textproduct: La Crosse

KEY MESSAGES

- A strong winter system is set to move into the region starting this evening and continue through the overnight hours into Thursday morning. This will bring a combination of freezing rain, sleet, and heavy rain. Wintry precipitation is most likely along and north of I-90 where ice accumulations of 0.10 to 0.50 will be possible (highest amounts in North Central Wisconsin).

- On Thursday afternoon and evening, there will be potential of severe weather. The greatest chance will be in southwest and central Wisconsin and parts of northeast Iowa. These areas are under a Slight to Enhanced Risk (2/3 out of 5 risk) by the Storm Prediction Center. The most likely hazards will be damaging winds and the possibility of a couple tornadoes.

- A secondary system will move into the area Friday evening and continue into Saturday. Additional strong to severe storms will be possible in northeast IA and southwest WI. Additional rainfall from this system will likely contribute to further river rises. There is also some potential (20-30% chance) for freezing rain accumulations north of Hwy 29 overnight Friday.

DISCUSSION

Issued at 139 PM CDT Wed Apr 1 2026

Tonight - Thursday: Impactful Winter System to bring Freezing Rain, Heavy Rain, and Severe Storms

We've got a doozy of a winter system set to impact the area later tonight through tomorrow. A strong surface low is beginning to take shape across the Colorado Rockies with a shortwave upper trough approaching from the west/southwest through the day. This will then eject northeast into the Central Plains and eventually the Mid/Upper Mississippi River Valley by late tomorrow. GEFS and EC ensemble members have started to come into better agreement with where exactly this low will track, generally in through Northeast Iowa and into Southwest Wisconsin around 00Z Friday. Widespread precipitation will begin to overspread the area by this evening and continue into the day tomorrow with multiple precip types at play, not to mention the threat for severe storms on the back end Thursday afternoon/evening. Because this is a multi-faceted storm with lots of variables at play and plenty to cover, we're gonna break the details down into shorter time periods.

This Afternoon/Evening (Through Midnight): An upper level cloud shield is already working its way into the region this morning as southwest flow aloft starts to bring in more moisture into the mid and upper levels. The problem initially will be the significant wedge of dry air located between 900-700 mb. Because of this stout layer, have cut precipitation chances for this afternoon, even as we start to see some returns on radar blooming over East Central Iowa. Until we can start to mix some of that moisture down, precipitation will struggle to reach the ground. Through the evening, the column should start to saturate more readily across the region with PoPs really picking up in the 00-06Z timeframe. With areas to the south seeing this saturation first, precipitation should largely start off as rain with a gradual transition to freezing rain/sleet north of the I-90 corridor by late evening.

Overnight (Midnight - 7 AM): This is the period of greatest concern across the area. The profile will be largely saturated so it's not a question of if precipitation will be occurring at this point, it's a matter of what kind. And that's where things get a bit tricky. Surface level fetch will remain out of the east northeast for a large portion of the duration of this storm. Current observations to our north and east across Northeastern Wisconsin show much lower dew points. This then brings wet bulb temperatures much more into effect. So while surface temperatures south of I-90 might not be below freezing, too much dry air at the surface could allow wet bulb temperature to drop below zero, creating more of a sleet/freezing rain impact. One of the failure modes for the forecast would be the wet bulb temperature underachieving and staying below zero north of I-90, causing the bulk of what we think will be freezing rain to end up as sleet. Soundings show a stout, deep warm nose aloft with significant time to re-freeze. The main question is will surface temperatures allow for enough melting to get rain/freezing rain. Along and just south of the I-90 corridor, could see more of a ridge top icing, valley rain event. Surface temperatures further south will be much more finicky and even the smallest changes could lead to higher/lower totals than currently forecast. Regardless of if precipitation type is sleet or freezing rain, elevated surfaces, overpasses, and bridges are at higher risk of seeing accumulating ice. The depending on how quickly things accumulate, the rate of precipitation might overwhelm the surface melting and allow for additional ice accumulations. On the same hand, if precipitation becomes more convective in nature, that might prevent ice from sticking. Its a very complex situation and will be closely monitored through the overnight hours. In any case, this looks to be the time period with the greatest winter impacts.

Thursday Morning (7 AM - Noon): Temperatures will start to warm as the surface low and subsequent warm front start to approach the area. This will allow locations along and south of I-94 to transition to rain during the morning commute, with mixed precipitation lingering for locations across North Central Wisconsin. The Winter Weather Advisory for most of Southeast Minnesota and portions of West Central and Southwest Wisconsin will go through 10 AM as ice begins to phase out with the precipitation turning to all rain. Additional liquid QPF amounts for this time frame generally look to be in the 0.4 to 0.75 range.

Thursday Afternoon/Evening (Noon - Midnight): Because the winter fun isn't enough, we also get a threat for severe storms on the back-end of this storm. As the aforementioned warm front lifts north, portions of SW Wisconsin will be in the warm sector. As the low continues northeast, the cold front will combine with amble moisture and shear across the warm sector and create chances for showers and thunderstorms. The main question will be whether we'll see enough effective instability to work with. Should we clear out some across our south, we may be able to warm enough to allow for us to breach the capping inversion. If we can get enough instability, any storms will have ample shear to support an initial discrete mode before growing upscale into a more linear feature. All hazards will be possible with the magnitude of intensity largely hinging on air mass recovery. Steep low level lapse rates and signficiant low level helicity (01.12 HREF Soundings) suggest that winds and a few tornadoes would be the primary threats with a diminished hail threat. SPC has added Grant County to their enhanced risk (Level 3/5) in their Day 2 Convective Outlook. It will be a narrow window for a small portion of our area but should the ingredients all come together, significant severe weather cannot be ruled out.

