textproduct: La Crosse

KEY MESSAGES

- Low storm chances across the south this evening (7-10 pm) bring a small chance for hail to quarter size and damaging wind gusts. This is a very conditional threat based on storms being able to form in northeast Iowa and southwest WI. Storm chances increase again Tuesday morning around I-90 and south with a large hail threat again.

- The first of two strong weather systems moves through the area midweek and probabilities are increasing for wintry impacts Wednesday night into Thursday. Chances are increasing for snow and ice accumulations just south of I-90 and northward, with rain south. There is some potential ice accumulations to reach 1/4 inch (30%) northeast of I-94. Uncertainty remains moderate.

- The second strong system moves through the Midwest late in the week and into the weekend. The area looks to be on mainly the warmer side of this storm with rain. The storm track will determine the wintry weather location, but right now the probabilities for accumulating snow appear more toward central MN and northern WI, with some wintry mix possible (30%) north and west of La Crosse.

DISCUSSION

Issued at 142 PM CDT Mon Mar 30 2026

Storm Chances Tonight and Tuesday Morning

A predominant zonal flow continues across the area into Tuesday with a number of embedded shortwave troughs shifting through. A stationary frontal boundary parallels I-90 with southerly flow moisture advecting higher dewpoint air in, and instability is growing slowly south of the front. One of the limiting factors however is a very strong capping inversion in place. The latest HRRR/NAM3km convective inhibition across southwest WI / nern IA minimizes at 125 J/Kg preventing surface-based storms, favoring more south of the forecast area closer to the I-80 corridor. Steep, impressive lapse rates aloft due to an elevated mixed layer presence aloft is favorable for updraft intensity should the forcing be enough to initiate elevated storms. A weak low- level moisture transport convergence area does shift through northeast IA and southwest WI from 5-9 pm. So, a conditional threat based on the forcing saturating aloft and leveraging the steep lapse rates. Right now, it seems there is a very small chance (10-20%) for a storm to form. A quarter sized hail report and downburst in a very dry subcloud layer cannot be ruled out (10-20%) for swrn WI and nern IA this early eve before moving east.

Tuesday morning seems to have a bit better elevated instability across the area south of I-90 as the stationary front becomes a cold front and moves southeast through the area. The elevated instability is over 1000 J/Kg with steep 400-700 mb lapse rates (>8C/km) should saturdation occur aloft and storms be realized. This seems to be a better chance for large hail, with 30 kts of bulk shear in the 2-7km layer, but again conditional on the saturation occurring. Recent RAP runs indicate a slightly increasing moisture convergence signal but most convergence over central/east WI. The 30.12Z CAMS are quiet, sans the latest HRRR runs that suggest some I-90 storms. The main window for this would be about 4-9 am. With the conditional nature again, have rain chances at 30%.

Impactful Late Winter Storm Possible Midweek

Confidence is pretty high that the area will be in the storm track of a stronger low pressure area ejecting northeast from the Texas Panhandle. Precipitation looks to be a sure bet Wednesday night through Thursday. The cold air ushered in by Tuesdays cold front will set the stage for wintry precipitation including ice and snow accumulations. A very warm layer aloft is coming in Wed night with MaxT aloft getting to 5-6C. Surface temperatures look like they will be right near freezing for much of the area south of I-94 which will have a huge impact on rain versus freezing rain / icing and snow areas - and their accumulations. Heading into April, temperatures near freezing cause a pause for going too bonkers with ice accumulations. A clear signal is that the river valleys will be warmer and any icing would be much reduced there. But the track of this system will govern the precipitation types...and moderate uncertainty exists in the track and surface temperatures.

The current consensus in the wintry mix and icing probabilities are in a wide band along I-90, slightly into nern IA and southwest WI (Richland/Crawford) and north. Rain would fall south of that area. NBM probabilities from the 30.06Z NBM run suggest a 40-70% chance of one-tenth of an inch of ice in that region, with the higher probabilities northeast of I-94 where the coldest temperatures below freezing would reside. This area could have the highest accumulation of ice due to favorable surface temperatures with the NBM probabilities around 30% for one-quarter inch of ice for Clark and Taylor counties. There could also be a few inches of snow Wednesday night there prior to the icing.

This system has very anomalous moisture inflow of over an inch of precipitable water (1-1.25") which is near the daily max at KDVN per SPC climatology. Liquid equivalent amounts across the south look to be in the 1.50-2.0" range with the latest GEFS and ECMWF ensembles showing 10-25% chances of 2" near Dubuque. This would fall mostly as rain and cause river rises on the Kickapoo river. These precipitation totals decrease northwestward, with 50-70% chances of 1+ inches at La Crosse (in mixed precipitation). So, a wet system.

Will begin to ramp up the messaging on this storm using probabilities as they provide a nice way to describe the possible impacts yet temper it with uncertainty both in surface temperature and storm track. The NBM probabilities of one-tenth of an inch of ice also highlight the lesser accumulations in the river valleys.

Another Weather System Next Weekend

General consensus exists on another strong system ejecting out of a longwave trough developing over the western U.S. this week. The system is currently over Alaska, far away, but many of the ensembles of the 30.00Z LREF have a stronger cyclone moving through Friday and Saturday. The area looks to be on mainly the warmer side of this storm with rain. The storm track will determine the wintry weather location, but right now the probabilities for accumulating snow appear more toward central MN and northern WI, with some wintry mix possible (30%) north and west of La Crosse. It is way out in the timing and there is a moderate amount of spread on the track...but something to keep an eye on.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1229 PM CDT Mon Mar 30 2026

VFR conditions should prevail for the next 12-15 hours before stratus potentially develops in central WI and spreads southwest across the area. Guidance suggests stratus will be in the 500-1500 foot layer so have gone with low end MFVR mentions with this update and can move to IFR later if needed. A thunderstorm or two may (25%) occur in far SW WI this afternoon and some showers may (30%) occur in the 12z-18z Tuesday time frame across much of the area but confidence on TS is too low to add a mention to the definite MVFR conditions already included due to stratus.

HYDROLOGY

Issued at 142 PM CDT Mon Mar 30 2026

Rain amounts Wednesday night and Thursday could approach 2 inches in southwest Wisconsin. Should this occur, and the precipitation type remain as all rain, stream and river rises are possible on the Kickapoo river late in the week.

CLIMATE

Issued at 1248 AM CDT Mon Mar 30 2026

Near record highs Today (Record/Forecast):

Rochester, MN 77 (1967) / Fcst: 74 La Crosse, WI 80 (1910) / Fcst: 76

ARX WATCHES/WARNINGS/ADVISORIES

WI...None. MN...None. IA...None.