textproduct: La Crosse

KEY MESSAGES

- Below normal temperatures for the remainder of the week, warming back to around average on Saturday.

- Best chance for areawide frost/freezing temperatures comes Wednesday morning, with the threat for frost shifting east of the Mississippi River for Thursday and Friday mornings.

- Aside from a 10-20% chance for afternoon showers on Thursday and Friday, look for dry conditions for the rest of the work week. Next chance of widespread rain comes late Saturday and early Sunday.

DISCUSSION

Issued at 1240 AM CDT Tue May 5 2026

Today - Wednesday: Dry with Temps 10-15 Degrees Below Normal

A steady fetch of modified arctic air floods southward in the wake of the cold front that passed through Monday afternoon, with 850-mb temperatures today running 10-13C colder than at this time on Monday. We will see deep mixing of the boundary layer both this afternoon and Wednesday afternoon, resulting in the development of daytime cumulus clouds but otherwise result in little sensible weather impacts given the lessening pressure gradient/850-700-mb winds ahead of an approaching high pressure cell.

As with our last round of frost/freeze potential, winds and passing mid to high clouds make the exact temperature forecast less than straightforward. Given the dewpoints in the mid-20s, it would not take much decoupling and clearing to result in rapidly falling temperatures that could fall below freezing in favored low-lying/bog locales and come very close to freezing elsewhere. Wednesday morning is shaping up to be the coldest of the week with the frost/freeze threat shifting eastward later in the week.

Thursday - Friday: Warming, Slight Chance of PM Showers

The axis of the mean longwave trough responsible for our cool weather passes through Wednesday night. While the main reservoir of polar air shunts off to the east, the upstream Pacific airmass struggles to work east of the High Plains as a series of trailing shortwaves rotate around the western flank of the longwave trough. Therefore, while surface temperatures recover somewhat for Thursday and Friday, it won't be until Saturday that this airmass finally penetrates farther into the Upper Midwest.

With increasing lower tropospheric theta-e values, the risk for diurnal showers increases for Thursday and Friday. At this point, there is ample uncertainty on the depth of afternoon mixing, which plays directly into the shower coverage. A quick look at the LREF shows a 40-50% chance of measurable precip on Thursday afternoon, mainly along and east of the Mississippi River, which shifts to mainly NE Iowa and SW Wisconsin along a decaying Front Range low. However, will have to see how the convective allowing models resolve this boundary layer before pushing the official PoP values up that high.

The Weekend: Warmer to Start, Rain Sat PM/Sun AM

Saturday looks to feature the warmest temperatures of the week as a +10C 850-mb thermal ridge translates southeastward through the region ahead of an approaching cold front. The warmest air stays off to the southwest, but highs could touch 70 degrees at many locales with there being a 10-20% chance of highs pushing into the mid to upper 70s if the warm air advection is stronger than forecast. The cold front sweeps down for Saturday PM/Sunday AM and brings with it the next best shot of widespread rainfall, but at this range there is ample spread in some key synoptic variables that will drive the rain risk along the front.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 552 AM CDT Tue May 5 2026

VFR conditions and northwesterly winds expected over the next 24 hours. Cumulus at or around 5 kft and gusts to around 25 knots this afternoon. No flight rules reductions appear on the horizon for several days.

ARX WATCHES/WARNINGS/ADVISORIES

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