239 FXUS63 KFSD 101135 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 635 AM CDT Tue Jun 10 2025 .KEY MESSAGES... - Slight visibility reductions along with minor air quality concerns from wildfire smoke into this morning, and possibly again late tonight into Wednesday morning. - Morning showers Wednesday give way to increased risks for thunderstorms south of I-90 Wednesday afternoon and evening. Marginal (Level 1 of 5) risk for severe weather with large hail and isolated strong wind gusts. - Unsettled pattern with periodic thunderstorm chances continues into the weekend. Only marginal confidence on exact timing and location, but isolated strong to severe storms and locally heavy rain are possible Thursday afternoon/night. - Temperatures rise through the upcoming weekend, bringing additional thunderstorm risks early next week. Monitor for strong storm potential Sunday-Monday. && .DISCUSSION... Issued at 430 AM CDT Tue Jun 10 2025 TODAY-WEDNESDAY MORNING: Building mid-upper level heights today will allow warmer air to expand into the region, with highs this afternoon in the mid 80s to mid 90s. Tonight a weak wave will slide atop the broad upper ridge, dragging a frontal boundary slowly southeast through the area. This boundary will become a focus for high-based showers and perhaps a few storms as we head through tonight and Wednesday morning. WEDNESDAY AFTERNOON-FRIDAY: The boundary continues to push south through Wednesday afternoon and should be a focus for late day thunderstorm development Wednesday. Unfortunately, still not seeing a lot of agreement on the placement of the surface front, though broad consensus looks to be between Highway 18 and 20 in northwest Iowa. As a broad wave arrives from the west, expect to see storms develop along to just north of the surface boundary in the late afternoon, tracking east through the evening. Forecast soundings show the antecedent air mass is still relatively dry in the mid levels, which could support corridors of stronger winds with cold-pool dominant storms. Isolated large hail is also possible, but displacement of the stronger instability south and stronger shear north of the boundary leaves a narrow corridor of support for organized hail-producing storms, perhaps as large as half dollars with the strongest storm cores. Later Wednesday night into Thursday evening could be a repeat of tonight. This would begin with development along the elevated warm front as it lifts back to the north and a weak low level jet impinges on the boundary into Thursday morning, followed by a potential for stronger convection Thursday afternoon/evening as another wave slides into the area. Models begin to show less and less agreement on placement of boundaries, which will ultimately depend on the previous day`s activity. This leads to waning confidence as we move forward in time. However, if there are boundaries in the area later Thursday, they should become the focus for late day development. Similar to Wednesday, stronger instability and shear are not coincident, so again would expect isolated strong to severe storms. One additional concern for later Thursday and especially Thursday night would be a potential for areas of heavy rainfall. Deepening moisture profiles and warm cloud depths will lead to efficient rainfall producing storms, and the main question will be whether successive rounds of showers and storms Wednesday into Thursday night will impact the same locations or be more transient. SATURDAY-MONDAY: Not a lot in the fine detail department to latch onto in this long range period. There is some model consensus that a broad upper ridge will become established from the Desert Southwest into the southern-central Plains early next week, and various shortwaves topping the ridge will bring periodic storm chances to the northern Plains. However, uncertainty in timing and location abounds given lack of model agreement in those finer details. That said, Sunday-Monday will be a period to monitor for severe weather risks if the storm track falls across our forecast area. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 635 AM CDT Tue Jun 10 2025 Areas of MVFR-locally IFR visibility as we start this TAF period, likely a combination of smoke and shallow/valley fog. Any fog will quickly dissipate by 13Z-14Z, but minor visibility restrictions in smoke may linger through midday. Additional light surface smoke may settle southward into the area after sunset tonight, but low confidence in visibility impacts so opted to not include in the TAFs at this time. Locations north of I-90 may also see high-based showers after 11/06Z as a front drops southeast through the area, but again confidence is too low to include as coverage would be rather sparse. Southwesterly winds ahead of the approaching boundary may produce occasional gusts to around 20kt this afternoon, with wind direction shifting to the north and northeast after the front passes tonight. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JH AVIATION...JH