


Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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897 FXUS63 KARX 151843 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 143 PM CDT Tue Jul 15 2025 .KEY MESSAGES... - Showers and storms impact the region, mainly after midnight tonight through Wednesday evening. - Locally heavy rainfall is the main concern with these storms, through some will bear watching for a severe potential in the early afternoon in SW Wisconsin. - Cooler to end the week with highs more typical of the first day of fall on Thursday, slowly moderating through the weekend and back to average for early next week. && .DISCUSSION... Issued at 140 PM CDT Tue Jul 15 2025 Tonight - Wednesday Evening: Storm Details Despite being less than 24 hours away, questions linger on the coverage and intensity of storms that move through the region later tonight into Wednesday. Storms initiated sooner and farther south that the 15.12Z HREF members predicted in west-central Minnesota, casting doubts on how these models will handle the evolution of storms as we head through the afternoon and evening. Surface-based inhibition is not overly strong this evening across southeast Minnesota and western Wisconsin, so in theory an outflow boundary shooting southeastward from these cells could trigger new development sooner and farther east than forecast. The good news is that the deeper shear lags on the cool side of the surface boundary over northern Minnesota, keeping the risk for organized convection at a minimum. Nevertheless, storms could produce locally heavy rainfall if they manage to hold together. This brings us to Wednesday. All of the 15.12Z HREF members decay the main slug of overnight convection by the time it reaches our forecast area near sunrise. The rate of decay varies among the models, but residual convective debris should be in place during the morning on Wednesday. The surface cold front arrives in southeast Minnesota in the morning with a low riding up the front during the morning, passing through the area during the midday hours and moving into southern Wisconsin during the afternoon. This only provides a narrow window for severe weather before the threat shifts off to the east. However, the presence of the weak surface flow near the low and the wind shift could be a region that sees landspout processes IF we are able to get enough solar insolation and near-surface instability before the flow switches to the northwest. There is higher confidence that locations along the north of I-90 will see periods of heavy rain in the de-facto deformation zone to the north of the surface low. A look at the LPMM progs from the HREF show corridors of 1-2 inches of rain with pockets of 3-4 inches in some of the worst-case scenario members. Probably not enough to result in too many river problems, but poor drainage areas may be susceptible to flooding. The complex as a whole departs quickly Wednesday evening with CAA setting in Wednesday night. Thursday - Friday: Cooler and Drier The end of the work week will be characterized by a period of cooler and drier weather more typical of mid-September as a shot of polar air grazes the region with the passage of a 1020-mb surface high. Overnight lows will be driven by the degree of cloud cover and could fall into the mid-40s (the NBM 10th percentile) Thursday night in favored spots east of the Mississippi if conditions align perfectly. The Weekend into Early Next Week: Moderating, Rain Returns A mostly zonal flow pattern sets up for the weekend and into early next week with multiple weak undulations in the upper flow driving the risk for showers and storms. The surface baroclinic zone is progged to set up somewhere from the Siouxland on east/southeast, which would serve as a corridor for storms to track during the weekend. A number of medium range members are showing one, possibly two MCSs propagating down this boundary Friday night/Saturday morning and again Saturday night into Sunday. The details on the tracks and impacts from these systems will be refined as we approach the event, but they would likely bring moderate to heavy rain if they do manifest themselves. Low predictability risks for showers and storms dot the forecast for the start of next week with little change in the upper level pattern. Where the surface baroclinic zone hangs up each day will be the focus for higher rainfall amounts. While the forecast is covered with 20-30% rain chances, a look at the individual ensemble members shows that these values are simply driven by the wide spread in the location of this boundary and most locales and times should be dry. With the zonal flow, temperatures recover to seasonal values by early next week. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1205 PM CDT Tue Jul 15 2025 VFR conditions are forecast through much of tonight, with MVFR stratus working in from the northwest around sunrise on Wednesday. This stratus overspreads much of the region aside from far southwestern WI during the morning with additional restrictions due to showers and storms possible after 10-12Z in southeast Minnesota, reaching the LSE area towards 15Z. Winds today remain from the SSW at 10-15G15-25kts, decreasing and backing to the E/SE for the morning on Wednesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Skow AVIATION...Skow