FXUS63 KARX 181820 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 120 PM CDT Mon May 18 2026 .KEY MESSAGES... - The severe weather threat looks lower for tonight. As a result, the Storm Prediction Center has shifted the Slight Risk further south. The northern extent of the Slight Risk now only extends north to Interstate 90 where before it extended as far north as northeast Minnesota. - Patchy to areas of frost possible in north-central and central Wisconsin on Tuesday night and Wednesday night. && .DISCUSSION... Issued at 120 PM CDT Mon May 18 2026 This Afternoon and Tonight The squall line that moved through our area last night has moved south into the Interstate 70 corridor. South of this line, the temperatures are in the lower 80s and dew points ranging from the mid-60s to lower 70s. With rain cooled air north of this boundary, this air mass will remain south of our forecast area for tonight. As a result, we have seen a reduction in the instability available for the storms along the cold front tonight. Surface-based CAPES which looked to be in the 1500 to 2500 J/kg range yesterday are now only up to 750 J/kg. In addition, the stronger 0-3 km and 0-6 km shear remains post frontal. The CAMs are progressively moving the squall line further and further south. Much of the consensus in the CAMs has this squall line moving east across southern Iowa and northern Missouri. Further north, there are more scattered thunderstorms. This has reduced the severe weather threat because there would be less coalescing of the cold pools. Due to this, we reached out to the Storm Prediction Center and was able to get a more southern shift in the Day 1 Slight Risk. It is now south of Interstate 90. There is now a Marginal Risk from Interstate 90 north into Upper Michigan. If there is severe weather, it would occur between 19.03z and 19.07z. The primary threat would be damaging winds. Tuesday A northern stream shortwave trough will move northeast across western and northern Minnesota and northern Wisconsin. This will result in some scattered morning showers. The strong cold air advection in the wake of the cold front will continue into the day. High temperatures for the day will occur around midnight in the mid- and upper 60s. Temperatures during the day will be in the 50s and 60s. Tuesday Night and Wednesday night The combination of mostly clear to partly cloudy skies and light winds will allow temperatures to fall into the 30s and 40s. There could be the potential for even colder temperatures in central and north-central Wisconsin. This could result in some patchy to areas of frost in our traditional cooler areas of central and north- central Wisconsin. Friday into the Weekend A northern stream shortwave will move slowly east through the region. As this occurs, there will be periodic showers and storms. Like yesterday, both the 0-3 and 0-6 km shear remain less than 30 knots. As a result, the probabilities for organized severe weather look low. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1257 PM CDT Mon May 18 2026 VFR to MVFR conditions currently present across the region with south to southwest winds at or below 12 kts. Most locations currently seeing MVFR CIGs in Southeast Minnesota and Northeast Iowa will likely not see improvement through the afternoon as the stratus deck should persist. Another round of showers and storms is expected to move in from the west/southwest this evening, with impacts at the terminals beginning between 01-03Z tonight. This line will gradually move east with lingering showers continuing into the early morning hours. Widespread IFR CIGs are expected to build in behind the showers for tomorrow morning before gradually lifting to MVFR late in the period. VFR conditions are not expected to return until after 18Z tomorrow. Winds behind the showers will turn to the northwest and pick up to between 10-20 kts with gusts in the 20-30 kt range by late morning. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Boyne AVIATION...Barendse