Friday - Saturday: Secondary System Impacts The Region with Predominately Rain, Strong to Severe Storms Possible Friday Evening

As we head into the daytime on Friday, northerly flow in the wake of our previous system will keep temperatures on the cooler side with highs roughly seasonable ranging from the middle 40s to around 60. However, with this relatively weak cold air advection near the surface due to the aforementioned northerly flow, this will have implications for severe potential later into the evening. As we head later into the day, the next system that will be needed to monitor is a very pronounced upper-level trough that moves in the Central Plains and transitions to a closed upper-low. At the exit region of this system, a pronounced surface low begins to deepen as it lifts northeastward into the local area with some uncertainty remaining in the exact track with the GEFS favoring a southerly solution and the EC favoring a northern solution.

In any case, at precipitation onset the initial impactful concern will be any storms that develop north of the warm front within the isentropic lifting regime on Friday evening and into the overnight. Overall, with the assumption of the warm front remaining south of the local area, storms would be developing atop a stable layer with a fairly pronounced warm nose present in the recent NAM soundings. In this case, any tornado threat would be non-existent with the cold front/warm front interact being further south in IA/IL. Now this is contrasted by the EC ensemble solutions which keep the warm front slightly north which would push the surface warm front into portions of southwest WI and northeast IA. In this scenario, a damaging wind and tornado threat would be possible, but again there still remains questions on if the warm front will push into the local area at all. If the warm front fails to push into the local area, any tornado or damaging wind risk would be minimal. In either case, elevated instability aloft (around 1000-2000 J/kg of MUCAPE in the NAM) coupled with mid-level lapse rates of around 7 C/km would allow for some hail risk.

In addition to the severe potential, fairly robust 850mb transport and precipitable waters of around 1-1.5" will allow for fairly efficient rainfall production yet again with this system. Currently, the NBM inter-quartile has QPF values across the area ranging from around 0.5" to 1.25" but with 95th percentile values approaching 2" in the NBM, cannot rule out some flooding potential where storms move over areas that received substantial rain from the previous system. Further details about flooding with regards to this system can be found in the Hydrology Section. The only thing that appears to mitigate rainfall amounts to some extent is the overall progressive motion of this system.

Some wintry weather concerns manifest with this system as well Friday night and into Saturday but look to currently be less widespread than with the previous system. With surface temperatures near freezing overnight Friday north of Hwy 29, could see some ice accumulation during this period but overall probabilities in the grand ensemble (GEFS/EC/Canadian ensemble) for a glaze of ice are fairly low (10-30%). In addition to this, cold air advection will work its way in as surface flow switches to west/northwesterly Saturday afternoon. As this occurs, steepening low-level lapse rates to around 7-9 C/km with some instability in this layer will likely result in some shower activity. While surface temperatures will still be above freezing, freezing levels around 1kft and some potential to wetbulb cooler may result in these being snow showers, mainly north of I-94 where there are medium probabilities (30-60%) for measurable snowfall in the grand ensemble (GEFS/EC/Canadian). This would likely be accompanied with some gusty winds with the low- level unstable layer coinciding with a low-level wind field of around 35-40 kts.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1206 PM CDT Wed Apr 1 2026

VFR conditions currently present across the region. An area of precipitation will start to overspread the area later this evening with CIGs dropping quickly to IFR as it moves in. From there, CIGs will generally remain IFR to potentially high-end LIFR through the end of the period. Precipitation will increase into the overnight hours with visibilities decreasing to between MVFR and IFR from the precipitation. KLSE will likely stay in the form of rain as it's down in the valley but KRST could see some wavering between precipitation types. Current best guesses are between rain and freezing rain so will stick with that in this package with further refinements likely with updates. Winds will remain out of a general east/northeast direction through the period with gusts between 20-30 kts possible for much of the evening and overnight hours. Gusts look to taper off by around noon as the surface low begins to approach the area.

HYDROLOGY

Issued at 139 PM CDT Wed Apr 1 2026

Overall rain totals for the first system range from a 0.5 inches to 1.5 inches. Some locations could see slightly higher totals given the convective nature of the rain later in the day on Thursday. Given the antecedent dry conditions, basins should be able to handle this first batch without too much cause for concern. Rises are expected with some of the flashier basins potentially going into action stage before this first round. Unless we significantly over-achieve on totals, this first round should be a healthy rainfall.

In the wake of the first system, additional rainfall amounts of 0.5 to 1.25", localized amounts up to 2 inches, will increase the risk of flooding on some area rivers. While confidence in any flooding is low, confidence for how river rises will manifest will increase further after the rainfall from the system tonight and into Thursday occurs.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory from midnight tonight to 10 AM CDT Thursday for WIZ032-033-041>044-053-055. Ice Storm Warning from midnight tonight to noon CDT Thursday for WIZ017-029. Ice Storm Warning from midnight tonight to 10 AM CDT Thursday for WIZ034. MN...Winter Weather Advisory from midnight tonight to 10 AM CDT Thursday for MNZ079-086>088-095-096. IA...None.