textproduct: La Crosse

KEY MESSAGES

- While the local severe weather threat is decreasing, still cannot fully rule out an isolated severe storm before 8pm this afternoon. The tornado threat is quite conditional but still non-zero.

- Cooler and drier for the remainder of the work week with highs in the 50s and lows in the 30s. Warming up next weekend.

DISCUSSION

Issued at 1247 PM CDT Mon Apr 27 2026

This Afternoon: Convective Evolution Details

A 998-mb quasi-barbell surface low structure was noted along a cold front advancing through southwestern MN and northwestern IA early this afternoon, with broad east to southeast flow ahead of these low centroids and veering flow on the south side of these lows behind a warm front. A corridor of clearing developed within the dry slot ahead of the cold front, allowing for some airmass recovery in the wake of our morning convection. While only a few degrees, this insolation was enough to trigger convective initiation along the front shortly before midday in northwestern Iowa. With the 850-mb jet already displaced to the east and surface flow veered to the SSW ahead of the front, the storms are encountering a vertical wind profile unfavorable for sustained updraft longevity, featuring compressed and complex hodographs per HRRR/RAP profiles.

An additional line of convergence along the de-facto warm front lifting into northeastern Iowa could also spark showers and storms over the next few hours. While these storms will develop in a more favorable wind profile featuring looped and elongated hodographs, the lack of daytime heating ahead of the line will result in struggling updrafts if any do manage to get going at all. Thus is the story of our current weather setup--two potential areas of convective development, but neither has both the favorable thermodynamic and kinematic profiles in place to support an organized severe weather threat.

While a very low probability (< 10%) given the relatively progressive nature of the low/front, should sufficient clearing take place ahead of the front, there could be enough 0-3-km MLCAPE and surface vorticity pooled along the front to generate landspout tornadoes with any convection rooted along the boundary. However, the degree of recovery ahead of the front will be key and the window of opportunity for such a setup will be only an hour or two at any given location.

The threat for severe weather departs once the cold front passes, which looks to be between 3pm and 8pm tonight.

Rest of the Week: Cooler and Drier

Broad longwave troughing with multiple embedded shortwaves resides over the north-central U.S. through the remainder of the week, keeping a continued fetch of polar air in place and temperatures roughly 10 degrees below normal. Several of these aforementioned undulations bring periods of clouds and possibly light showers from Tuesday through Thursday, but the probabilities for measurable precipitation is quite low and impacts should be minimal. Lows will be dictated by cloud cover and winds with the surface high pressure centroid remaining upstream, but the need for Frost/Freeze headlines will increase from Tuesday through Friday nights. The pattern shifts for next weekend as ridging builds in, allowing for more seasonal temperatures to creep northward.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1247 PM CDT Mon Apr 27 2026

Predominant MVFR flight conditions across much of the area with some VFR conditions in northeast Iowa and far southwest Wisconsin. All locations will see MVFR to IFR flight conditions due to low CIGS, between 500 and 1500ft, by this evening. These lowered CIGS continue through the overnight before clearing out during the morning on Tuesday. Scattered showers and storms will be possible through the afternoon, ending by early evening.

Visibilities remain mostly in the MVFR range for locations under the stratus deck, during the afternoon then increase to VFR by the evening. Southeast to southwest winds continue into the mid afternoon hours before changing to the northwest as a cold front moves through the region. By midnight, all locations will be out of the northwest with sustained winds of 15 to 25 mph and gusts of 25 to 35 mph. These stronger winds diminish throughout the morning.

ARX WATCHES/WARNINGS/ADVISORIES

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