textproduct: La Crosse

KEY MESSAGES

- Southern shift to tonight's storm system is verifying in upstream observations, so have adjusted warnings and advisories accordingly. Heaviest snow tonight will be near Highway 18 in Iowa.

- Below normal temperatures persist throughout the next week with Tuesday being the "warmest" day with highs rising into the 30s.

- Additional snow chances continue into next work week. Rain will likely mix in with snow late Tuesday for areas south of I-94.

UPDATE

Issued at 600 PM CST Sat Dec 6 2025

Upstream observations, radar imagery, and plow cameras in Minnesota are verifying what we had worried about earlier in the day...impacts on the north side of this winter system do not appear to be verifying. Light snow is occurring, but impacts to roadways looks to be minimal based on 511 page and traffic speed reports. Therefore, have cancelled the northern row of counties in the winter weather advisory along the I-90 corridor and trimmed Mitchell County, IA out of the warning. Also adjusted the end time of the hazards west of the Mississippi River given that snow will be ending around midnight.

DISCUSSION

Issued at 140 PM CST Sat Dec 6 2025

> WINTER STORM TONIGHT: taking a shift southward which would move the bulk of the local snowfall along/south of I-90.

HRRR/RAP morning runs coming in with a distinct shift southward with the winter storm track, more aligned with the very persistent, consistent GFS and EC, which never wavered much from this southern track. The HRRR remains even more aggressive with late morning/early afternoon runs - pushing the snow farther south. RAP has been more steady.

Ample lift in the projected snowband with sloping Fgen, isentropic upglide on the 280:295K sfcs, favorable low level QG convergence, and the parent shortwave itself. Some upper level jet support too.

DGZ mostly under 100 mb thick per RAP/HRRR soundings, but the SREF suggests a decent shot (over 30%) for 1"/hour rates within the heart of the band. EFIs are in the 0.7 to 0.8 range with a non-zero SoT in the band. Still confident that 6+" amounts will be reached in the band, less so in where that lays out.

With the CAMS aligning more with the global models...will shift the snowband a bit farther south. HREF/REFS still painting a 20-40% chance for 6+" of snow in the warning area of northeast IA across to far southwest WI. Amounts less around I-90, more 1 to 3" range now, but advisory still appropriate for this early season snowfall - and higher impact area (interstate travel). PLan to "stand pat" with current outlay of headlines for now. But, if the aggressive HRRR trend looks like reality, some adjustments to the headlines will be needed later this evening.

> NEXT WEEK: active pattern continues with periodic shots for precipitation. Still trending cold for the most part, but Tue still looking like a day many will warm above freezing.

Busy, progressive northwesterly flow a loft promises to spin a multitude of shortwave troughs across the upper Mississippi river valley. Some weak, some potentially strong.

On Mon/Mon night the GEFS and EPS continue to shift a couple weak perturbations across the region, one more south, one more north. THe northward shortwave looks a bit stronger and has a better chance to lay down minor accumulations of snow Mon night. Favored track has kept these chances across northern WI - and mostly away from the local forecast area.

The next shortwave should pack more of a "punch" as it drives across the northern plains Tue, spinning east/southeast across the region Tue night. While the GEFS and EPS have been in good agreement with relative strength and timing, positioning varies quite a bit - between and within the model suites. Some keep the related pcpn band across northern MN/WI. Others paint it across the local area. A few push it even farther south into northern IA. On the whole though, more favor a northern track.

There is surge of "milder" air ahead of the system which will complicate ptypes. GEFS and EPS have inched up expected highs for Tue over their last several runs with mid 30s now looking more likely (60 to 80% chance to warm above freezing). Of course, these temps reflect a more northward storm track. If it shifts south, so will the milder air. The low level warming looks like a rain or snow question at this time - not icy. Will let the model blend take the reigns for ptype for now. Where it does snow, plenty of forcing with deep QG convergence and sloping Fgen that a several inch band could be realized.

Colder air surges in post the Tue night system and should hold temps well below normal through the weekend. Other shortwaves will also bring more snow chances here and there.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 600 PM CST Sat Dec 6 2025

Widespread MVFR to IFR conditions due to snow are expected tonight, with the greatest impacts and best likelihood of temporary LIFR visibility restrictions (30-50% chance) along and south of an MCW to PVB line. Conditions improve to VFR from west to east after 06Z, with VFR conditions expected areawide after 12Z. Variable winds this evening become established from the NNW overnight at 5-10 kts and remain at this speed/heading through the day.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory until 6 AM CST Sunday for WIZ053>055- 061. MN...Winter Weather Advisory until 3 AM CST Sunday for MNZ094-095. Winter Weather Advisory until 6 AM CST Sunday for MNZ096. IA...Winter Weather Advisory until 3 AM CST Sunday for IAZ008>010. Winter Weather Advisory until 6 AM CST Sunday for IAZ011-030. Winter Storm Warning until 3 AM CST Sunday for IAZ018-019-029.