textproduct: La Crosse

KEY MESSAGES

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

- Freezing temperatures expected early Wednesday morning before 8 am for locales along and north of the I-94 corridor. Near freezing temperatures for the rest of the local area.

- 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 630 PM CDT Tue May 5 2026

Tonight - Wednesday: Cool and Dry

Northwesterly surface flow is ushering in a modified Arctic airmass that is much cooler and drier than what we've been seeing for much of this spring so far. Fair weather cumulus and substantial low level mixing is allowing temperatures to stay in the upper 40s to low 50s with dew points steadily dropping into the teens. Though the airmass is much drier, the cooler temperatures are keeping the worst of the fire weather concerns at bay with most locations seeing RHs bottom out in the 25-35 percent range. This cool and dry trend will continue into tomorrow as a robust high pressure system drops south into the plains with our area remaining on its fringes.

The main concern for the near term is the potential for frost/freeze conditions tonight and Thursday morning. As the boundary layer decouples and the nighttime inversion sets up, winds will steadily decrease into the overnight hours. The diurnal cumulus from earlier in the day will erode and allow for more clearing as the night progresses. Both of these along with the dry airmass will allow for ample radiational cooling across much of the region tonight. Areas along and north of the I-94 corridor and notorious cold air drainage spots will likely see lows fall into the mid to upper 20s with most other locations hovering right around or just above freezing. As such have issued a Freeze Warning for counties along and north of I-94 with a Frost Advisory elsewhere. Frost and freeze potential will need to be evaluated further for the coming days as the bulk of the polar airmass gets shunted to the east of our area. Both the 05.00 LREF and 05.07 NBM have decreasing probabilities of temperatures at or below freezing by over the following days. Areas along and north of 94, primarily in the Chimney region have a 50-80% chance of sub-freezing lows Thursday morning and that drops to less than 30% for Friday morning. Additional headlines may be needed for portions of the area these days.

Thursday - Friday: Warming with a Low Chance of Showers

As an upper low spins across Ontario and the Hudson Bay, weak lobes of shortwave energy are expected to round the western flank of the trough and move overhead by late week. Along with increased theta-e advection into the region, this will allow for some diurnally driven showers to form, especially east of the Mississippi, where upper forcing will be a bit better. The main limiting factor will be the lack of moisture return ahead of this with persistent west/northwest low level flow keeping things fairly dry. 05.00 LREF grand ensemble (EC, GEFS, GEPS) probabilities for measurable precipitation Thursday afternoon peak around 40-50 percent with 20 percent for Friday. Will leave the NBM PoPs as they are for now in the 15-30 percent range both days as there is still plenty of spatial uncertainty with the chances for showers. Temperatures will finally start to warm by late week as the dome of cold air aloft finally meanders east, allowing for temperatures to climb back into the 60s.

The Weekend: Warmer to Start, More Rain Chances

As the aforementioned dome of cold air finally exits the region, 850 mb thermal ridging will start to move into the Upper Midwest by the weekend. Low level warm air advection looks meager overall but should still be enough to help temperatures reach into the upper 60s to lower 70s by Saturday afternoon, especially across Northeast Iowa. A cold front is then expected to drop down into the region late Saturday into Sunday, bringing the best chances for rain with its passage. There are still many details that will need to be ironed out ahead of this with plenty of synoptic uncertainty at this time. Not sure if this is going to provide much relief to the dry conditions as moisture return remains on the low side ahead of this frontal passage but this will be monitored going forward. Post frontal temperatures will be near normal in the 60s for the start of the next work week.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 630 PM CDT Tue May 5 2026

Mainly VFR conditions are forecast for the TAF period outside of a 10-20% chance for MVFR ceilings around midday Wednesday north of an EAU to MFI line. Daytime ceilings elsewhere will otherwise be around 4-6 kft through the midday to afternoon on Wednesday. Winds remain from the northwest around 5 kts overnight, increasing to 10-15G15-20kts for the midday to afternoon on Wednesday.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Frost Advisory from 2 AM to 8 AM CDT Wednesday for WIZ032-041- 053>055-061. Freeze Warning from 2 AM to 8 AM CDT Wednesday for WIZ017-029- 033-034-042>044. MN...Frost Advisory from 2 AM to 8 AM CDT Wednesday for MNZ079- 086>088-094>096. IA...Frost Advisory from 2 AM to 8 AM CDT Wednesday for IAZ008>011- 018-019-029-030.