textproduct: La Crosse

KEY MESSAGES

- Small chances of severe weather late tonight. Main threat would be damaging winds.

- Another round of severe weather possible Monday afternoon and evening. All threats will be possible.

- Surface smoke will gradually exit areas west of the Mississippi River late this afternoon and evening and across the remainder of the area during the overnight tonight.

DISCUSSION

Issued at 100 PM CDT Sun Jul 19 2026

Late Tonight and Monday Morning

The 19.12z models are in general agreement that a mesoscale convective complex will develop over northern and western Minnesota this evening, and then they weaken this complex overnight as the nocturnal jet weakens toward day break. While the models are in agreement of the evolution of the system, they diverremains in the region throughge on the track of this complex. Some move this system along and north of Interstate 94. Others move it southeast through the Upper Mississippi or even further southwest through the western two- thirds of Iowa. The severe weather threat for our area is highly dependent on how early the convection is able to move into the Upper Mississippi River Valley. If the convection can move into the area prior to 4 am, there could be a damaging wind threat. If it moves in after that time, the severe weather threat looks to be greatly diminished.

As far as smoke, the latest HRRR-NCEP shows the near-surface smoke will be gradually improving west of the Mississippi River late this afternoon and evening and in southwest and central Wisconsin during the overnight.

Low temperatures will be in the mid- and upper 60s.

Monday Afternoon and Evening

The convection during the afternoon is highly dependent on where the thunderstorm complex tracks overnight and where its remnant outflow boundary ultimately ends up.

In the more southern solutions, this outflow boundary will likely end up south of Interstate 90 and the convection would initiate more into the evening. With the cold front more parallel, the convection would orientate itself into one or multiple lines segments. Meanwhile, further north of Interstate 90, the orientation with the cold front is more perpendicular and this would result in discrete supercells with all hazards possible.

In the more northern solutions, the outflow boundary would be closer to Interstates 90 and 94. In this scenario, the convection could continue throughout the afternoon and evening due to the lack of a cap. There could be a line or multiple line segments south of Interstate 90 with the damaging winds being the primary concern, and discrete to scattered supercells along the cold front during the late afternoon and evening with all severe weather threats possible.

Depending on how it fast it clears out after the morning convection in northeast Iowa, there could be a need for a Heat Advisory. The current forecast heat indices are 100 to 105F. These could be lower if the outflow boundary from tonremains in the region throughight's convection ends up further south into Iowa. These would be higher if outflow boundary does not get as far south. Due to this uncertainty, held off issuing one for now.

High temperatures will range from the lower 80s to lower 90s.

Monday Overnight

The latest HRRR-NCEP shows some increase in the surface smoke concentrations in the wake of the front where the subsidence is the greatest. However, they would likely only last up to 3 hours. At this time, thinking that these concentrations are not enough to impact surface visibilities.

Low temperatures will be in the mid- and upper 60s.

AVIATION /18Z TAFS THROUGH 12Z MONDAY/

Issued at 100 PM CDT Sun Jul 19 2026

MVFR to IFR visibilities and ceilings due to smoke from Canadian and northeastern Minnesota wildfires will remain in place through this afternoon. These will then become VFR as the smoke moves out of southeast Minnesota and northeast Iowa during evening and across the remainder of the area overnight tonight.

ARX WATCHES/WARNINGS/ADVISORIES

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