textproduct: La Crosse

KEY MESSAGES

- Rain changes to snow tonight and persists into Wednesday morning resulting in accumulating snow for the local area. Highest accumulations will likely be generally near and north of I-90 where anywhere from 1 to 4 inches may fall. Accumulations of 3 to 6 inches are possible north of Hwy 29 in north-central WI.

- Winds increase early Wednesday morning and afternoon with wind gusts to 45 mph or greater. The combination of windy conditions and ongoing light, fluffy snow will result in near- blizzard conditions at times Wednesday morning.

- Much colder temperatures move in beginning Wednesday and continue for an extended period with highs not getting above freezing for most locations into next week.

- Increasing confidence for additional accumulating snow late Friday and into Saturday. If you have after Thanksgiving travel plans for this weekend, be sure to monitor the forecast closely!

DISCUSSION

Issued at 145 PM CST Tue Nov 25 2025

Rest of Today - Tonight: Rain Changing to Snow Overnight

Today will likely be our last "mild" day for quite some time as a upper-level comma head shown on GOES-19 water vapor imagery and 25.15z RAP 500mb heights situated in the Dakotas pushes eastward towards the local area. As this feature moves into the region, an axis of rain will move through during the afternoon and early evening as depicted in many of the CAMs out ahead of the surface cold front associated with this system. As this robust cold advection pushes into the area overnight, temperatures will drop quickly falling through the 30s and into the 20s. While much of the CAMs keep us in the dry slot during the overnight hours initially with some subsidence behind the cold front, eventually the backside deformation zone of this system will sneak into the area with saturation increasing into the dendritic zone and snow pushing into the local area as soon as 1-3am.

Wednesday: Windy with Snow and Much Colder

During the pre-dawn hours on Wednesday, the aforementioned deformation zone will firmly push into the local area with accumulating snow overspreading much of the area. In tandem with this, winds will dramatically increase as a sharply increasing low-level jet at 850mb positions over the area to 50-60 kts as this system really intensifies right over the local area. The eastward progressing wind gradient aloft in addition is really quite remarkable as in a matter of two counties 850mb winds in the RAP increase from 15 kts to near 60 kts. Consequently, winds may noticeably increase rather rapidly overnight. As a result, have made several changes to forecast and headlines over the past few hours as recent Hi-Res guidance has ramped up the surface winds fairly significantly. The 25.12z HREF has very high probabilities (70-100% chance) for wind gusts over 45 mph with even respectable probabilities (40-70% chance) for gusts over 50 mph. This combined with falling and accumulating snow will likely lead to near-blizzard conditions as joint probabilities in the 25.12z HREF for 1/4 mile visibilities and strong wind gusts are respectable on Wednesday morning (30-60% chance). Needless to say, if you have any travel plans on Wednesday for Thanksgiving consider delaying travel if at all possible until afternoon when conditions will improve as the deformation zone pushes east of the local area.

As far as accumulations are concerned, these will be limited to some extent by the fact that the snow will occur in a fairly short time frame on Wednesday morning. Regardless, the cold advection will push the thermal profile into the dendritic growth zone aloft which will coincide with fairly good vertical motion in the layer. However, given the strong winds near the surface, this will likely fracture any dendrites and thus lower snow ratios. So thinking our snow to liquid ratios here will be around 13-15:1, certainly a drier snow. Considering this, expecting accumulations in between I-90 and Hwy 29 in the 1 to 4 inch range as the 25.12z HREF has high probabilities (70-100%) for amounts over 1 inch in this general area. Higher amounts north of Hwy 29 in Taylor County seem more plausible as probabilistic guidance in the HREF highlights this area for amounts in the 3-6" range as they will likely reside in the deformation zone for a longer period. Consequently, have issued a Winter Weather Advisory for areas near and north of I-90. What is important to reiterate, is that while snow amounts may not be overly significant, the strong winds in combination with falling snow for the morning commute will make travel hazardous.

As this system exits the area, continued windy conditions and northwesterly flow will usher in much colder air into the region. Subsequently, temperatures will struggle to warm any on Wednesday with highs not making it above the freezing mark in most areas, the only exception being in river valley locations. So would expect some slushy accumulations on roadways to occur as a result.

