textproduct: La Crosse

KEY MESSAGES

- Showers and scattered storms through early this afternoon. The coolest temperatures for the upcoming 7-days will be today with high temperatures ranging from the upper 60s to around 80.

- Severe weather threat looks lower for Sunday afternoon and night.

- Above-normal temperatures expected next week. There may be even some record warm lows in Iowa and Illinois early next week and during the late week.

DISCUSSION

Issued at 106 AM CDT Sat Aug 29 2026

This Morning and Early Afternoon

A shortwave trough over southwest Minnesota will move east overnight and this morning. As this system approaches, the 850 mb moisture transport will gradually increase on the nose of a 30-40 knot nocturnal jet. Showers and maybe a few storms will move into northeast Iowa and southeast Minnesota after 3 am, and western Wisconsin around 6 am. These showers and storms will move out of northeast Iowa and southeast Minnesota around noon and western Wisconsin by 3 pm.

The 29.00z HREF has a mean 24-hour rainfall of a 0.25 to 0.50 inches from northeast Iowa northeast into central and north- central Wisconsin, and up to a quarter-inch in southwest Wisconsin. The ensemble localized probability-matched mean suggests that there could be some localized rain totals of a half to 1-inch.

In the wake of this system, some of the CAMs are continuing to show that subsidence in the wake of this system might bring stronger winds (up to 45 mph) between 925 and 850 mb to the surface mainly west of the Mississippi River. The evening shift used the RAP to raise the Issued at 106 AM CDT Sat Aug 29 2026wind gusts into the 30 to 40 mph range.

There is a trailing shortwave trough over central South Dakota. There is ample instability ahead of this wave at the apex of a strong ridge. This has resulted in some strong to severe storms. The CAMS are in general agreement that this shortwave will move southeast of the area late this morning and afternoon. Thoughts are that these storms will gradually become more elevated as the night persists and this would likely continue through much of this morning.

Rain-cooled air will slow the warming this afternoon. High temperatures will range from the upper 60s in north-central Wisconsin to around 80 west of the Mississippi River.

Tonight and Sunday morning

The 500 mb longwave ridge axis will move east into the Upper Mississippi River Valley. The nose 30-40 knot 850 mb jet will develop during the evening ahead of another shortwave trough moving east on the north side of the 500 mb ridge. It continues to look like the better chances of showers and storms will be along and north of Interstate 90. As the the nocturnal jet gradually veers overnight, the showers and storms will move out of the area on Sunday morning.

While the 0-6 km shear is greater than 40 knots north of Interstate 94 tonight, the most-unstable CAPES are less than 500 J/kg, so the chances of organized severe weather looks low.

Low temperatures tonight will be around 60 north of Interstate 94 and in the 60s across the remainder of the area.

Sunday afternoon and night

On Sunday afternoon and night, the ridge axis will build north across the Upper Mississippi River Valley. A frontal boundary will be initially near Interstate 90 in the morning and then move gradually north during the day. As this occurs, the strong westerlies will shift northward into northern Minnesota and northern Wisconsin. This should result in lesser 0-3 km and 0-6 km shear across the Upper Mississippi River Valley. Thus, thinking the marginal risk of severe weather should be shifted further north.

High temperatures on Sunday will range from the upper 70s to mid-80s. Low temperatures on Sunday night will range from the mid-60s to lower 70s.

Monday through Friday

A northern stream shortwave trough will gradually flatten the ridge on Monday night and Tuesday. This will leave the Upper Mississippi River Valley on the northern periphery of this ridge through mid-week and then there are some indications that this ridge may build northward across the region for late in the week. Periodic showers and storms look possible during the mid- week.

Temperatures will be likely above normal through this time period. High temperatures will be mainly in the 80s. There may be even a few lower 90s. Low temperatures will be in the 60s and lower 70s. There will be a possibility of near record warm lows across Iowa and Illinois early in the week and again during the late week.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 555 AM CDT Sat Aug 29 2026

A shortwave trough will bring showers and scattered storms to the area through mid-afternoon. The rain will affect KRST through 29.18z and KLSE through 29.20z. This rain may result in MVFR ceilings and visibilities at times. In addition, there could be prevailing MVFR ceilings north of Interstate 94 this afternoon. Additional showers and storms will be possible north of Interstate 94 tonight.

ARX WATCHES/WARNINGS/ADVISORIES

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