textproduct: La Crosse

KEY MESSAGES

- Cool weather continues through Friday with highs in the 50s and lows in the 30s, leading to periods of frost/freeze concern during the overnights. Temperatures warm towards normal this weekend and into next week.

- Isolated to scattered showers are possible this afternoon and again Friday afternoon (10-30%), but overall timing and location predictability is low.

DISCUSSION

Issued at 1150 PM CDT Wed Apr 29 2026

Cool Temperatures then Warming

Cool temperatures linger today and Friday as an upper level low churns over the Great Lakes region. Confidence remains high in these temperatures as very little spread in the 25th-75th percentiles, on the order of 5 degrees or less, is noted within the majority of the ensemble suite. During the overnight hours, the cold air stagnates under clear to mostly clear skies with nearly calm surface winds. This set up favors frost/freeze conditions, which are expected through Saturday morning with the current frost/freeze headlines possibly needing to be expanded into other counties for the coming nights.

As we head into the weekend, temperatures trend warmer as the upper low shifts eastward, allowing warmer air to advect into the region. High temperatures on Saturday reach into the 60s, again with little variability in the 25th-75th percentiles. A bit more uncertainty in exact temperatures comes into play as we head into Sunday and early next week. Looking at the 30.00z AIFS Ens/AIGEFS, the 25th-75th temperature spread begins to increase beyond Saturday, upwards of 10-15 degrees. The important thing to note is that while the exact temperature is uncertain, the overall warming trend is still depicted despite the variation.

Showers This Afternoon and Friday

With the bowling ball of a low sitting atop the Great Lakes region through Friday, sending shortwave trough after shortwave trough into the Upper Mississippi River Valley within the northwest flow and cold air advection regime, isolated to scattered shower development appears reasonable to expect both this afternoon and Friday afternoon. The primary 500hPa shortwave trough this afternoon shifts southeastward through the morning hours, sparking some weak surface cyclogenesis over eastern Iowa and northwestern Illinois this afternoon that eventually lifts slightly northward into Wisconsin. Forcing associated with these features combined with 0-3km lapse rates steepening to 7-8C/km per the 30.03z RAP should provide enough upward motion for some isolated showers during the afternoon, primarily across Wisconsin where the forcing will be maximized. A similar set-up occurs for Friday, albeit without the cyclogenesis, as another shortwave pivots through the Upper Mississippi River Valley with coverage expected to be a bit more expansive as compared to today. Those further north, especially north of I-94, may even see some snowflakes mix in with the rain during the afternoons. RAP/HRRR soundings show the mixed layer reaching into the DGZ while surface temperatures remain near freezing with the possibility to wet-bulb below freezing. The main limiting factor to precipitation both days is low level saturation. These same model soundings depict some dry air below 5kft which may prove challenging for hydrometeors to fall through, dependent on how strong the forcing associated with the showers ultimately ends up being.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1210 AM CDT Thu Apr 30 2026

VFR conditions are expected throughout the TAF period with sct to bkn clouds between 5kft and 10kft. Winds will remain from the north/northwest today but increase during the late morning to around 8-12 kts. Cannot rule out a passing shower (10-15% chance) at KLSE site during the afternoon hours. However given the low probability and unlikelihood this would result in category reductions, have opted not to include a prob30 at this time.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Frost Advisory until 8 AM CDT this morning for WIZ032-033-041- 053>055. Freeze Warning until 8 AM CDT this morning for WIZ017-029-034- 042>044. MN...Frost Advisory until 8 AM CDT this morning for MNZ079. IA...None.