textproduct: La Crosse

KEY MESSAGES

- Dry with seasonable temperatures Today and Monday with highs in the upper 70s to lower 80s. Temperatures will likely remain near to slightly below average for this week.

- Chances (30-80%) for showers and storms return for Tuesday and Wednesday. There is some potential (10-30%) for rainfall amounts over 1" in northeast Iowa and southwest Wisconsin during this timeframe.

DISCUSSION

Issued at 130 PM CDT Sun Aug 2 2026

Rest of Today - Monday: Drier & Seasonable

Upper-level ridging and surface high pressure will be the name of the game for the rest of today and Monday as cloud cover this morning will continue to clear, resulting in mostly sunny conditions. Overall, high temperatures will generally remain in the upper 70s to lower 80s today with a slight increase in high temperatures for Monday as southerly surface flow develops into the region.

Tuesday - Wednesday: Shower and Storm Chances Return

As we head into Tuesday, the overall synoptic pattern changes slightly as an upper-level shortwave trough pushes north of the region with an attending surface boundary translating through the region. Consequently, measurable precipitation chances increase (50- 90%) in the grand ensemble (GEFS/EC/Canadian ensemble) during this period. Overall this setup does not look overly conducive for severe weather due to the timing of the boundary and minimal instability (only around 500-750 J/kg of MUCAPE in the GFS) present during this period. Although, some elongation in hodographs during this timeframe does suggest somewhat favorable shear profiles. In any case, fairly respectable warm cloud depths over 4km and precipitable waters approaching 2 inches would suggest a fairly favorable environment for heavy rainfall. As a result, have noticed a shift of tails of 0 across portions of northeast Iowa and southwest Wisconsin in the EC Extreme Forecast Index. This is being generated in part due to some probabilities (10-30%) of over an inch of rainfall present in the grand ensemble (GEFS/EC/Canadian ensemble). Some of the highest members in the 90th to 95th percentile grand ensemble (GEFS/EC/Canadian ensemble) would suggest amounts in the 2-3" range cannot be ruled out during this period south of the MN state line. So while the threat for severe potential is quite low confidence during this period, will have to watch to see if we can overachieve on rainfall amounts.

In any case, with the precipitation chances, a frontal passage and zonal flow aloft during this period, temperatures will likely remain on the cooler side of normal for this time of year with median high temperatures in the NBM remaining generally in the 70s to lower 80s for Tuesday and Wednesday. Given that much of the local area will be on the cool side of the frontal passage come Wednesday, would not be overly surprising for much of the local area to struggle to reach 80 degrees.

Thursday - Saturday: Staying Seasonable with Shower and Storm Chances

Temperatures will begin to warm slightly again as surface high pressure behind the aforementioned frontal passage will aid in warming surface temperatures. However, given zonal to northwesterly flow aloft late this week, would not expect temperatures to recover all that much with the NBM keeping temperatures near normal. By Friday and Saturday, predictability in the middle and upper-level flow pattern becomes lower as the synoptic pattern favors zonal to northwesterly flow with embedded shortwave perturbations. As a result, thinking there remains some chances for showers and storms at this point in the forecast period, however confidence is very low in details at this juncture as the location of the thermal ridge, which may promote capping aloft, will need to be resolved as well. Consequently, feel the low precipitation chances (10-40%) in the NBM for Friday and Saturday are appropriate at this juncture.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 623 PM CDT Sun Aug 2 2026

VFR conditions currently present across the region. Conditions overnight will be favorable for the creation of valley fog along the Wisconsin and Kickapoo river valleys and potentially portions of the Mississippi River Valley, especially south of KLSE. Forecast light wind layers are expected to be much deeper south of the I-90 corridor so current thinking is that most of the fog formation will be south of this area, especially in the river valleys. There is varying guidance in if the light wind layer will be sufficient for valley fog formation up near KLSE so have continued with the scattered cloud deck and MVFR visibilities from previous packages as this seems most reasonable at this time. If observations and guidance latch more firmly onto a deep light wind layer further north towards LSE, lower visibilities and CIGs may be needed in future updates. Valley fog should burn off by mid morning with conditions returning to VFR. Light and variable winds overnight will pick up through the morning out of the south with some gusts to around 20-25 kts at KRST by the afternoon.

ARX WATCHES/WARNINGS/ADVISORIES

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