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 an unstable airmass in place.

DISCUSSION

Issued at 121 PM CDT Wed Apr 15 2026

Severe Storms Possible Again Today

Another day, another chance for severe weather to impact the Driftless Region. Early this afternoon an elevated supercell was moving across Western and Central Iowa, riding a quasi-stationary boundary north and east along a gradient of MLCAPE. As it's generally on the cool side of the front, this is expected to continue to pose more of a large hail threat given steep mid level lapse rates and sufficient CAPE in the hail growth zone. Further east across Northeast Iowa and Southwest Wisconsin, lingering cloud cover and light showers have allowed the area to remain sufficiently capped and overall stable. As these finally start to move to the east/northeast, we may see a small window of destabilization. Latest mesoanalysis trends show meager destabilization before storms really start to fire later this afternoon as ascent from an ejecting upper trough across the Central Plains increases across the area and interacts with the surface boundary. Moderately strong mid level lapse rates should still promote between 500-1500 J/kg of MLCAPE, even with the continued cloud cover. The main threat with any storms would be large to potentially very large hail. There's also potential for splitting supercells given the significantly elongated straight hodographs expected with this activity. The main question will be how long storms can stay semi-discrete before either lifting north of the boundary or growing upscale into a cluster as effective bulk shear between 30-50 kts will promote upscale growth. These storms will also be effective rainfall producers as pWats continue to increase with 850 mb moisture transport into the region. Another 0.5-1.5 inches of precipitation is expected with across portions of SW and Central Wisconsin, areas that have already seen ample rainfall and flooding over the past couple of days. Have issued a Flood Watch for this area starting at 4 pm and continuing through 7 am tomorrow morning as areal flooding may form with exacerbation to already ongoing areal/river flooding expected.

Even More Severe Weather Friday

After a brief reprieve from severe storms Thursday, we re-enter the severe weather fray on Friday. A deep trough over the Rockies is expected to start sliding east with ascent out ahead of it increasing across the southwesterly flow aloft. At the surface a family of lows will stretch south from the Dakotas into the Central Plains and Colorado Rockies with a cold front connecting them. A broad warm sector will develop across the Mississippi Valley ahead of this cold front which will allow for convective development Friday afternoon as ascent aloft increases locally and interacts with the eastward moving cold front. A highly unstable air mass should be in place with forecast instability in the 2000-3000 J/kg range. Effective shear will be ample enough to support initial supercellular development before upscale growth occurs and forms a more linear structure. A 40-60 kt jet in the 850-700 mb layer will also help to promote low/mid level hodograph curvature and strength, increasing the potential for tornadoes with the supercells. The main question will be how far north can the moisture and more ample instability make it ahead of storm initiation with greater uncertainty in northward extent. Far southern portions of NE Iowa are currently in a Day 3 Enhanced Risk (level 3/5) with the rest of the local area in a level 2 Slight Risk.

Much Cooler This Weekend, Snow Chances??

Behind this cold front, cold air advection will be rather strong given the tight pressure gradient behind the departing surface low (moving northeast into Ontario). With the strong cooling expected in the wake of the front, any post frontal precipitation may potentially turn to a rain snow mix Friday night into Saturday as lows drop into the low to mid 30s. No accumulations are expected as surface temperatures will remain quite warm after the stretch of 70+ degree temperatures we've seen as of late. Any snow should melt on contact pretty quickly. Precipitation will gradually come to an end through the day with high temperatures in the 40s, 20-30+ degrees cooler from Friday. Beyond Saturday, it looks like a dry forecast with temperatures warming back into the 50s and 60s by mid week - a much welcomed relief after an active week of severe weather!

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 639 PM CDT Wed Apr 15 2026

More widespread storm chances seen shifting east through the southern half of the forecast area affecting smaller airports from northeast Iowa into southwest and central Wisconsin at 16.00Z TAF issuance. While this area is expected to continue exiting east, the upstream low center raises concerns for additional scattered storms somewhere across the forecast area, potentially farther north affecting local TAF sites (KLSE/KRST). Therefore, have included PROB30 TS at KLSE given current confidence in location but will require further investigation as storms continue developing through central Iowa.

Similar to previous overnights, expect VFR-LIFR shallow fog to develop in spots affecting select sites where it thickens. VFR expected through

HYDROLOGY

Issued at 121 PM CDT Wed Apr 15 2026

A Flood Watch has been issued for Southwestern Wisconsin and portions of West Central Wisconsin as yet another round of showers and thunderstorms is set to impact the region. With additional .5- 1.5 inches of QPF expected from this activity, areal and river flooding is expected to worsen. The main basins of concern look to be the Kickapoo, the Yellow (WI), Lemonweir, and Wisconsin Rivers as these areas have already been hit hard over this past week. Major flooding is either already occurring or expected to occur for the Yellow River at Necedah, Castle Rock Dam on the Wisconsin River, and the Lemonweir River in New Lisbon. Flooding along the Lemonweir has already lead to some road closures in portions of Juneau and Monroe counties with additional rain likely to exacerbate ongoing problems. Additional rainfall is also expected Friday as a line of storms moves through the entire area, again impacting portions of SW and WC Wisconsin. QPF totals with that system remain a bit more uncertain - though another 0.5 -1.5 inches certainly looks possible.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Flood Watch through Thursday morning for WIZ042>044-053>055- 061. MN...None. IA...None.