


Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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940 FXUS63 KFSD 262357 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 657 PM CDT Thu Jun 26 2025 .KEY MESSAGES... - Scattered showers/isolated storms will continue to diminish in coverage through this afternoon. Still a low risk for an isolated strong/severe storm in our far southeast counties this afternoon, but greater threat will be east of Highway 71 corridor. - Periodic thunderstorm chances continue Friday evening through the weekend. Some indication that storms could become strong to severe at times. Begin monitoring this time period if you have outdoor plans. - Warming temperatures and increasing humidity this weekend will bring a risk of heat indices above 100F in some areas Saturday afternoon. Otherwise seasonably warm temperatures will prevail much of next week. && .DISCUSSION... Issued at 258 PM CDT Thu Jun 26 2025 TONIGHT-FRIDAY: As the slow-moving wave lifts northeast through the rest of the afternoon, our remaining showers/isolated storms east of I-29 should continue to push east and diminish prior to sunset. Limited mixing with broad cloud cover today, combined with decent rainfall over the past 2-3 days will leave behind abundant boundary layer moisture. Surface high pressure drifts in tonight, providing light winds and a general attempt at clearing behind the departing wave. This could set up a reasonable set-up for some fog development overnight over a broad expanse of the forecast area, though some question as to whether dense fog will develop or not. This would linger just beyond sunrise Friday, but should burn off pretty quickly. FRIDAY NIGHT-SUNDAY NIGHT: A more unsettled quasi-zonal flow pattern sets up for this last weekend of June, with various waves triggering periodic chances for storms from Friday evening into Sunday. Given some dependence on the previous day`s activity, the exact timing/location of storm chances is somewhat uncertain. However, we could be looking at multiple rounds of strong to severe storms during this period. Currently Friday evening looks to be round 1, though some question regarding whether storms coming out of central SD in the early evening will maintain strength as they move east of the James River. 12Z HRRR/FV3 had presented an alternate scenario showing limited early evening activity with a stronger complex diving southeast out of ND late evening into the overnight; however, the 18Z HRRR has backed away from this, instead keeping the stronger ND complex well to our north. Pockets of damaging wind look to be the primary threat with storms that may impact the forecast area Friday evening. How Friday night-early Saturday evolves could play a role in later Saturday activity and too much uncertainty to pinpoint a preferred solution at this point. That said, forecast soundings are much more robust with projected instability with steeper mid-level lapse rates supporting a greater large hail threat, and dry mid levels and sub-cloud layers providing a risk for damaging wind. Main question would be whether storms can maintain some semblance of organization or be more pulsy as deep layer shear is on the weaker side. Transition to a broad mid-upper level trough takes place Sunday, which would drag a cool front southeast into the area. Could see isolated stronger storms develop along this boundary, though its timing is in question with little model agreement at this range. Compared to today, the coming days will see a return of warmer and more humid air, with highs in the 80s most days, briefly pushing into the 90s on Saturday. Combined with dew points in the 70s, this could produce some areas of triple-digit heat indices by Saturday afternoon, so may have to monitor for possible heat headlines. MONDAY-THURSDAY: Early-mid week could see some modest mid-upper level ridging build into the area, but currently not seeing any signs that significant heat will return. Instead, temperatures look to be near to slightly above normal as we head into July next week. Spotty rain chances may accompany any weak waves that move through the area, but confidence is low in pinpointing any timing or location. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 653 PM CDT Thu Jun 26 2025 A mainly MVFR cloud deck is wrapping around a low pressure system exiting off to the east of the area at the start of the period. The western edge of this cloud deck is slowly eroding, and thus some returns to VFR conditions are likely to occur this evening over parts of South Dakota. However; due to light winds and wet grounds tonight, fog is likely to develop starting around 6-8Z and will likely get dense at times heading into daybreak. Visibilities down to 1/4 mile will be possible over parts of South Dakota especially up by KHON, with 1-2 mile visibilities prevailing elsewhere. After the fog fades around 14Z Friday, VFR conditions are expected for the rest of the period. We look to remain dry for most of the day tomorrow, though a line of storms will attempt to enter the area in and around K9V9 towards the very end of the period. Winds will turn light and variable as we head through the evening hours Thursday, not picking up again until the daytime hours Friday. Winds on Friday will be mainly out of the south/southeasterly direction across the area, with gust up to 25 kts, strongest along the Missouri River Valley in central South Dakota and decreasing as you head east across the I-29 corridor. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JH AVIATION...Samet