textproduct: La Crosse

KEY MESSAGES

- Scattered showers and some storms (40 to 60%) later this afternoon and evening. The heavy rain threat continues to push further south as there is a 10 to 25% chance of 1" or more of rain.

- More showers and storms are possible (20 to 40%) Saturday afternoon and evening along a cold front.

- After dry conditions for Sunday and Monday, widespread storm chances return Tuesday (50 to 80%).

DISCUSSION

Issued at 144 PM CDT Fri Aug 14 2026

Today - Saturday: Heavy Rain Trending South

Looking at current observations and satellite analysis, there is an MCV that is situated over western Iowa with a boundary positioned over northern Iowa. This boundary will gradually shift northward through the afternoon and evening. The MCV will move eastward providing central and eastern Iowa with a chance for severe storms. As for the boundary across northern Iowa, this will provide the area with scattered showers and some rumbles of thunder during the later afternoon and evening hours. The majority of the instability stays in Iowa, so northeast Iowa has the best chance (20 to 40%) for a thunderstorm developing this afternoon and evening. The trend for any heavy rain has continued to shift further south as the axis of heavy rain is now more along I-80. While the ERO may have a slight risk for excessive rainfall this evening and early overnight, the chances for this happening continue to dwindle given that the better forcing will remain out of our forecast area. The MCV will move eastward across central Iowa and as the LLJ increases this evening, will provide widespread heavy rainfall for eastern Iowa and western Illinois. A few days ago there was higher potential for this band of heavy rain to impact northeast Iowa and southwest Wisconsin, however similar to each of the MCS's that have went south of the forecast area, this too has trended further south.

Some leftover showers are possible (10 to 20%) for the morning and early afternoon, but the better chances for rain on Saturday arrive with a cold front during the late afternoon/early evening. Instability increases as 1000 to 1500 J/kg of MUCAPE build into the region so showers and isolated storms will be possible during this timeframe. There is a little uncertainty on the exact coverage of storms along this front, but for right now the coverage looks to be more isolated (20 to 40%) for showers and storms. Given the instability and weaker shear, if any stronger storm develops, there may be some strong outflow winds from these storms.

Sunday - Midweek: Dry Early, More Storm Chances by Tuesday

Zonal flow becomes the dominant flow pattern through midweek. A surface high passes through the Upper Midwest on Sunday and Monday giving way to mostly dry conditions and high temperatures in the mid 70s to low 80s. Heading into Tuesday, a shortwave trough moves through the region. Moisture tries to get pulled northward as PWATs get into the 1.25 to 1.50" range. Enough 0-6km shear (45 to 60kts) will be in place where the forcing is the best that severe storms could be possible, however this is highly uncertain right now due to differences amongst models in where the best forcing will be, how the cold front from the night before impacts where storms initiate on Tuesday, and how much recovery can take place. AI and ML guidance also highlight this day with some low probabilities for severe weather to occur. Details regarding the storm potential will be refined as we get closer, but this is something to monitor. After the trough exits the region on Thursday, ensemble and deterministic data support a switch back to northwest flow, which could lead to slightly cooler temperatures for the latter half of next week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1230 PM CDT Fri Aug 14 2026

Lurking area of widespread MVFR/IFR stratus and rain potential exists across central IA as of issuance time and should spread back northward and affect both LSE/RST with RST more likely (60%) to see IFR conditions tonight. Rain and TS potential has decreased since last issuance but have still included PROB30 MVFR shower mentions at both TAF sites. Aside from the lower clouds and SHRA potential, expect southeast winds to be predominant along with widespread mid level cloudiness around 15 kft.

ARX WATCHES/WARNINGS/ADVISORIES

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