067 FXUS63 KDVN 312309 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 609 PM CDT Sat May 31 2025 .KEY MESSAGES... - Smoke aloft from Canadian wildfires will continue to stream southward through the weekend. Some of the smoke could mix down to the surface and lead to reduced air quality at times. - Active pattern returns Tuesday through Thursday next week, bringing higher chances for widespread showers and thunderstorms. Some storms could become strong to severe on Tuesday. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 217 PM CDT Sat May 31 2025 The main story for the weekend continues to be the lingering smoke aloft from Canadian wildfires. This is being sent southward on northerly flow aloft as we remain on the western side of a deep longwave trough that will loiter over the northeastern CONUS through Sunday night. The HRRR`s Vertically-Integrated Smoke output depicts the smoke just continuing to stream southward today and Sunday, so expect to see hazy skies across the area. Vertical cross sections from the HRRR near our area continue to show the smoke around the 850-700 mb layer, so if the boundary layer can mix that deeply, which it might be able to do today and Sunday, then some of the smoke could mix down to the surface. There continues to be some differences among the HRRR and RAP smoke models on the exact concentration of surface smoke, with the HRRR more aggressive than the RAP, but both indicate at least a small degree of smoke able to reach the surface, which could lead to reduced air quality. Meanwhile, a backdoor cold front has made its way into the region this afternoon from the northeast, which is evident by a wind-shift line, with flow from the northeast over our northeastern CWA. So far, no showers have developed along the boundary, but SBCAPE of 500- 1000 J/kg per the 31.12z HREF ensemble suggests at least modest instability to generate some showers. However, CAMs are still in disagreement on if anything will develop this afternoon and evening, so we have maintained very low PoPs (<20%) for this time frame. Conditions will remain dry on Sunday as an area of high pressure dominates the region, with temperatures continuing to increase, with highs in the lower to middle 80s (warmest to the west). && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 217 PM CDT Sat May 31 2025 The long-term forecast period starts off on a dry and quiet note Monday, thanks to an upper-level ridge over the Plains region sustaining a dry air mass in place. Northerly flow aloft does appear to continue into Monday, so we might still be seeing some hazy skies from the wildfire smoke. Otherwise, the main story for Monday will be even hotter temperatures as 850 mb temperatures per the latest EC and GEFS ensembles increase to between 15-18 degrees C, which is around the 90th percentile per the SPC sounding climatology. The latest ECMWF EFI for high temperatures on Monday is actually showing a larger footprint for values between 0.7 to 0.9 than previous runs, even with a few isolated spots exceeding 0.9. This suggests a pretty strong signal for very warm conditions Monday, with the latest NBM high temperatures for Monday warming to the upper 80s to lower 90s across the area. For Tuesday through Thursday, a more active pattern is expected as an upper-level trough and attendant cold front approaches the region. Abundant moisture from the Gulf should advect higher PWAT values around 1.7 to 2.0 inches per the GEFS ensemble plumes by Tuesday afternoon. This first trough should phase in with a southern stream trough coming from the southwestern CONUS, arriving on Thursday. Combined, these two waves will result in a prolonged period of rainfall chances Tuesday through Thursday (though not a complete washout), with a soaking rainfall expected across the area. Looking at a 72-hr period from Tuesday through Thursday, NBM exceedance probabilities of one inch or more of total rainfall is between 50 to 80 percent and between 20 to 40 percent for two inches or more. It`s still a little early to assess specific details for the severe weather potential, which will depend on the timing of the cold front Tuesday. With that said, machine learning guidance continues to highlight the area with lower-end severe weather probabilities (~15%) on Tuesday and SPC has maintained a Day 4 Slight Risk (level 2 of 5) over nearly the entire forecast area. Expect some adjustments to these coverage details as we get closer to the event as new models become available. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 609 PM CDT Sat May 31 2025 A southwestward moving front (what we refer to as a "backdoor cold front" given its northeast arrival direction) will continue to slowly moving southwest through this evening, allowing for winds at all TAF sites to turn east-northeast. Speeds should be below 10 kt by 02Z and stay as such through Sunday, with at times a variable direction. Smoke aloft from Canadian wildfires will continue to be present, some at times mixing down to below 3,000 ft, causing patches of light haze (for instance, CID indicating 6SM with smoke/haze as of 23Z). This may result in MVFR surface visibility and some restriction in slantwise visibility for aviators this evening. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Schultz LONG TERM...Schultz/Uttech AVIATION...Friedlein