textproduct: La Crosse

KEY MESSAGES

- Dry conditions and warm temperatures through Thursday. Daytime highs will reach into the 70s for most while overnight lows fall into the 40s and 50s.

- Showers and storms are very likely (70-90%) Thursday evening into the overnight hours. A few strong to severe storms can't be ruled out.

- Temperatures cool this weekend into the beginning of next week with another round of precipitation possible (30-50%) Sunday afternoon into Monday.

DISCUSSION

Issued at 205 PM CDT Tue Apr 21 2026

Tonight - Thursday: Dry with a Warming Trend

Dry and warmer weather are in store through mid-week as an upper level longwave ridge remains the dominant feature across the central United States. Broad subsidence and a dry atmosphere limit any precipitation and result in adiabatically warming temperatures, further increased by southerly winds returning Wednesday. High temperatures climb into the 70s for most with some locations along/west of the Mississippi River possibly hitting 80F on Wednesday (30-40%) with lows falling into the 40s and 50s.

Thursday - Friday: Showers and Storms

A round of showers and storms is expected late Thursday through early Friday morning associated with the trough spinning off the west coast of the United States today moving onshore, resulting in a deepening surface low over the northern Great Plains on Wednesday. The cold front associated with this low is expected to be the catalyst for these showers and storms with high confidence in precipitation (70-90%). Still some concern for strong/severe storm potential during this period, but this remains the point of greatest uncertainty in this scenario. Given MUCAPE of 1000-1250 J/kg, some more potent updrafts may be able to develop though wind shear remains the biggest limiting factor to stronger storms. The majority of the shear is locked up "downstairs" in the 0-3km layer owing to rather weak flow at 500hPa. While the instability would support a more potent updraft, the lack of stronger deep layer shear will make it difficult for these updrafts to sustain themselves. If the upper jet streak were to move eastward, increasing 0-6km shear would be supportive of stronger storms over our area. All this said, while a strong to severe storm cannot be ruled out at this time with wind being the primary threat, the better environment appears to be west of our area as depicted by the SPC Day 3 Outlook.

Regarding rainfall amounts during this period, the 21.13z NBM mean suggests around 0.5 inches across the region with the interquartile range sitting around 0.3-0.8 inches. However, the mean is likely inflated by a few outlier members (also noted in the 21.06z GEFS/EPS) likely owing to convective enhancement which can be seen in the deterministic guidance (21.06z GFS/ECMWF) as a "stripey" look. Looking to the AIWP guidance, the 21.06z AIFS/AIGEFS are less gung- ho about the higher end amounts, limiting the outliers to around 1 inch. All that said, tend towards the lower end for amounts to and thinking 0.5 inches or less is the favored scenario at this point, but areas where thunderstorms frequent may see amounts around 1 inch.

Friday - Next Week: Cooler, Another Round of Showers

As we head into the weekend and next week, a cooler airmass is ushered into the region behind the cold front that moves through Thursday into Friday. Temperatures fall to near normal, bringing highs down to the upper 50s to low 60s and lows to per the 21.13z NBM mean although there is quite a bit of spread noted in the 21.06z GEFS/EPS. Another 500hPa trough shifts through the United States Sunday into Monday developing another deep surface low and associated frontal system. The 21.00z LREF membership is in good agreement regarding the development of this low, but the clusters depict more variation regarding the finer details primarily regarding the track of the low, as is to be expected at this range. However, the consensus of this surface wave developing and moving through the Upper Midwest brings a 30-50% probability for precipitation to start the new week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1219 PM CDT Tue Apr 21 2026

VFR conditions will prevail through the period. The weak front continues to sink southward and is clear of RST and LSE. Flow behind the front is calm to light and have prevailed the predominant forecast wind direction through the afternoon, which becomes more from the northeast and remains very light through sunrise Wednesday. Some indications fog may develop toward this latter time frame, but is expected to stay south of the forecast terminals. Winds will become from the east-southeast and increase to between 8 to 12 knots over southeast Minnesota to 5 to 10 knots over southwest Wisconsin by the end of the period.

HYDROLOGY

Issued at 205 PM CDT Tue Apr 21 2026

Flooding along the Yellow River at Necedah, WI continues trending downward today with precipitation not expected through Thursday. While still in minor flood stage as of this morning, the river is currently forecast to fall below flood stage by late Wednesday. Rain returns late Thursday into Friday morning but overall amounts are expected to remain in the 0.3-0.8 inch range, locally around 1 inch where storms frequent. This may result in some minor rises on area rivers, but expecting any rises would result in action stage being exceeded at most. Dry conditions return through the weekend allowing any of these rises to quickly work their way downstream.

ARX WATCHES/WARNINGS/ADVISORIES

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