401 FXUS63 KFSD 110347 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1047 PM CDT Tue Jun 10 2025 .KEY MESSAGES... - Morning showers and isolated thunderstorm Wednesday give way to increased risks for thunderstorms south of I-90 Wednesday between 3pm and 10pm. Conditional risks for severe weather with large hail (1.5") and isolated strong wind pockets (60-70 mph). - Thunderstorm risks continue into Thursday morning, slowly shifting northward. Persistent marginal hail risks along with some potential for locally heavy rainfall are expected. Exact locations remain uncertain, though favor areas along and north of I-90 in to SW Minnesota. - Forecast has trended more unsettled for Thursday with warmer temperatures and risks for isolated to scattered severe storms in the afternoon/evening. - Temperatures rise through the upcoming weekend, bringing additional thunderstorm risks by Sunday and into next week. Monitor for strong storm potential. && .DISCUSSION... Issued at 227 PM CDT Tue Jun 10 2025 THIS AFTERNOON: Hot and dry conditions continue to build into the Tri-state area as surface winds turn west to southwesterly. High temperatures are likely to top the 90 degree mark along and west of I- 29. Smoke aloft continues to remain thin, and is not having any impact on temperatures given the degree of mixing. TONIGHT: Rather messy westerly mid-lvl flow begins tonight, with the first of many subtle vorticity maxima exiting the Rockies and moving into the Dakotas later tonight. While low-mid lvl moisture is considerably lacking tonight, a 30 to 35 knot southerly LLJ will begin to transport moisture into South Dakota overnight. The combination of mid-lvl dPVA and convergence on the LLJ should isolated to scattered high based showers and isolated thunderstorms stretching west to east across the state (mainly along or north of I- 90) through the night. Meanwhile a surface front already sinking into north central SD this afternoon, will continue to push southeast overnight reaching the Highway 20 corridor by daybreak Wednesday. WEDNESDAY: The aforementioned front will become a focal point for convection later Wednesday afternoon and evening. Meaningful surface moisture (dewpoints higher than 60F) currently over Oklahoma, will begin to transport northward overnight, reaching this boundary and seeping slightly north of the boundary through Wednesday morning. CAMS all fairly confident on a mid-lvl impulse arriving into eastern SODAK by mid-afternoon, which when combined with the arrival of convective temps, should be enough to spark isolated to scattered convection within a narrow corridor of 1800- 2500 J/KG MLCAPE. With stronger westerly residing north of I-90, the primed area for convection will be on the southern edge of stronger effective shear. Nevertheless 30 to 35 knots of shear may be enough to promote a few multicell clusters to even a storm or two with supercellular characteristics moving east to northeast. The prime hazards will be 1.5-1.75" hail, with lingering mid-lvl dry air suggesting pockets of strong wind gusts in the immediate vicinity of the front. Overall tornado parameters remain low near Highway 20, however if a storm would happen to cross north over the boundary, stretching could be enough to produce a brief weak tornado. If storm coverage projections increase, then overall severe risk levels may also increase. WEDNESDAY NIGHT: Storms should use up MUCAPE fairly quickly in the evening, with the greater severe weather risk diminishing by 9pm. However, then we`ll watch for the northward retreat of the low-lvl front and increase of the LLJ after dark. Signals in model guidance continue to suggest that elevated convection will begin to increase in coverage late in the evening, though uncertainty on if this area will be south or north of I-90 continues. The rapid influx of moisture Wednesday night (PWATS AOA 170% of normal), combined with modest LLJ convergence on the 850 boundary, lingering 1000-1200 J/KG MUCAPE, and slightly parallel storm motion along the boundary would promote both a marginal hail risk but moreso a heavy rain risk. HREF LPMM suggest potential for 2-4" rain totals in very localized pockets. Currently focused highest PoPs near or north of I-90, with focus for heaviest rain in SW Minnesota. THURSDAY: A stronger mid-lvl trough ejects out of the Rockies early Thursday. Model guidance remains split on just how far north the 850 and surface front will retreat in the morning, with some guidance pushing the front all the way to northern SODAK, and others holding it closer to I-90. This may have a significant impact on the forecast overall with southern solutions locking in more persistent moderate rain through the day and cooler overall temperatures. Northern solutions unlock a stronger warm sector, keep most of Thursday dry, and bring a much greater risks for severe storms to areas west of the James River and along the Buffalo Ridge in the afternoon. The ECMWF and it`s ensembles remain further south with the GFS/CMC ensembles both further north with the elevated front. Regardless of solution, available moisture remains strongly elevated, and any convection should produce high rainfall rates. Greatest excessive rainfall risks are likely to remain north of I- 90. FRIDAY-SATURDAY: Troughing should move east of the area on Friday, with a slight cooldown during the daytime hours and a northerly wind. Ridging moving back into the Plains for Saturday, along with high pressure over the Great Lakes, will keep temperatures near seasonal normals Saturday. SUNDAY-MONDAY: Quite a bit of uncertainty remains in the forecast for the end of the weekend and start of next week, though guidance continues to support an overall increase in the regional severe weather risks. Increasing mid-lvl ridging through the Central Plains will begin on Sunday, allowing one or more subtle waves to cross the ridge. Given moisture return, this might be a favorable MCS setup for the Dakotas, along with above normal temperatures. It`s also possible to see some elevated convection on the nose of the moisture return Sunday morning. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1047 PM CDT Tue Jun 10 2025 VFR conditions begin the TAF period. A cold front continues to push southwards through the area late this evening. Winds ahead of the front remain out of the southwest while winds behind the front are out of the north. Weak showers have developed north of highway-14 which will persist through the overnight hours. A few hours of low level wind shear (LLWS) are expected along and south of I-90 as well. Winds will turn easterly for the daylight hours tomorrow with gusts up to 15-25 knots expected. A second round of showers and thunderstorms is possible mainly east of the James River during the late morning and afternoon hours. Tough to say exactly where storms will initiate and track so did include PROB30 groups for -TSRA in KFSD and KSUX`s TAFs. Some surface smoke is also possible throughout the day tomorrow as well. Chances for showers and storms will finish out the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Dux AVIATION...Meyers