FXUS63 KARX 041747 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1247 PM CDT Tue Aug 4 2026 .KEY MESSAGES... - Periodic showers and maybe a rumble of thunder south of I-90 this afternoon and tonight. Overall rainfall amounts should be less than 1/4", with some higher pockets of rain along and south of Highway 18. - Seasonable temperatures throughout the week with highs ranging from the 70s to middle 80s. Temperatures trend warmer this weekend with highs in the 80s to near 90. - Additional shower and storms chances (15-50%) this weekend. && .DISCUSSION... Issued at 930 AM CDT Tue Aug 4 2026 This Afternoon - Wednesday Morning: Periodic Rain and Storms The line of showers and storms along a cold front that moved out of central MN early this morning faded by 9am as the attendant upper wave lifted into SW Ontario. The upcoming rain focus shifts to mainly south of I-90 for this afternoon and tonight as the lower tropospheric baroclinic zone/theta-e axis sags into Iowa and far southern Wisconsin (with convergence strongest in Iowa) and the right-rear quadrant of the upper level jet arrives. Upstream radar trends over Nebraska and western Iowa continue to support that the highest rainfall amounts will be south of the forecast area, with lighter stratiform precipitation possibly advecting as far north as I-90 as we go through the afternoon and overnight. Latest HRRR runs support observational trends and take much of the heavier precipitation closer to I-80 late tonight. Could still pick up a quick 0.5-0.75 inches of rain in pockets along and south of Highway 18 before Wednesday morning given the ample deep moisture present, but otherwise the impacts from this rain look to be minimal. Thursday - Friday: Seasonable and Mostly Dry By Thursday, surface high pressure builds in, giving the area a break from any precipitation chances. On Friday another shortwave trough comes down into the Upper Midwest and while most of the day appears to be dry, there is increased precipitation chances (10 to 30%), however with increased southwest flow in the low levels, there is lower confidence on any surface forcing that would allow precipitation to reach the ground. With the southwest flow, temperatures will also increase a little, more towards the upper 70s to upper 80s. This Weekend: Increasing Warmth with Additional Storm Chances By the time the weekend rolls around, zonal to northwesterly flow establishes itself into the region with continued southwesterly surface flow. Consequently, temperatures are expected to steadily warm through the weekend with the grand ensemble (GEFS/EC/Canadian ensemble) inter-quartile spread ranging from the middle 80s to near 90F by Sunday for high temperatures across the region. With the zonal to northwesterly flow in place, the key question that will need to be monitored for over the weekend is how far northeast does the ridge situated west of the local area build. Currently, there are some respectable probabilities (20-40%) for 1000 J/kg of SBCAPE and 30 kts of shear, so there is certainly some potential for severe weather when also considering AI guidance (CSU/Pangu/FengWu) does paint some probabilities (5-15%) as well. That being said, it will be highly contingent on how quickly the ridge builds in, should it progress into the region faster, this would decrease any convective potential. Regardless, thinking the low to medium-end precipitation probabilities (20-50%) in the NBM for this weekend seem appropriate given the uncertainty of how this weekend may evolve. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1246 PM CDT Tue Aug 4 2026 Periods of showers and perhaps some rumbles of thunder are expected this afternoon and overnight which will result in MVFR ceilings and visibilities at times. Showers and the associated impacts will primarily remain south of I-90, though some model solutions continue to suggest low probabilities (25-35%) for SHRA at the TAF sites generally between 00z-06z, so have continued with PROB30 groups at both locations. Overnight, low level saturation associated with the showers may lead to IFR ceilings for areas along/south of Highway 18 as suggested by the 04.12z HREF/REFS which depict 30-50% probabilities for ceiling heights less than 1kft. Showers shift eastward Wednesday morning while skies slowly scatter out west to east throughout the day. Light northwest winds continue throughout the TAF period. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Cecava/Naylor/Skow AVIATION...Falkinham