textproduct: La Crosse

KEY MESSAGES

- First of two systems moves into the region today and continues through Friday with rain transitioning to snow. Uncertainty remains in snow totals as they will be highly dependent on when rain fully transitions to snow. An earlier transition to all snow could lead to higher accumulations (2+ inches) across SE Minnesota and NC Wisconsin. - The second winter system moves into the region late Friday night and into Sunday morning with accumulating snow likely. There is a 40-70% chance of at least 1" of snow for the forecast area with the higher probabilities east of the Mississippi River.

DISCUSSION

Issued at 313 AM CST Thu Jan 8 2026

Today - Friday: Rain Transitioning to Snow

Early this morning, a 500 mb shortwave trough was moving through the Southern Rockies, heading northeast into the South Central Plains. At the surface, a low pressure system was deepening in the lee of the Colorado Rockies. Along with the upper level shortwave trough, this surface low is expected to eject northeast into the Central Plains and eventually into the Upper Mississippi Valley by around 00Z tonight. Warm, moist southerly flow in the low levels have allowed many locations outside of the river valleys to stay above freezing overnight which will allow daytime temperatures to climb into the upper 30s to mid 40s (some upper 40s possible across far SW Wisconsin). As the surface low starts to approach the area, precipitation will start to move in from the south late this morning with PoPs increasing steadily through the afternoon. The mild temperatures will allow all this precipitation to start as all rain. While we're not expecting these rain showers to be convective in nature, they will provide some moderate rainfall, which will likely lead to ponding and runoff as it encounters frozen ground. This will also lead to some river rises and the potential for ice jams down the line as ice starts to break up on rivers that are currently frozen. Current rain totals generally range from 0.25-0.75 inches with locations across NE Iowa and SW Wisconsin (closer to the center of the low) seeing better chances of rainfall approaching 1 inch.

As the low starts to depart from the region, winds will quickly shift to the north. This looks to complicate matters when it comes to precipitation type. 00Z HRRR/NAM soundings show a generally isothermal profile in the lower levels of the atmosphere as the column saturates. As the colder air from the north starts to cool temperatures, this will lead to a transition from all rain to a rain snow mix. Unfortunately temperatures seem to hover right around the 0 deg C isotherm for a couple of hours before cooling entirely below freezing and transitioning to all snow for most overnight. Current forecasts have a best guess time for this transition to a mix to occur between 8-10PM, starting across SE Minnesota and WC Wisconsin before gradually expanding eastward. How much snow that accumulates will heavily rely on when the transition to all snow occurs as the rain/snow mix will melt any accumulations. Current thinking is that as the low moves off and the frontogenetic (deformation) band starts to wane, precip will lighten through the overnight hours leading to lower accumulation totals. Should the transition to all snow start earlier than current forecasts, snow totals would end up being higher than the current trace to 1 inch totals currently expected for most (outside SW Wisconsin). Places most likely to see totals at or above 1 inch would be SE Minnesota and North Central Wisconsin (30-60% chance). There are some possibilities for 2+ inches in this same area should the transition happen sooner (10-30% chance). 00Z HREF members seem to be leaning towards a slightly earlier transition compared to previous runs, leading to a slight increase in overall totals. Again, these totals will be highly dependent on how quickly we can cool below freezing and fully transition to snow so we will be paying close attention to surface observations this evening.

Friday Night - Saturday: Another Round of Snow

In case one winter system wasn't exciting enough, we have yet another one to look forward to right on the tails of this first one. As the first shortwave trough exits to the northeast, two more troughs wait in the wings: one to the north across the Canadian Plains and the other one the south across the South Central Rockies. These will both make their way towards the forecast area during the day on Friday, coming into phase with one another over the Upper Midwest Saturday morning. Given the abundant synoptic lift from the mid/upper level lows, a slight increase in moisture, and cooler temperatures aloft, an area of snow is expected to move into the region starting early Saturday morning.

Overall totals have come down some from yesterday given that the surface low and the bulk of low level support will be well displaced to the southeast of the upper low, likely forming in the left exit region of an enhanced 500 mb jet max across the Mid Mississippi/Ohio River Valleys. The continued southerly track of the surface low will limit the intensity of snowfall across our area. Current forecast totals generally reside in the 1-3 inch range, with the highest totals east of the river in Wisconsin. Probabilities of seeing 2+ inches of snow have dropped below 50% for nearly the entire area (apart from Juneau/Adams counties in our far east). Ensemble outliers in the EC/GEFS have also come down with no SOT being shown anymore with the EFI. This is looking less 'boom or bust' snow event and more like a normal midwest winter snowfall. This snow is expected to be lighter/fluffier than normal given the 100-150 mb residence time in the DGZ lending to higher snow ratios (15-18:1). As the upper low slides to the east late Saturday into Sunday, snow showers will gradually end from west to east during the early morning hours Sunday.

Sunday - Early Next Week: Cooler To Start, Drier

We'll get a short but much needed breather Sunday and Monday as we transition to northwest flow aloft behind the departing upper low. Conditions should stay dry with cooler but still near normal temperatures returning to the area for Sunday with highs in the 20s. The cool temperatures will be short-lived however as southerly surface flow returns by Monday, bringing highs back into the 30s to low 40s. Low chances for precipitation return Tuesday and Wednesday with some potential weak shortwave troughs passing through the northwest flow aloft. Cooling temperatures mean this could be a rain/snow mix but its still early and many details are certain to change.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 520 AM CST Thu Jan 8 2026

CIGs remain largely VFR across the area with some MVFR to LIFR visibilities from FG/FZFG present (mainly across WC Wisconsin). Visibilities will start to improve later this morning with both terminals expected to be at VFR for a time. Rain will then move in from the south, impacting the terminals starting in the early/mid afternoon and continuing into the overnight hours. This will bring degraded visibilities (MVFR to IFR) and significantly lowered CIGs (IFR to LIFR) across the area. Later this evening, rain is expected to begin transitioning to snow, starting across SE Minnesota and WC Wisconsin before spreading east. This transition should be more noticeable at the KRST terminal with a best guess on the precip changeover timing made for this package. Precipitation should wane by the end of the period with both sites likely dry by 12Z Friday morning.

Winds out of the south will remain light through the morning before quickly transitioning to a more northerly direction by this afternoon. Speeds are expected to pick up to between 10-20 kts by this evening with gusts in the 20-30 kt range late tonight and continuing through the overnight hours.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Dense Fog Advisory until 10 AM CST this morning for WIZ017-029- 032>034. MN...Dense Fog Advisory until 10 AM CST this morning for MNZ079. IA...None.