textproduct: La Crosse

KEY MESSAGES

- Light snow is likely (70-90%) this morning into the early afternoon hours, primarily south of I-94. Accumulations around 0.5-1 inch are expected.

- Cold air moves in tonight, resulting in a cold start to the new year. Wind chills 10 to 20 degrees below zero are expected tonight into the morning of New Year's Day. High temperatures top out in the teens New Year's Day.

- Drier conditions and near to slightly above normal temperatures are expected for the beginning of the new year.

UPDATE

Issued at 730 AM CST Wed Dec 31 2025

Quick update to add some patchy drizzle or freezing drizzle near and south of I-90 for a few hours this morning. Have also bounced precipitation chances into the 90-100% chance range as snow makes its way into the area from the northwest. Radar and observations indicate areas north of I-94 are snowing or will begin shortly in northcentral WI. Short term forecast model guidance isnt handling the northern snow area well. Secondary band is now intensifying to the northwest in a 600-700 mb frontogenetic forcing region, just west of the Twin Cities and will quickly spread into the area from 9am to noon with what could be snow, rain, or a mix of both to start as cold air is slow to arrive. The mix should mainly be south of I-94 this morning. The main precipitation band, which will last much of the day, should align from MSP-LSE-MSN.

Colder temperatures (and the front) will arrive from north to south today and undercut the precipitation band...converting all types to snow. Have slowed this arrival slightly with the front roughly located along a Wausau-MSP-Aberdeen line at 13Z.

DISCUSSION

Issued at 356 AM CST Wed Dec 31 2025

Light Snow Today

A cold front, currently situated over northern Minnesota, will sink southward into the Upper Mississippi River Valley this morning supported by upper level troughing located over the Great Lakes region. Low level forcing along the front combined with 0-1km lapse rates steepening to 6-7 C/km in the cold air advection, and 700-800hPa frontogenesis are expected to provide enough upward vertical motion within a saturating atmosphere to support southeastward moving light snowfall into the afternoon (70-90%). There is some uncertainty in where the axis of highest snowfall will ultimately set-up given slight latitudinal variations among the high resolution guidance, but the majority of the 30.12z LREF membership (60-80%) highlights areas generally along a line from the Twin Cities to southwest Wisconsin as the most favorable to see snowfall today.

Snowfall amounts will be light as the 31.00z HREF LPMM depicts 24 hour QPF around 0.05 inches across our area, equating to accumulations of around 0.5"-1" when adjusted for expected snow-liquid ratios of 12-18:1. Can't completely rule out some flurries in the wake of the primary snowfall given the steepened low level lapse rates, although saturation will be shallow at best, limiting confidence to 10-30%.

Cold Temperatures Tonight into New Year's Day

Falling temperatures are expected overnight into the morning of New Year's Day as cold air advances into the region under northwesterly flow. Drier air also moves into the region, which should lead to at least a few hours of clearing skies overnight, allowing for a period of efficient radiational cooling. As such, have trended temperatures towards the 25th percentile of the 31.01z NBM but if skies clear earlier than expected, temperatures may fall further than currently forecast.

As it stands now, temperatures are expected to be in the single digits above and below zero to ring in the new year, coldest over central to north-central Wisconsin. Given the cold temperatures, wind chills of 10 to 20 degrees below zero are possible, so ensure you're dressed appropriately if venturing outside for New Year's Eve celebrations tonight.

Drier and Near to Slightly Above Normal Temperatures

Longwave ridging builds into the United States over the next several days, resulting in overall drier conditions and warming temperatures across the Upper Midwest. There remains the low potential (10-30%) of some light snow along and north of I-94 during the afternoon and evening of New Year's Day associated with a weak ripple in the northwest flow aloft, but as the ridge becomes more dominant over the course of the coming days, impactful weather becomes less probable with near to slightly above normal temperatures expected.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1133 AM CST Wed Dec 31 2025

Trend: Removed KRST from IFR visibilities in snow today. There could be brief IFR periods this afternoon still, but it should mainly be MVFR. Added some RA at KLSE with 36F being reported.

Challenging forecast with a cold front moving through in the next several hours, persistant but weaker lift in a band of precipitation suggesting snow, but warm air in place at the surface across much of the area from Interstate 90 south promoting rain. Challenging to judge how far visibilities will go down in the snow, once it changes over with the cold front moving through. Eventually, all sites will convert to snow, but likely a period here this afternoon of -RA before that occurs...on I-90 and south. The band has been persistent over KMSP this morning and has struggled to make it southeast. The lift should translate southeast over the area and provide a lower MVFR or upper IFR snow /2-3SM/ through late afternoon before shifting southeast of the area completely.

Have added another snow chance late in the TAF period as confidence is increasing that there will be another light snow period Thursday late morning and early afternoon across the area. Very similar to today. Saturation is a struggle the further south and west from La Crosse for SN to be observed. If you are flying NY day, monitor forecast trends.

ARX WATCHES/WARNINGS/ADVISORIES

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