110 FXUS63 KFSD 091651 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1151 AM CDT Mon Jun 9 2025 .KEY MESSAGES... - Wildfire smoke aloft today may briefly surface again tonight into Tuesday, with some impacts to air quality possible. - Periodic moderate (40-70%) chances for showers and storms Wednesday afternoon through Friday. There is some potential for severe storms and locally heavy rainfall Wednesday and Thursday, but confidence is very low in details at this time. - Breezy and cooler than normal today, but warmer air builds in mid week with highs mainly in the 80s to lower 90s. Late week temperatures becoming more uncertain due to potential impacts from multiple days of convection around the region. && .DISCUSSION... Issued at 410 AM CDT Mon Jun 9 2025 TODAY-TUESDAY: Sharp upper level low spinning slowly east across Minnesota early this morning will gradually move east across the western Great Lakes today, before lifting into Ontario/Quebec on Tuesday. Trailing cold front is currently dropping south across our forecast area. Mostly cloudy skies behind the front will dominate much of today, but the moisture is rather shallow. Expect rain chances to be limited to spotty sprinkles at best, mainly in portions of southwest Minnesota where the cloud layer has a little more depth along with very weak instability. While not as windy as yesterday, expect breezy northwest winds gusting 25 to 30 mph. Low clouds are expected to erode with sunset, but skies could still be hazy due to lingering wildfire smoke aloft. Latest HRRR smoke projections do indicate potential for light concentrations reaching the surface tonight into Tuesday, so some minor impacts to air quality are possible. Otherwise Tuesday will feature a switch to southwest flow and a building thermal ridge which will help pump temperatures into the 80s, with some lower 90s near & west of I-29. WEDNESDAY-THURSDAY NIGHT: A more active pattern returns mid to late week over the northern Plains, however details are still uncertain as run-to-run consistency among the models as been less than ideal. Past several days have seen projections for a northern stream wave to become more dominant and track slightly farther south Tuesday night into Wednesday. This has suppressed the surface front farther south with time, which has impacted not only our temperatures mid-late week (trending not as warm north of I-90), but also the location of favored rainfall chances and potential strong to severe storms. While there are still some differences, the latest models show modest agreement in placing the low level boundary near to south of U.S. Highway 18 by late Wednesday afternoon, pushing farther south Wednesday evening as a wave slides east from the Dakotas into southern Minnesota. Robust instability builds south of the front into our far southern counties late Wednesday, with MUCAPE values 1500-2000+ J/kg. Meanwhile, mid-level westerlies increase north of the front, leading to strengthening deep layer shear >40kt along and north of the boundary. Greatest instability and shear are largely displaced from the other, but there should be a narrow corridor where instability and shear sufficiently overlap to support at least an isolated severe threat late Wednesday afternoon-evening. Location of this has shifted over the past several model cycles, but the latest ensembles focus this area between I-90 and I-80, greatest near the Highway 20 corridor, and SPC has outlined this area in a Day 3 Marginal (Level 1 of 5) risk, with large hail and isolated damaging winds being the primary threats. Will also have to watch for locally heavy rainfall as Wednesday night progresses, as a growing warm cloud depth will support more efficient rain processes and a moderate southwesterly low level jet impinging on the boundary could support some training storms. Again, the exact locations of the above-highlighted features are subject to further changes, so continue to monitor the forecast/outlooks for the latest updates. Uncertainty only grows as we head into Thursday. Wednesday night convection will likely impact the location of boundaries which could focus the potential for additional severe storms and/or heavy rain by later Thursday/Thursday night. Some model solutions lift the 850mb front slightly northward to somewhere in the I-90 to Highway 14 vicinity while others are much more aggressive in pushing the 850mb boundary as far north as I-94. In either case, the primary surface boundary would be displaced south of these locations, which could maintain a potential for additional strong to severe storms and locally heavy rain later Thursday into Thursday night in some portion of our CWA. FRIDAY ONWARD: Yet another wave sliding across the northern Plains will support rain chances into Friday, but the upcoming weekend looks to favor drier conditions with some warming as upper ridging works back into the area. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1148 AM CDT Mon Jun 9 2025 MVFR to IFR stratus will continue to move through the area this afternoon. Further aloft, thick wildfire smoke will linger into the evening. Upstream observations showing 5 to 7SM visibility through central and northern South Dakota from smoke. Models continue to show this smoke settling into the I-29 corridor this evening and persisting through mid-morning Tuesday. Will continue to advertise a 6SM visibility, but may see brief reductions below 5 miles at times. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JH AVIATION...Dux