textproduct: La Crosse

KEY MESSAGES

- Scattered shower and storms move through the area through the morning and early afternoon with some potentially on the stronger side, especially for areas in southwest Wisconsin.

- Seasonal temperatures continue into next week with highs in the 70s to lower 80s.

- Dry weekend with the next potential round of storms coming Tuesday and Wednesday of next week.

DISCUSSION

Issued at 1205 AM CDT Fri Aug 21 2026

Today: Storm Potential

Invigorating upper level northwest flow is driving storm development upstream through central Minnesota overnight, focused along an enhanced area of low level convergence on Central to Northern Plains VWPs. A meager open perturbation well to the north over Lake Superior on GOES derived upper level wind plots has prevented storms spreading as far south as the local forecast area as subsequent supplementary forcing from the low level frontal boundary trails well behind, struggling to traverse the Missouri River Valley into west-central Minnesota. Eventual synoptic assistance from an additional perturbation crossing the International Border from Saskatchewan into Northern Dakota will drive said frontal boundary southeast through the Upper Mississippi River Valley.

Ahead of a cold front that will push through the region this morning and afternoon, a few weak perturbations and a slight increase in the nocturnal LLJ will help to initiate some storms, as recent CAMs have supported, during the early morning hours. With limited instability and minimal shear and mid-level subsidence, these showers and storms should remain below severe limits, however small hail and gusty winds will be possible. Heading into the mid morning to early afternoon timeframe, the cold front will begin to enter our CWA. Dependent on diurnal timing and southeastern extent of this low level frontal boundary across the forecast area, these prefrontal storms will likely continue for some of the local forecast area primarily from northeast Iowa into southwest Wisconsin. While instability is expected to be ample, around 2000 to 2500 J/kg of MLCAPE, there will be minimal shear present. With the increase in instability though and the fact that any storms that due form along and just ahead of the cold front will be in their developing phase, a storm or two could have severe hail up to 1". The better severe ingredients remain in southeast Wisconsin and northern Illinois and back west into Nebraska and southern Iowa. All precipitation chances diminish by the early afternoon. Total rainfall from these storms could be over 1" in some locations as the 00Z HREF LPMM has some spots of over 1" along the I-94 corridor and in far southwest Wisconsin.

Saturday - Midweek: Dry Early, Storms Return Tuesday

Northwest flow returns to the region as a trough amplifies to our east and the ridge sets up to our west. This ridge decays as it moves eastward into early next week. With our region in between these two features, we look to be mostly dry and slightly cooler through the weekend until the ridge breaks down on Tuesday. High temperatures stay in the low 70s to low 80s from Saturday through Monday. Storm chances return Tuesday as a trough moves down from northern Minnesota. The latest GEFS and EPS have a widespread 60 to 90% chance for measurable storms. The exact timing and placement details of this rain will be hammered out as we get closer to the event.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1217 AM CDT Fri Aug 21 2026

Primary concern over the next 24 hours will be potential for TS over the next 12 hours as a cold front pushes southeast. TS is likely (60-80%) overnight northeast of a EAU-82C line but could (30%) extend to near LSE. Have retained PROB30 mention and adjusted timing compared to previous TAF cycle. Probability is too low to keep a mention at RST (20%). Otherwise winds will turn clockwise from out of the southwest to out of the northwest over the next 12 hours as well and continue to be out of the northwest at 10-15 knots Friday afternoon.

ARX WATCHES/WARNINGS/ADVISORIES

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