textproduct: La Crosse

KEY MESSAGES

- Continued cool weather for the remainder of the work week with highs in the 50s and lows in the 30s. Warming back to near average for the weekend and early next week.

- Low spatio-temporal predictability showers develop both this afternoon and again Thursday during the day. Even Friday could see some light showers during the day.

- Best potential for freezing temperatures tonight will be over central Wisconsin and the bog regions, with more widespread frost/freeze concerns for Friday and Saturday mornings.

DISCUSSION

Issued at 110 PM CDT Wed Apr 29 2026

Precipitation Potential into Next Week:

We sit at the base of a broad longwave trough that encompasses much of the northern CONUS, with a pronounced vort swirl noted on water vapor imagery over the Minnesota Arrowhead with a shortwave dropping into central Wisconsin. This extra upper level support allowed our overnight showers to become more vigorous than was predicted at this time yesterday and these showers gradually shift into eastern WI through the afternoon. A brief period of subsidence follows this wave with another undulation wrapping southeastward across the MN/Dakota border. This wave may lead to weak shower development over southwest into south-central Minnesota later this afternoon, which will decay with the loss of solar insolation this evening as they move into southeast Minnesota and northeast Iowa.

Cyclonic flow persists through Friday with daily shortwaves dropping down the upstream flank of the longwave trough, providing enough upper level support and cold air advection to spark diurnal showers across the region. The timing and spatial details of these showers are difficult for the model guidance to capture given their light QPF footprints. Have manually increased the coverage of showers over the blended NBM forecast for Thursday during the day and if the pattern holds, Friday's PoPs will need further increasing.

The start of the weekend is shaping up dry, but the pattern remains relatively active--just in a different way--with several waves cresting an approaching longwave ridge and bringing a chance for showers and storms Sunday through Wednesday. These latter systems could bring a better shot of widespread rainfall, but the ensemble guidance remains heavily spread on when and where any rain occurs.

Frost Freeze Potential through Saturday Morning:

These nearly daily shortwave passages add a wrinkle to the cloud cover, which plays into the low temperature forecast and risk for frost/freeze conditions. With the surface high pressure cell lingering off to the northwest until Friday night, there will also remain a light northwest wind in place overnight on elevated/exposed locations that could keep the surface airmass mixed just enough to prevent frost formation.

Starting with tonight, despite the potential for mid-level clouds over central Wisconsin, the lack of daytime heating and ongoing cold air advection should result in temperatures falling below freezing. The incoming airmass featured lows in the upper 20s to low 30s across Minnesota last night despite periods of clouds and with greater than 75% of the NBM guidance showing lows falling below freezing, confidence was high enough to justify a freeze warning. Closer I-90, there are hints that the cloud cover may thin out and with dewpoints in the upper 20s, the favored bog locales could tank into the upper 20s with there being a 5-10% chance that lows fall into the mid-20s at some spots.

A similar setup looks to be in play for tomorrow night but with temperatures maybe a few degrees cooler, so frost headlines may be expended further southwest than their current footprint. Saturday morning looks to feature the best potential for widespread temperatures near or below freezing as the high finally passes through.

Temperature Trends into Next Week:

Little change in the synoptic airmass occurs until this pattern breaks down Saturday morning, at which point the upper trough shunts slightly more to the east and a Pacific airmass is allowed to infiltrate the region. We remain on the edge of the warmer airmass early next week and while there has been an increase in the number of ensemble members leaning towards higher temperatures, there exists a 10-15 degree spread in the 25-75th percentile high temperature forecast, indicative that small changes to the forecast could quickly alter temperatures.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1231 PM CDT Wed Apr 29 2026

VFR conditions prevail through the TAF period. Breezy northwest winds this afternoon with sustained winds of 15 to 20 mph with gusts of 25 to 30 mph possible. Winds diminish this evening and become light and variable overnight. Northwest winds pick back up again Thursday morning with sustained winds of 10 to 15 mph. Some low to mid level clouds around 5kft to 10kft will continue to be around through the TAF period. A low chance (10 to 20%) of rain showers for central Wisconsin this afternoon and again for southeast Minnesota and northeast Iowa this evening.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Frost Advisory from midnight tonight to 8 AM CDT Thursday for WIZ032-033-041-053>055. Freeze Warning from midnight tonight to 8 AM CDT Thursday for WIZ017-029-034-042>044. MN...Frost Advisory from midnight tonight to 8 AM CDT Thursday for MNZ079. IA...None.