094 FXUS63 KFSD 010345 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1045 PM CDT Sat May 31 2025 .KEY MESSAGES... - Canadian wildfire smoke continues to filter in through the weekend. Some ground level smoke and reduced air quality continues tonight, with more widespread impacts Sunday. Conditions begin to improve Sunday night. - Thunderstorm risks return Monday afternoon into Monday night. Scattered severe storms are possible along and west of a Tracy to Sioux Falls to Yankton line. Risks include large hail and localized severe wind. && .DISCUSSION... Issued at 251 PM CDT Sat May 31 2025 CURRENTS THROUGH SUNDAY NIGHT: Showers and isolated thunderstorms continue to pivot around the eastern side of the mid/upper level wave moving through south central SD and northern NE - focusing the showers across south central SD into the southern James River Valley. This should exit the area by mid to late this evening. Wildfire smoke aloft and at the surface continues to advect into the area, with visibility near the US Hwy 14 corridor and northward occasionally dropping to 2 miles or less. Those who are sensitive to smoke should limit exposure. Temperatures have warmed into the upper 70s to lower 80s for most locations. Northwesterly wind gusts around 20 to 25 mph this afternoon and evening taper off tonight. Smoky skies continue through Sunday thanks to continued northwesterly flow aloft. Surface smoke begins to diminish from west to east during the afternoon and evening as lower level winds shift westerly with more improvement through the overnight hours. Reduced visibility and air quality are expected. Despite smoky skies, expect warmer temperatures on Sunday with warmer temperatures aloft in the ridge. Highs in the 80s to near 90. Lows tomorrow night in the lower 60s. MONDAY-MONDAY NIGHT: Attention turns to the developing mid/upper level trough in MT and surface low ejecting out of WY during the day on Monday. A mid level wave and upper level jet streak eject out ahead of the main trough during the day Monday. 31.12z guidance has come in fairly similarly timing wise to the 31.00z runs, but there still seems to be 3-6 hour difference between the fastest (Canadian) and slower (GFS/NAM) guidance. Regardless, surface cold front moves into the US Highway 281 corridor by mid afternoon (3-4 PM). Ahead of the front, we`ll see dew points climb into the upper 50s and lower 60s with temps in the 80s to lower 90s with southerly flow. This leads to increased instability at or above 2000 J/kg. Cap should begin to break near the front through the afternoon. Broad synoptic forcing with the 700mb wave and upper level jet streak increases as we head through the evening. However, in spite of the broader forcing moving in, severe risk may be relatively limited in time (3 PM to 10 PM or so) as instability quickly drops off late in the evening. Greatest severe risk remains along and west of a Tracy to Sioux Falls to Yankton line. Highest shear values and lapse rates remain offset from the highest instability. Main threats with strong to severe storms would be hail to 1.5" (ping pong ball) and wind gusts to 65 mph with DCAPE values around 1000 J/kg. Showers and storms continue to move east with the front through the overnight hours, although additional development behind the surface front is possible with continued broad synoptic forcing and the approach of the upper level trough. Rainfall with this front should be efficient with flow parallel to the boundary and robust moisture return. PWAT values at or above 1.5" to near 2" (which is in the top 1% of values compared to climatology). A deep warm cloud layer near or above 10000 ft aids in widespread moderate to heavy rainfall potential. Given 1 hourly FFG ranging from 1.5 to 2.5+ inches in our area - lowest in northwestern IA - widespread flash flooding is not expected. However, heavy rainfall rates could lead to localized issues especially in urban areas. Rainfall amounts into Tuesday morning between 0.75" and 2" expected. Chances of more than an inch remain moderate (40-60%). TUESDAY: Cooler, cloudy, and rainy Tuesday as the mid and upper level trough continue to move east and the surface front pushes through IA. Highs in the 60s to near 70. Breezy northwesterly winds expected. Additional rainfall amounts of a tenth of an inch up to an inch - highest in southwestern MN and northwestern IA. WEDNESDAY ONWARD: Quasi zonal to northwesterly flow develops for mid week into next weekend. Numerous mid/upper level short waves trek through the northern and central Plains which keeps periodic low to moderate (less than 50%) shower and storm chances in the forecast. Severe storms currently look unlikely. Temperatures moderate closer to normal with highs in the mid and upper 70s and lows in the mid 50s. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1045 PM CDT Sat May 31 2025 VFR and MVFR visibilities are expected through this period. Reductions in visibility are the result of thicker plumes of smoke drifting through the region overnight. Light and variable winds overnight will become southwesterly, then southerly after day break. As they do so they will push some of the smoke out of the region and visibility should return to VFR. Though smoke is expected to thin, it will continue impact the region through Sunday. Winds will increase slightly by mid-day with some gusts to 15 kts possible west of the MN/IA/SD border. Strongest gusts are expected over south central South Dakota, where gusts to 20 kts are possible. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...SG AVIATION...AJP