textproduct: La Crosse

KEY MESSAGES

- Showers and storms expected this afternoon and into the overnight with the highest potential for multiple rounds of storms in northeast IA and southwest WI. Locally heavy rainfall will be possible during this timeframe across northeast IA and southwest WI which may lead to ponding in low-lying areas.

- Additional isolated to scattered storms on Friday afternoon and evening with the potential for some to become strong to severe. Large hail and damaging wind gusts would be the primary threats with any severe storms.

- Above normal temperatures expected next week with highs possibly (40-60% chance) reaching into the 90s for most locations on Wednesday through Friday.

DISCUSSION

Issued at 104 PM CDT Thu Jun 4 2026

Rest of Today - Friday: Showers/Storms Likely, Some Strong to Severe Possible on Friday

Storms will likely begin to develop in areas of northeast IA and southeast MN this afternoon as an axis instability rapidly increases across northern IA and southern MN. Consequently, much of the CAMs agree on developing a line of showers and storms that pushes east throughout the late afternoon and early evening. As we head later into the evening, a secondary axis of 850mb moisture transport surges northward into portions of northeast IA and southwest WI, re- establishing a secondary area of convection. Overall, the environment from a severe perspective is not overly impressive for this afternoon and into the overnight with weak shear profiles and hodographs not being elongated. This combined with deep warm- cloud depths would suggest that the hail risk is virtually zero with any storms. However, given the fairly respectable warm cloud depths of 3- 4km and precipitable waters of 1.75" or greater, would think these storms overnight could produce some fairly efficient rainfall. Consequently, the HREF ensemble mean has rainfall amounts of 1-2" across northeast IA and southwest WI overnight with the 90th percentile showing rainfall amounts of up to 3+", likely where you get redevelopment in this 850mb moisture regime. While most locations should be able to handle 1-2" of rainfall with minimal flooding issues, areas that see training storms could see some isolated ponding in low-lying areas. Eventually, the initial shortwave displayed in deterministic guidance pushes everything eastward towards mid- morning resulting in a lull in precipitation for much of the area.

The key question as we head into tomorrow is exactly how much we destabilize again in the wake of the morning convection. Currently, the consensus in much of the CAMs is to allow for some time to recover during the morning and early afternoon hours on Friday which in turn results in an increase in MLCAPE values across the region to around 1000-2000 J/kg in the RAP by mid-afternoon. Additionally, with a secondary 500mb shortwave trough moving through during the late afternoon and evening. These geopotential height falls will aid in cooling the mid-levels slightly, increasing mid-level lapse rates and decreasing warm-cloud depths. Additionally, some increase in flow aloft with this wave will allow for slightly increased bulk shear values and a corresponding marginal elongation in hodographs in the 3-9km layer. Consequently, would think the hail threat increases as some supercellular structures will be possible in this regime. Additionally, with somewhat steeper low-level lapse rates to around 8-9C/km and some dry air entrainment in RAP/HRRR soundings during the evening, cannot rule out some damaging wind gusts with any storms either. However, given that the stronger low-level jet likely remains south of the local area, thinking the tornado threat is very low as SRH values remain fairly weak accordingly. Consequently, SPC has kept the 2% tornado risk probability south of the local area.

Another point of contention for tomorrow is how much coverage of storms we will see as this is yet again contingent on how much we destabilize during the afternoon which will affect our forcing mechanisms. The main forcing mechanisms that will be in place will be the front associated with the aforementioned secondary shortwave which is somewhat diffuse in our region. This coupled with any convergence near residual differential heating boundaries would be the main forcing mechanisms tomorrow. Given that this forcing regime is fairly weak and there is some shear in the low and mid-levels, thinking storms will maintain a mostly discrete to semi-discrete mode during the afternoon and evening as reflected in the CAMs. So important to emphasize that there is very much a scenario where many locations do not see a storm tomorrow afternoon and evening.

Saturday - Monday: Staying Warm with Additional Precipitation Chances

The aforementioned secondary trough pushes eastward into the Great Lakes by Saturday with upper-level ridging moving into the region. Consequently, expecting minimal precipitation chances for much of the daytime hours on Saturday. As we head later into the day on Sunday, a mid-level shortwave pushes north through the southwesterly flow towards the region. As a result, precipitation chances generally increase Sunday night and into Monday as the trough swings through. Currently, the grand ensemble (GEFS/EC/Canadian ensemble) has high probabilities (70-90%) for measurable precipitation during this period. Overall, given the lack of a more pronounced upper- level wave, shear profiles are not overly impressive with this system at this time. As a result, much of the Machine Learning guidance and joint probabilities for CAPE/Shear in the grand ensemble (GEFS/EC/Canadian ensemble) have very little signal for any severe weather during Sunday night and Monday.

Tuesday - Friday: Trending Hot Late Week

As we move towards the middle and end of next work week, the aforementioned shortwave trough from Monday pushes northeast subjecting our region to increasing geopotential heights and subsequent upper-level ridging. Additionally, low-level flow then shifts to from the south, ushering in additional moisture and warm air advection mid-week. As a result, expecting temperatures to warm further beginning Wednesday as the grand ensemble (GEFS/EC/Canadian ensemble) has respectable (30-50%) probabilities for highs to reach into the 90s by Thursday/Friday. The one interesting thing is the notable difference from the NBM which has very high probabilities (70-90%) for highs over 90, this is likely due to its bias correction and is deviating some from raw guidance. Nevertheless, will still want to watch to see if these higher temperatures verify. Regardless of exactly how high temperatures get, probabilities are high (60-80%) in the grand ensemble (GEFS/EC/Canadian ensemble) for dewpoints to get above 70 degrees during this time period so will certainly feel muggy. Consequently, some probabilities exist (10- 30%) in the grand ensemble (GEFS/EC/Canadian ensemble) for heat indices to reach 100F so could certainly be an impactful period of heat where headlines may be needed. Otherwise, some precipitation probabilities remain during the middle and later part of the week with ample instability in place. However, with the ridge directly overhead, much of the convective initiation would likely be related to small-scale forcing mechanisms so predictability is low at this point.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 605 PM CDT Thu Jun 4 2026

Axis of showers with just a few embedded thunderstorms is located along a CCY to LSE to AUW line and is sliding east as of issuance time - most of these thunderstorms are south/west of LSE so have removed TS from the TAF. Expect this precip to continue sliding east with relatively higher impacts to parts of NE IA and far SW WI as additional thunderstorms and lower visibility reductions are possible there. Overnight, continued increase in low level moisture should lead to IFR ceilings areawide for at least a few hours before slow improvement to MVFR and eventual scattered clouds during the morning hours.

ARX WATCHES/WARNINGS/ADVISORIES

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