textproduct: La Crosse

KEY MESSAGES

- Some shift southward of the winter storm track, with subsequent shift south of the heavier snow band. Amounts trending a bit less than previous forecasts, and mostly from along and south of I-90. Highest amounts locally still look to fall across parts of northeast IA into far southwest WI (3 to 6", 20-40% chance to exceed 6"). Advisories/Warnings continue, but if southward shift of band continues, expect some revisions as the evening wears on.

- 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.

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 /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1131 AM CST Sat Dec 6 2025

Incoming snow seen on radar imagery traversing the Missouri River Valley from eastern South Dakota through western Iowa early this afternoon. Accompanying impacts likely drop into IFR visibilities per local climatology. IFR to MVFR ceilings linger post snowfall overnight with low level cold air advection saturating the lowest levels.

Drier air within this colder airmass suggests VFR potential Sunday morning as cold air advection weakens. Low confidence situation given model bias to remove impacts at longer forecast hour as well as select model biases in sustaining low level saturation.

Subsequent aviation impacts frequent the longer term forecast: accompanying small show chances Sunday night through Monday morning and again Monday through Thursday.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory from 6 PM this evening to 6 AM CST Sunday for WIZ041>043-053>055-061. MN...Winter Weather Advisory until 6 AM CST Sunday for MNZ086-087- 094-095. Winter Weather Advisory from 6 PM this evening to 6 AM CST Sunday for MNZ088-096. IA...Winter Storm Warning until 6 AM CST Sunday for IAZ008-018-019- 029. Winter Weather Advisory until 6 AM CST Sunday for IAZ009-010. Winter Weather Advisory from 6 PM this evening to 6 AM CST Sunday for IAZ011-030.