textproduct: La Crosse

KEY MESSAGES

- Clouds gradually depart this afternoon with overnight fog and clearer skies for Thursday.

- Temperatures warm back up to around average for the end of the week into next week.

- Several rounds of showers and storms possible nearly daily starting Friday afternoon and going through early next week. Main risk from these storms may come in the form of heavy rain as storms may track over the same areas for multiple days.

DISCUSSION

Issued at 129 PM CDT Wed Aug 5 2026

This Afternoon - Thursday: Dry and Seasonal

Isolated showers gradually depart northeast Iowa and southwestern Wisconsin this afternoon with most areas staying dry. Clouds likewise depart with fog becoming increasingly likely for areas that received rain last night and this morning, mainly along and southeast of a Charles City, IA to Wisconsin Rapids, WI line. Much of the MOS guidance is hinted at visibilities of 1/2 of a mile or less by tomorrow morning and the conceptual model fits a potential dense fog scenario given the new precipitation and antecedent cloudy skies during the day, which will allow for saturation to happen quicker this evening once the clouds clear.

With the lower tropospheric theta-e ridge having slid further southeast into Iowa and Illinois, mid-level ridging will take control for tonight into Thursday. Once the fog burns off during the morning, look for sunny skies and warmer temperatures rising back to near average.

Friday - Early Next Week: Periodic Storms w/ a Heavy Rain Threat?

Cyclonic flow lingers across south-central Canada from Friday into early next week, with the local area transitioning to zonal/quasi-northwest flow on the southern periphery of this cutoff low. Multiple perturbations eject from this low across the region, starting late Friday and continuing into early next week. The zonal lower tropospheric baroclinic zone looks to remain situated somewhere between Iowa and southern Minnesota during this period, oscillating periodically with each passing wave of storms. The exact position of this boundary will dictate the track of our storms and how the next day's storms will evolve.

If the boundary happens to stall over the same areas for multiple days, we could see a heavy rainfall/flooding threat materialize. Thankfully, there is not an anomalously moist airmass in place, so any heavy rain risk will be more driven by mesoscale processes and rely on storms training over the same locales. Even the global ensembles are not terribly excited for rainfall with little signal for over 1" of rain--but conceptually the pattern is in place for it to occur. With an increasing shear profile late in the weekend and early next week, the risk for more organized and stronger convection likewise increases. However, like with the heavy rain risk, any severe weather risk remains tough to pin down at this time.

With the increasing risk for convection each day and weak north to east flow to the north of the boundary, the temperature forecast for the weekend and early next week has cooled modestly from what was being forecast a few days ago, with highs at or slightly cooler than average.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1225 PM CDT Wed Aug 5 2026

Primary concern over the next 24 hours is the likelihood (70%) of fog across much of NE IA and SW WI tonight into early Thursday as light winds through the lower 4 kft of the atmosphere occur and skies clear. Expect IFR/LIFR conditions, particularly in river valleys, so have included this at LSE. Expect additional adjustments over the 2 TAF cycles. Otherwise, winds will generally light and variable until late in the period when southerly winds at 5 to 10 knots return.

ARX WATCHES/WARNINGS/ADVISORIES

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