on Monday will only rise into the single digits above and below zero.

DISCUSSION

Issued at 247 AM CST Sat Jan 17 2026

Today: Light Snow This Morning, Noticeably Colder and Blustery

An area of light snow continues to work through the area early this morning as SPC mesoanalysis depicts an area of 850mb frontogenesis center where this snowband is currently ongoing. Overall, visibilities within this band have generally been on the order of 1- 3 mile which accompanied with values of around 20dbz or less on reflectivity would suggest rates probably of around 0.25"/hr or less at most spots. As we continue to head through the morning, the 17.06z RAP generally shifts this axis of frontogenesis slowly to the south suggesting that snow will eventually move out of the local area by around the noon hour. Generally much of the CAMs agree on this, having the bulk of their reflectivity fields pushing south of the local area by around this time. As far as additional accumulations are concerned, given the light rates would only expect on the order of a few tenths to 0.5" with localized spots up to 1" on the high end just because of the higher snow to liquid ratios (NBM mean being around 20:1). Otherwise, will be noticeably cooler for today with highs generally in the single digits to teens areawide. Winds will remain blustery throughout much of the day as the surface pressure gradient remains fairly robust over the region. Consequently, expecting sustained winds in the 15-20 mph range with gusts up to 30 mph possible.

Sunday: Additional Accumulating Snow, Gusty Winds Behind Arctic Frontal Passage During the Evening

Sunday will continue to feature northwesterly upper-level flow across the local area. However, little modification to the current airmass will be present during the morning and afternoon hours as an additional shortwave will progress through the area. As this system works its way through, ensemble guidance and the CAMs generally agree on overspreading light snow throughout the local area. Overall the forcing associated with this wave is mostly mid-level QG convergence with the better 500-700mb frontogenesis in the 17.06z RAP diving south through central and northern IA where the CAMs have some slightly more invigorated snow showers. In any case, this wave will be fairly progressive, exiting the area during the early evening hours and with relatively limited moisture as PWATs in the NAM/RAP are unimpressive at only 0.1 to 0.2". As a result, accumulations in the HREF and NBM have probabilities for greater than 1" being fairly respectable (40-80% chance) north of the MN/IA state line. However, probabilities for over 2" are much lower (10-20%). What is a bit more impressive is the likely snow to liquid ratios with this that these probabilities were computed with. The recent long-range RAP soundings at La Crosse has as much as 350mb of dendritic growth zone residency which is very supportive of a lighter, more efficient accumulating snow. Consequently, the NBM mean snow to liquid ratio is around 20:1 for this system and based on model soundings this seems very reasonable. So while we are lacking in the moisture department in model guidance, if we do overachieve on moisture even slightly, snow accumulations could trend higher fairly easily.

As this system passes, an arctic front will swing through the area ushering in a much colder airmass into the evening and overnight. With this cold advection passing through, momentum transfer in the 17.00z NAM has 40 kt winds atop the mixed layer which could easily transfer down some 30-40 mph wind gusts Sunday evening and into the overnight. Cannot rule out this resulting in some patchy blowing snow (25% areal coverage) as the 17.00z HREF has medium probabilities (40-60%) west of the Mississippi River for visibility reductions of 1/2-mile or less due to new snow accumulation during the evening. Will be interesting to see if subsequent runs of the HREF maintain these probabilities.

Monday - Friday: Bitterly Cold Monday, Below Normal Temperatures Throughout the Upcoming Work Week

By Monday morning, deterministic guidance pushes the core of an arctic airmass into our south with 850mb temperatures falling to - 22C to -25C. Consequently, expecting temperatures for Monday morning to fall into the single digits below zero. Furthermore, with the ongoing blustery winds behind the frontal passage and tight surface pressure gradient with sustained winds of 15 to 25 mph likely still on Monday morning. Probabilities are high (60-90% chance) in the grand ensemble (GEFS/EC/Canadian ensemble) for wind chills to fall below -25F for much of the area. Additionally, high temperatures on Monday really will not improve much with values only in the single digits as suggested by the median of the NBM. This combined with blustery winds will mean afternoon wind chills will likely struggle to get above -10F, so really will not feel much better during the day.

As we progress through the week, temperatures "warm up" some into Tuesday as the colder core of 850mb temperatures exits, but likely will stay below normal with northwesterly flow reinforcing colder air into the region. As a result, the inter-quartile range for highs in the NBM throughout the upcoming work week remain in the single digits to low 20s. As far as snow chances are concerned, the next potential for this comes on Tuesday overnight and Wednesday morning. While deterministic guidance still varies on timing and intensity with this wave, the grand ensemble (GEFS/EC/Canadian ensemble) has been consistent with medium to high probabilities (40-70%) for measurable snow during this period. As a result, would expect the precipitation probabilities in the NBM to increase over the coming days.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1140 AM CST Sat Jan 17 2026

Light snow will continue into the mid afternoon as the snow gradually shifts southward across the area. MVFR CIGS through the afternoon before cloud bases increase above 3000ft for the evening and into the overnight. There is a 30 to 50% chance that MVFR CIGS remain through the overnight. Kept a scattered deck at 2500ft to indicate that MVFR CIGS overnight could be a possibility. MVFR to IFR CIGS return by mid morning Sunday as the next round of snow moves across the area. Breezy northwest winds today diminish this evening and gradually shift more southwest during the overnight. Strong northwest winds will move into the area Sunday afternoon and evening with sustained winds of 15 to 25 mph and gusts between 30 and 40 mph.

ARX WATCHES/WARNINGS/ADVISORIES

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