FXUS63 KFSD 210539 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1239 AM CDT Sun Jun 21 2026 .KEY MESSAGES... - Scattered showers with isolated thunderstorms continue tonight mainly along the Missouri River. Storms are expected to gradually become more widespread overnight. While severe weather is not expected, lightning is possible. - Pockets of moderate to heavy rainfall are expected at times overnight and through the first half of Sunday. Flooding is not a concern at this time, but localized ponding is possible. - Beneficial accumulations of 0.50" to 1.00" are expected along the Missouri River Valley with isolated pockets of higher possible across southcentral SD. Flash flooding is not expected. - Below normal temperatures and periodic rain chances continue into the start of next week. Severe weather chances remain low. && .UPDATE... Issued at 909 PM CDT Sat Jun 20 2026 An area of elevated showers and thunderstorms is ongoing from central South Dakota southeast along the Missouri River Valley and into eastern Nebraska and western Iowa. These are expected to expand northward with time, possibly as far as I-90. An area of low to mid- level convergence, WAA, and an increasing LLJ supported by a mid- level passing shortwave will keep showers and thunderstorms in the forecast through the overnight. A second stronger mid to upper-level wave will push into the region from the northwest early Sunday morning. As it does so it will push this first system out and there will be a brief break in showers early morning through about mid- morning. By late morning similar atmospheric conditions as tonight work with increased forcing as the mid to upper wave passes through. Scattered showers and isolated thunderstorms will result, this time mostly along and north of I-90. Weak elevated instability will support a few lightning strikes but severe weather is not anticipated. Some isolated pockets of heavy rain are possible, but risks for flooding remain low. Storms dissipate through the afternoon. In total, beneficial rainfall is expected across much of the region. Up to an inch from central South Dakota along the Missouri River counties. A half to 3/4 of an inch for most of the James River Valley, and a tenth to a quarter of an inch elsewhere. Southwest Minnesota will be the area seeing the lowers rainfall. Highs for Sunday will be cool, in the mid 60s to low 70s. Another round of showers and thunderstorms will be possible Monday night into Tuesday morning. Details are uncertain at this time, but a few stronger storms could be possible. && .DISCUSSION... Issued at 202 PM CDT Sat Jun 20 2026 CURRENTS & TONIGHT: Another seasonable day continues! Taking a look across the area, mostly clear conditions persist this afternoon with most areas sitting in the mid to upper 70s and low 80s. This along with lighter surface winds has made for beautiful conditions weather- wise. Unfortunately, these conditions will be short-lived as cloud cover builds in from southwest to northeast into the evening as our next system approaches. From here, increasing dPVA/frontal forcing along with a weak LLJ (20-35kts) will likely lead to the development of scattered showers with isolated thunderstorms along the Missouri River Valley and portions of southcentral SD initially. Expect coverage to become more widespread overnight as the previously mentioned shortwave zips eastwards across NE just south of the SD/NE boarder leading to a blossoming of development. While severe weather is not expected; the increasing lift and shear will lead to pockets of moderate to heavy rainfall at times from late this evening through Sunday morning. Nonetheless, any rain for the previously mentioned areas will be welcomed especially since this is where the worst conditions of our D2-D3 drought are set up according to the drought monitor. Taking a closer look, don't think any of this developing activity will touch the 2-3" in/hr rates necessary for flash flooding so we should be in good shape overall. Otherwise, expect the scattered rain chances to continue through at least Sunday morning before additional rain chances move in from central SD with our next system. Lastly, expect another mild night with lows expected to gradually decrease into the mid to upper 50s. SUNDAY-TUESDAY: Looking into Sunday, the drearier conditions will persist throughout the day as additional rain chances (40%-80%) develop with the an approaching mid-level low. While severe weather is not expected, ample moisture and strengthening dPVA/frontal forcing should do just enough to keep the scattered showers going during the day with a few additional pockets of moderate rainfall. Nonetheless, should see much of the shower activity begin to taper off during the evening with the loss of diurnal heating and as the previously mentioned system tracks into the northcentral NE. Otherwise, quieter conditions should return by Monday as zonal flow returns aloft. Our next chance for precipitation will likely come by Tuesday as a cold front progresses through the area. While the better forcing will likely be to our north across northeastern SD, we could get just enough instability/shear to get a conditional risk for stronger storms during the afternoon to evening hours. However, there is still some uncertainty. Either way, this would be the next period to watch for any organized convection. Lastly, near to below normal temperatures will continue across the area through Tuesday with highs mainly in the low to upper 70s. WEDNESDAY ONWARDS: Heading into the midweek, quieter conditions should return for Wednesday and Thursday as a surface high tracks through our area. From here, the wave train returns by Friday as quasi-zonal flow helps usher in multiple shortwaves increasing the chances from showers and potentially thunderstorms almost daily (every 24-36 hours) into the following week. While the chances for severe weather are still uncertain at this time, this is another period that will need to be monitored closely moving forward. Lastly, we'll continue to see temperatures build towards more seasonal conditions with highs increasing from the low to mid 70s on Wednesday to the low to mid 80s by Saturday. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1235 AM CDT Sun Jun 21 2026 VFR conditions are beginning to degrade as clouds lower and showers become more numerous across the region. Expect overnight ceilings and visibility to hover between VFR and MVFR and periodically IFR under heavier storms. Severe weather is not anticipated, but some lightning is possible. Scattered showers and isolated thunderstorms continue overnight and into the day Sunday. Storms gradually taper off Sunday late afternoon. Winds are light and easterly with some slight variability. After sunrise winds will become east and increase with gusts of 15-25 kts expected by afternoon. Winds decrease after sunset becoming light and variable near the end of the period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ UPDATE...AJP DISCUSSION...05 AVIATION...AJP