textproduct: La Crosse

KEY MESSAGES

- Drier with near normal temperatures for today and Monday.

- Shower and storm potential returns Monday night and again Tuesday afternoon into Wednesday morning, though the higher chances for rain have been trending south.

- Periodic chances for rain continues through the rest of the work week along with mild afternoon highs.

DISCUSSION

Issued at 119 PM CDT Sun Aug 16 2026

Rest of Today and Monday: Dry with Mild Temperatures

Westerly flow aloft is forecast to prevail today through Monday across the Upper Midwest. In the wake of the frontal passage this morning, drier air has moved in over the region, especially at the surface. Even with cooling temperatures at H850 today, the afternoon highs should be able to reach the upper 70s to low 80s with the surface wind out of the northwest. Given the somewhat drier air at the surface, temperatures tonight should be able to drop into the lower 60s to 50s. Light wind and a shallow moist layer at the surface may lead to fog across portions of the CWA on Monday morning, especially for areas in Wisconsin. Very similar conditions are expected on Monday with highs in the upper 70s to low 80s with light winds.

Monday Night through Wednesday Morning: Shower and Thunderstorm Potential

Mid level moisture moves back over the Upper Mississippi River Valley late Monday afternoon through Tuesday. As this occurs, a shortwave embedded in the westerly flow aloft will move over the region. The combination of these features should lead to scattered shower and thunderstorm development. Severe thunderstorms are not anticipated with this activity since forecast soundings only depict a few hundred joules of CAPE throughout the atmospheric profiles. Any shower or thunderstorm activity that does develop and move east/southeast over the area should dissipate on Tuesday morning across western into central Wisconsin.

After a brief break in the rain chances mid day on Tuesday, another round will be possible on Tuesday afternoon into Wednesday morning as the base of the H300 trough digs south over the Midwest. Unfortunately for those across northern Wisconsin and the northern portions of the forecast area, the better chances (40-70 percent) for rain continue to trend towards the southern half of the area and moreso into Iowa. The latest 16/13z NBM continues to show this trend in the probability for 1 inch of rain or more, which now shows the highest chance is only upwards of 30 percent across northeastern Iowa. That percentage is down from 45-50 percent that the NBM had yesterday at this time. Even though the heavier rain potential continues to shift south, the potential for a storm or two become severe remains across mainly northeastern Iowa into southwestern Wisconsin on Tuesday afternoon into the early evening. Confidence is quite low in that potential at this time, especially given inconsistencies in the model guidance as to where the better lift provided by the shortwave will actually move over. Showers and storms may linger into early Wednesday morning across the far south.

Thursday to Next Weekend: Periodic Rain Chances with Mild Conditions

Northwest flow aloft is forecast beyond Wednesday as troughing remains over the eastern CONUS with a ridge over the Intermountain West. This pattern will likely allow shortwaves to move over the area during this time frame leading to periods of showers and storms, but timing differences leads to low confidence in where and when any rain occurs at this time. Temperatures should remain around to slightly below average going into next weekend.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 632 PM CDT Sun Aug 16 2026

Clearing skies this evening and overnight along with diminishing low level winds brings the potential for IFR/LIFR fog/stratus late tonight into Monday morning. Conditions for these impacts will be most favorable across Wisconsin (30-50%) as slightly drier conditions exist west of the Mississippi River, though the favorable set-up suggests areas of southeast Minnesota and northeast Iowa may also see fog/stratus impacts (10-30%). As far as valley fog at KLSE is concerned, there is certainly potential overnight but also uncertainty regarding how low the visibility gets as there are saturation and light wind layer depth concerns that may hinder efficient valley fog development. Fog/stratus dissipate by 14z Monday morning with light westerly winds and diurnal cumulus around 5kft developing through the afternoon.

ARX WATCHES/WARNINGS/ADVISORIES

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