textproduct: La Crosse

KEY MESSAGES

- Periodic precipitation is expected through this evening. Potential focuses on a round overnight, another round during the morning hours, and a third round during the afternoon and evening. If everything comes together, the third round may feature severe thunderstorms with mainly a damaging wind risk and a low tornado risk. While we cannot yet dismiss this possibility, the probability of everything coming together has trended downward.

- Quick progression to heavy rainfall keeps confidence for river flooding low (<20%), highest on flashier rivers in northeast Iowa and southwest Wisconsin.

- Colder, slightly below normal temperatures expected through next week. A frost or freeze may occur Friday and Saturday mornings.

DISCUSSION

Issued at 1233 AM CDT Mon Apr 27 2026

Severe storm potential this afternoon

Overnight into this morning, initial rounds of precip look to work their way northeastward to our forecast area ahead of a pair of lead disturbances ejecting northeast of an upper trough over E CO as of 05z. After the morning round, much stronger forcing for ascent arrives via the main body of the upper trough, leading to widespread showers and, given cooling temperatures aloft above increasingly moist low levels, some thunderstorms. This setup may yet provide potential for severe storms - 27.00z HREF joint probabilities indicate a 40-90% chance for sufficient instability, shear, and a lack of inhibition for severe storms to develop. That said, trend across guidance suggests most favorable conditions will be displaced well to our south with the influence of morning showers and mostly cloudy conditions limiting destabilization. Additionally, progged mid and upper level shear characteristics have trended toward a less favorable outcome for supercells to maintain themselves with short hodographs in the 3-6km layer. If enough surface destabilization occurs, cannot rule out a risk for mainly damaging wind given potential for rapid upscale growth due to the large amount of forcing and, given sfc-3km bulk shear values of 35 kts or greater, a stray QLCS tornado.

As for risks from excessive rain, fast motion of thunderstorms should limit flash flooding risks. Concerns mainly focus on flashier basins for eventual river flooding but HEFS probability for reaching minor in these basins has trended downward, now generally 15% or less, as peak rain amounts appear very likely (90%+ per 27.00z HREF) to remain under 2".

Turning cooler after today

Upper troughing becomes predominant over the eastern third of North America, including the Upper Midwest. Temperatures will run around or a bit cooler than normal as a result. Focus on impact continues to mainly look at Friday and Saturday mornings in the wake of another cold front. NBM continues to point toward the possibility for a frost (70-95%) or freeze (25-70%) on these mornings, particularly in Clark/Taylor Counties, with the 27.01z run.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1217 AM CDT Mon Apr 27 2026

VFR conditions will reduce to MVFR conditions as showers overspread the area overnight. These will persist through mid-morning with MVFR vsby reductions and MVFR to potentially IFR cig reductions (40-70% chance in the recent HREF). Winds will generally remain from the southeast for the morning and early afternoon at around 12-18 kts. An additional round of storms during the afternoon with continued low-MVFR to IFR cigs is likely. However, with the recent CAMs not convecting as much as previous runs, have opted to keep with a prob30 at KRST during the afternoon as confidence is low at this point how this will manifest. Regardless, after the frontal passage during the late afternoon and evening that will instigate this secondary round of convection, winds will shift to west/northwesterly at around 15-20 kts with gusts up to 30 kts and continued low-MVFR to IFR cigs through 06z Tuesday.

ARX WATCHES/WARNINGS/ADVISORIES

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