textproduct: Aberdeen

KEY MESSAGES

- Strong southeast winds 25-35 mph, gusting 40-50 mph over central South Dakota will diminish this evening.

- Western U.S. wildfire smoke (aloft) will overspread the region tonight into Sunday morning; potentially sticking around for several days while the steering flow winds are out of the southwest.

- There is Enhanced (3 of 5) to Slight (2 of 5) to Marginal Risk (1of 5) for severe weather tonight, mainly throughout and west of the Missouri River valley region. Confidence is low on storm development due to the mid-level thermal capping inversion in place. Convection that does develop/move across central/north central South Dakota tonight could have large hail of up to 2 inches in diameter and wind gusts of 60 to 70 mph. A tornado or two cannot be ruled out, particularly over western Corson/Dewey Counties.

- There is Slight (2 of 5) to Marginal Risk (1 of 5) for severe weather Sunday across the forecast area. Again, confidence is low for storm development during the day, but once we move into the evening and overnight hours, severe storms will be possible. Main hazards are large hail up to 2 inches in diameter and wind gusts of 60 mph.

- Above normal temperatures for Sunday and into next week. Temperatures are forecast into the 90s and dewpoints well into the 60s. This will push heat index values into the mid to upper 90s, with increased risk for heat related illnesses.

DISCUSSION

Issued at 137 PM CDT Sat Jun 27 2026

At 1 PM CDT, skies are mix of sun and clouds. There are a handful of showers/weak thunderstorms around the forecast area early this afternoon, due primarily to weak diffluent flow aloft and adequate mid-level moisture/steep lapse rates. Temperatures are warming through the 70s, on their way to highs in the 80s. Winds are southeast around 10 to 25 mph with gusts 30 to 40 mph throughout and east of the James River valley region. West of said region, southeast winds are stronger, 25 to 35 mph with gusts 40 to 50 mph. A wind advisory remains in place through early evening for these strong winds.

In the current southwest flow trajectory (that's expected to persist for nearly the entire forecast period), a plume of (elevated) wildfire smoke stemming from an intermountain west wildfire is progged (HRRR) to stream northeast into the CWA this evening, persisting through Sunday. It could be sticking around all or some portion of the CWA for quite a while (potential impact on temps/heat concerns?), if the upper level steering flow winds are just right to keep this wildfire smoke plume streaming up into this CWA.

The risk for severe weather, enhanced (3 of 5), slight (2 of 5) and marginal (1 of 5), persists this evening through late tonight, especially west of the James River valley region of the CWA. 15+C dewpoint air at 850hpa will be in place, so no lack of instability/moisture for severe weather. Mid-level lapse rates are progged at 7.5+C overnight, and the deep layer shear is progged between 35 and 45 knots. If the warm 700hpa temps (+11C to +13C) over the western/southwestern forecast zones hold, will have to wait for convection that forms over wrn/swrn South Dakota and nwrn/nc Nebraska to move into the western (west river) forecast zones much later this evening. Throw in a nocturnal low level jet and there is the potential, for organization/upscale growth into one or more (bowing) line segments overnight. Initially, hail of 1-2in in diameter are possible with any storms that can punch through the Capping inversion (quite strong on the 18Z KABR RAOB), with perhaps a gradual transition to more of a wind threat late, provided cold pool/shear organization can land in goldi-locks territory.

Reset the playing field for Sunday, and similar severe weather potential is in play, especially as surface trofs/lows/fronts all start making their way east across the CWA from late Sunday afternoon through early Monday morning. The latest SPC Day 2 Convective Outlook has pulled the slight risk all the way back to near Faith, SD, owing perhaps to the location of said surface wind- shift/troffing features heading into Sunday peak heating. Currently, Sunday afternoon/evening deep layer shear/instability is progged to be higher than this afternoon's/tonight's parameters showcase.

The active southwesterly flow pattern aloft appears to be in play throughout the 7-day. Upper level ridging over the upper and mid- Mississippi River valley is progged to ever so slowly begin retrograding back to the west and north, especially during the second half of the period (Wednesday through Saturday), eventually cutting off the active shortwave-train that southwest flow can bring and turning the region into more of a "ring of fire" type of set-up where mid-levels become too capped and most convection occurs/moves north and east around this CWA. This will translate into several days of above normal high temperatures running from the upper 80s to potentially the upper 90s, provided elevated smoke doesn't prohibit insolation. Will continue to monitor the heatrisk output and apparent T values in the forecast rolling into next week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1240 PM CDT Sat Jun 27 2026

Terminals KABR,KATY,KPIR,KMBG

Copious amounts of low level moisture have cigs forming/reforming at or below 3000ft agl (MVFR) at all four terminals now. At some point between 18Z and 00Z this evening, enough mixing may occur to push the cigs up to VFR. But it won't last. Guidance has cigs crashing into IFR/MVFR later this evening/overnight and persisting through mid-day at KABR/KATY. KPIR/KMBG may be able to clear off, or at the very least improve, to VFR prior to 18Z Sunday. Severe thunderstorms (large hail up to 2 inches and gusts in excess of 55 knots) are a concern later this evening/overnight, particularly at KPIR and KMBG between the hours of 02Z and 07Z. If storms organize overnight, KABR could be into some strong convective activity by 06Z tonight.

ABR WATCHES/WARNINGS/ADVISORIES

SD...Wind Advisory until 7 PM CDT /6 PM MDT/ this evening for SDZ003>005-009-010-015>017-033>037-045-048-051. MN...None.