textproduct: La Crosse

KEY MESSAGES

- Storms likely (70-80% chance) on Wednesday afternoon and into the overnight. Locally heavy rainfall may occurs with these storms which could contribute to flooding in low-lying areas.

- Some storms on Wednesday afternoon and evening may be strong to severe with damaging wind gusts being the primary threat.

- Seasonable temperatures are expected throughout much of the week with highs in the upper 70s to 80s.

DISCUSSION

Issued at 209 AM CDT Tue Jul 7 2026

Today - Thursday: Seasonable, Storms Likely on Wednesday with Some Heavy Rain and Severe Weather Potential

Zonal flow aloft with various shortwave impulses moving through the region will be the main upper-level features for how much of the storm potential will manifest during the middle of this week. Late this evening and into the overnight hours, a shortwave impulse will move across portions of central MN and into northern WI bringing some shower and storm potential to areas north of I-94 as reflected in the CAMs. While the bulk of the heaviest rainfall will likely remain north of the local area with this feature, it will likely establish the thermal gradient and initiating boundary needed for storms on Wednesday.

As we head into Wednesday, this aforementioned boundary will be the main instigating mechanism for convective initiation during the afternoon and into the evening hours across the local area. What will need to be monitored is a favorable axis of 850mb moisture transport that will run along this boundary. Consequently, this would provide a fairly respectable synoptic setup for heavy rainfall in the vicinity of the aforementioned boundary on Wednesday afternoon and into the overnight. This is somewhat dependent on exactly how progressive this boundary is.

Overall the parameter space for heavy rainfall is fairly respectable on Wednesday with precipitable waters approaching around 2" and warm cloud depths of around 3.5-4km. This accompanied with ample instability in the warm cloud layer would suggest that storms will be fairly efficient rain producers. Consequently, the NBM has increased probabilities (30-60%) across much of the local area for rainfall amounts over 1" during this period, with the highest probabilities near and north of I-90. This is a notable shift south in ensemble guidance from previous forecast cycles and will be a trend to watch closely. Additionally, with 95th percentile QPF values in the NBM reaching 2-4" across the region, certainly could see some impressive rainfall totals where storms repeat over the same locations that could result in flooding concerns.

As far as severe weather is concerned on Wednesday, the main signal that is present is some hodograph elongation in the 3-6km layer which would favor some potential storm organization during the late afternoon as the 500mb shortwave moves through. This would favor some supercellular structures with a marginal hail risk and damaging wind threat before a broader cold pool would develop resulting in a multi-cellular to linear mode. Overall the main point of uncertainty with location for both the severe risk and heavy rain risk hinges on how the initiating boundary behaves in response to various rounds of convection. Currently, the trend in the CAMs and ensemble guidance has been to shift the main axis for storm development into much of the local area for the afternoon and evening hours on Wednesday. Storms may linger into Thursday depending on how progressive the boundary passage is, however the probability for severe weather is very low on Thursday.

Friday - This Weekend: Gradually Warmer Through the Weekend

As we head into Friday, temperatures will be near to slightly cooler than normal with highs in the upper 70s to middle 80s. NBM has opted to introduce some low-end precipitation probabilities (10-30%) south of I-90 in light of the NAM having a pronounced shortwave pushing into southern portions of the local area. While the grand ensemble (GEFS/EC/Canadian) has respectable probabilities (40-60%) for measurable precipitation south of I-90, predictability of any systems at this point remains low. Otherwise, upper-level ridging with corresponding geopotential height rises will enable some warming through the weekend with highs returning back into the middle to upper 80s, perhaps even nearing 90 on Sunday.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1243 PM CDT Tue Jul 7 2026

VFR conditions are expected through the rest of the afternoon and into the overnight hours with light southwest winds and diurnal cumulus/mid-level clouds. Late tonight, shower/storm potential increases for those sites north of I-94 (40-70%) and continues through the morning hours Wednesday. Heavy rain is expected with these showers/storms which would result in MVFR visibilities, down to IFR in the heaviest rainfall. Further south, impacts from showers and storms are not expected until near the end of and after the current TAF period as a boundary slowly shifts southeastward.

ARX WATCHES/WARNINGS/ADVISORIES

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