textproduct: La Crosse

KEY MESSAGES

- Below normal temperatures linger across the region today and tonight, with highs in the 50s and lows in the 20s to 30s. Another frost/freeze headline will likely be needed tonight into Saturday morning.

- Temperatures trend warmer and towards normal Saturday into early next week.

- Periodic chances for rain continue into early next week. Isolated showers are possible this afternoon (10-30%) with more widespread rain Sunday morning and again Monday.

DISCUSSION

Issued at 1234 AM CDT Fri May 1 2026

Today - Saturday: Lingering Cool Temps then Warming

Another day of below normal temperatures is in store for the Upper Mississippi River Valley as we sit in the base of a longwave trough/low churning over the Great Lakes. Northwest flow continues ushering cool air into the region from the north with many mid to upper level impulses following suit. The main waves for today come in the form of two subtle 700hPa shortwave troughs that slowly swing southeastward through the day. As these waves move through, low level lapse rates steepen via diurnal mixing which may allow diurnal cumulus and possibly some showers to develop (10-20%) again during the afternoon hours. The main point of uncertainty regarding showers is how dry air depicted in the subcloud layer impacts the precipitation. Tend towards the majority of precipitation falling as virga especially with the recent HRRR/RAP runs coming in drier across our area, so have leaned into the lower probability space. That said, can't rule out some isolated sprinkles/showers given the adequate forcings. Those north of I-94 may even see some snowflakes mix in with showers that are able to develop earlier in the afternoon as temperatures hover just above freezing and the wet-bulb temperature sit at freezing, but this potential decreases as the afternoon wears on.

As we head into tonight, low level ridging, clear to mostly clear skies, and light to calm winds provide a prime set-up for efficient radiational cooling and temperatures plummeting into the 20s and 30s. With these factors in place, another night of frost/freeze conditions are anticipated, the most favorable out of the last few nights. Another night of frost advisories and freeze warnings will likely be needed.

Southerly flow develops on the backside of the ridge Saturday, bringing warmer temperatures northward and pushing highs to around 60 degrees, near normal for this time of year.

Sunday - Early Next Week: Warmer with Periodic Rain Chances

Warmer temperatures linger through the weekend as low level southerly flow remains the dominant influence over our area. Much higher agreement in temperatures this weekend is noted amongst the NWP/AIWP guidance as compared to yesterday, which have brought the 25th-75th percentile spread from 10-15 degrees to around 5 degrees. There are still some cooler outliers in these solutions, but the overall consensus now centers on temperatures topping out in the 60s to around 70 through Monday.

850hPa warm air advection ramps up into Sunday morning on the backside of the low level ridge along with a signal for some weak moisture transport nudging into the area. At the same time, global deterministic models highlight a 700hPa shortwave diving southward atop the low level forcings within the mean northwest flow. Combined with a saturating column depicted in GFS soundings, conditions appear favorable for a round of rain Sunday morning. The 30.12z LREF suggests 30-40% probabilities for measurable rainfall during this period whereas the 30.19z NBM only has 10-20%, likely owing to its low QPF bias.

Confidence in temperatures decreases again after Monday. A higher amplitude 700-500hPa trough looks to swing across the northern United States, dragging a surface cold front through the Upper Midwest during the day Monday. Some variation regarding location and timing is noted between the members of the 30.18z GEFS/EPS and their AI counterparts, leading to temperature spreads on the order of 15 to 20 degrees which are also noted in the 30.19z NBM. Despite the kinks to work out regarding location and timing, most ensemble members depict these features shifting through the area in some capacity. THe 30.12z LREF tends towards broadbrushed 30-60% probabilities while the 30.19z NBM depicts a 20-40% chance for measurable rainfall. Both ensembles highlight central Wisconsin as the most favorable location for precipitation at this point. Temperatures then trend cooler again into the middle of next week in the wake of the cold front.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 541 AM CDT Fri May 1 2026

VFR conditions are highly likely (95%) to prevail over the next 24 hours with the exception being the very low chance of a stray MVFR ceiling. Ceilings should stay above 4kft, mainly in the 5-10 kft range. Winds will be out of the north-northwest today to around 10-15 knots, becoming out of the west very late in the period. No large scale reductions are on the horizon until perhaps Monday.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Frost Advisory until 8 AM CDT this morning for WIZ032-041-054- 061. Freeze Warning until 8 AM CDT this morning for WIZ017-029-033- 034-042>044-053-055. Freeze Warning from midnight tonight to 8 AM CDT Saturday for WIZ017-029-032>034-041>044-053>055-061. MN...Frost Advisory from midnight tonight to 8 AM CDT Saturday for MNZ079-086>088-094>096. Frost Advisory until 8 AM CDT this morning for MNZ079-088-096. IA...Frost Advisory from midnight tonight to 8 AM CDT Saturday for IAZ008>011-018-019-029-030. Frost Advisory until 8 AM CDT this morning for IAZ011.