textproduct: La Crosse

KEY MESSAGES

- Another round of strong to severe storms possible today and tonight, primarily affecting northeast Iowa into southwest Wisconsin with potentially damaging wind and large hail. Isolated tornado threat cannot be ruled out.

- Break in storms and rainfall expected Thursday with a line of severe storms possible Friday afternoon and night. While it remains too far out to nail down details, all hazards look possible with enhanced forcing and tapping into the unstable airmass.

UPDATE

Issued at 420 AM CDT Wed Apr 15 2026

A lower confidence dense fog advisory has been issued for parts of central Wisconsin as fog has been slowly spreading southward from northern Wisconsin throughout the night across already saturated ground. Ongoing elevated convection and an expansive anvil shield have resulted in visibilities bouncing around quite a bit at the automated sites, but there looks to be enough of a break in the storms to have at least areas of dense fog through the early morning.

DISCUSSION

Issued at 1217 AM CDT Wed Apr 15 2026

Ongoing Early Morning Storms:

Tuesday's low level trough abandoned 1" PWATs (GOES derived) across the southeastern 3/4 of the forecast area, permitting the overnight storm threat to lie just south of the forecast area, due to enhanced forcing. Overnight storm initiation observed on DMX/OAX radar is evident of the lingering boundary as DMX VWP light north winds opposes TOP/ICT/EAX 925mb winds of 35+ kts. Fortunately, as the storms progress north towards the forecast area, a drier, colder airmass will limit overall strength. Unfortunately, areas that received heavy rainfall Tuesday night will likely see ongoing storm potential through the early morning hours potentially causing flooding in spots where strongest storms were realized and caused heaviest rainfall.

Strong to Severe Storm Threat Today & Tonight:

Strong to severe storm threat increases across the southern half of the forecast area this afternoon and evening as a potentially deepening low pushes northeast through the Central Plains towards the Mississippi River Valley. Similar to both Monday and Tuesday, meridional advection of the warmer, moister airmass through the late morning hours increases meager initial storm chances before the unstable airmass takes shape through the afternoon. A feedback loop between the deepening cyclone and the frontal boundary raises questions of duration and northern extent of storms. Therefore, overall confidence remains low due to differing solutions in strength of meso cyclogenesis lifting through northeast Iowa into southwest Wisconsin through the afternoon. Ongoing late morning observations of surface winds and progression of synoptic forcing will iron out further details however.

The most locally widespread and potentially strong solution (HRRR/RAP) keeps an open, albeit tightening wave as it nears the forecast area, sufficiently strengthening to abate the drier air attempting to push from northwest to southeast. This solution perpetuates local storm chances across the southern half of the forecast area through the afternoon, evening, tonight, and early Thursday morning. Fortunately, associated temperature sounding profiles show mostly elevated storms, limiting tornado risk with very long, straight, hodographs raising wind threat concerns with secondary hazard of large hail. Although, an isolated tornado cannot be ruled out given stretching of vorticity along the near surface frontal boundary. Furthermore, this solution suggests an initially congealed storm mode through the day becoming linear as the dry punch pushes through tonight as the meso low provides additional forcing for storms through Thursday morning. This is an outlier solution at the current juncture and given the proclivity for the HRRR to jog north/south in its solutions depending on initialization time, bears awareness rather than raw belief.

Higher confidence situation in storms grazing our southern periphery this afternoon and eventually exiting east through the evening hours as the drier air quickly pushes threats south and east of the forecast area. Regardless, all will depend on previous storms which in turn depend on ongoing storms early this morning seen strewn across central Iowa.

Storm Chances Return Friday Afternoon & Night:

A break in storm chances on Thursday is expected as shortwave ridging allows today's drier air to the northwest to advect southeast through the local forecast area. Subsequent longwave troughing, seen in GOES WV imagery over the Pacific Northwest is expected to phase through the Central Plains Thursday, enhancing low level moisture transport into the Northern Plains Friday. Therefore, ample forcing and instability progresses east causing linear storm mode across the forecast area Friday. Unfortunately, machine learning severe weather forecast models have drastically increased local probabilities nearing 50% for the southern half of the forecast area. Current confidence is limited due to influence of diurnal heating to potential timing of frontal passage locally. Will require close monitoring in coming forecasts.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1216 PM CDT Wed Apr 15 2026

Scattered showers and storms will be mainly found south of Interstate 94 corridor. Confidence on the northern extent of these storms were not high enough to include them in the KRST TAF at this time. As far as KLSE, confidence was a bit higher so they were included in the TAF.

For late tonight, fog will likely develop. However, there is still plenty of uncertainty on how dense it will be, so just added some MVFR fog for now.

HYDROLOGY

Issued at 1217 AM CDT Wed Apr 15 2026

Fortunately, heaviest rainfall Tuesday remained south of Monday's heaviest rainfall, easing overall flooding concerns. Therefore, no changes in river flood headlines compared to previous forecasts. Tuesday's rainfall unfortunately slightly affected upstream of more locally flashier rivers in northeast Iowa (Turkey River) southeast Minnesota, and southwest Wisconsin (Kickapoo River). While initial responses on these rivers haven't been overly concerning overnight, subsequent storm chances this morning through tonight raise concern should they frequent these same areas. Similarly, ongoing river flooding in central and west-central Wisconsin is at risk should storms be realized farther north.

Short reprieve in local precipitation chances Thursday ceases for Friday as the anomalously moist airmass returns for strong to severe storms pushing southeast.

ARX WATCHES/WARNINGS/ADVISORIES

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