Thanksgiving - Sunday: Staying Cold, Weekend Snow Potential

As we head into the later part of the holiday week, the upper-level trough that instigated this pattern change will slowly pull eastward and subject the local area to a northwesterly flow. Consequently, expecting temperatures to remain on the colder side with a persistent continental polar airmass residing over the region. As a result, much of ensemble guidance keeps highs in the 20s to lower 30s for Thanksgiving and into Friday with this reinforcing airmass in place. With little ridging working into the area, would expect some cloud cover to linger which in combination with steeper low-level lapse rates to around 7-8 C/km and weak 0-3km instability in the 25.12z NAM on Thanksgiving could lead to some flurries and snow showers with the cyclonic flow on the back edge of the upper-level trough, primarily in north-central WI.

Eyes then turn to a potential secondary system to affect the local area from late Friday and into Saturday night. The general conceptual model depicted by deterministic guidance features a relatively weak upper-level shortwave descending out of Alberta/Manitoba, Canada and into the Northern Plains. As this occurs, deterministic guidance has this wave phasing with a southern stream wave in the Central Plains which in turn aids in the development of a strong surface low. The main point of disagreement with this system is exactly when/where this phasing of these waves occurs and how the surface low responds.

Cluster analysis of the grand ensemble (GEFS/EC/Canadian ensemble) gives some hints to the scenarios at play with the more amplified and earlier phasing trough system allowing more room for the attending surface low to push north. In this scenario, the probability for 3 inches or greater (assuming a 10:1 ratio, this will likely be higher) are respectable (30-60% chance) south of the MN/IA state line in the grand ensemble as the low treks slightly further north. The other scenario would keep the surface low weaker, have the phasing occur later and keep the surface low further south which would not favor more robust snow accumulations as much (10-40% chance for 3 inches south of MN/IA state line). Whats also is important to note in the NBM and deterministic runs are more aggressive with the recent NBM having high probabilities (50-80% chance) for 6 inches or greater of snow accumulation south of I-94 over the course of the weekend. Regardless, confidence is quite high (80-100% chance) in the grand ensemble (GEFS/EC/Canadian ensemble) for at least measurable snowfall for much of the region in the grand ensemble so certainly will be the next system to keep our eyes on and if you have post-Thanksgiving travel plans be sure to watch the forecast for the weekend closely!

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 930 PM CST Tue Nov 25 2025

Potent storm system will bring accumulating snows (generally along/north of I-90) and very strong winds to the region overnight through Wed. 1 to 3" currently expected at KRST, likely closer to 1" for KLSE. While the brunt of the storm's impact will shift east overnight Wed/early Thu, stronger winds and perhaps a few flurries/isold -shsn could linger.

CIGS: cigs dropping back to sub 1kft for a few hours into the overnight with RAP/HRRR soundings continuing to suggest a few hundred foot rise into MVFR overnight - and should hold there through the day Wed into Wed night.

WX/vsby: wrap around region of mainly snow will rotate across the local area late this evening/overnight as the parent sfc low moves slowly east/northeast across WI. An hour, maybe two of RASN before transitioning to just SN. Looks mostly 1-2SM in the snow. Some BLSN could impact vsbys into mid morning Wed KRST - depending on how much falls and density of the snow. Will hold with that for now for now. Snow looks to shift east after 15z.

WINDS: very strong/gusty northwest winds into Wed night. Peak winds overnight through Wed morning with gusts of 45-50 kts possible at KRST. Some improvement in the winds moving into Wed evening but gusts could still blow in the mid 20 kts.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory from midnight tonight to 9 AM CST Wednesday for WIZ032-033. Winter Weather Advisory from 3 AM to noon CST Wednesday for WIZ017-029-034-041>044-053. Wind Advisory from 3 AM to 3 PM CST Wednesday for WIZ032>034- 041>044-053>055-061. MN...Wind Advisory from midnight tonight to noon CST Wednesday for MNZ079-086>088-094>096. Winter Weather Advisory from midnight tonight to 9 AM CST Wednesday for MNZ079-086>088-094-095. Winter Weather Advisory from 3 AM to noon CST Wednesday for MNZ096. IA...Wind Advisory from midnight tonight to noon CST Wednesday for IAZ008>011-018-019-029-030.