textproduct: Aberdeen

KEY MESSAGES

- Red Flag conditions again for portions of central South Dakota with afternoon humidity down around 20% and winds out of the southeast gusting 20 to 35 mph.

- Showers and thunderstorms returning starting Saturday night, continuing through Sunday, with rain persisting into Monday.

- Slight Risk (2 of 5) mostly focused across northeast South Dakota and west central Minnesota Sunday afternoon/evening. Marginal Risk for severe weather (1 of 5) includes parts of the northeast and central South Dakota. Main threats are large hail and a tornado or two.

- Colder air returns Monday and Tuesday, with high temperatures around 15 to 20 degrees below normal. Temperatures Wednesday morning may drop to near or below freezing.

UPDATE

Issued at 617 AM CDT Sat May 16 2026

Updated for the 12Z TAF discussion below.

DISCUSSION

Issued at 210 AM CDT Sat May 16 2026

Mild level warm advection responsible for some light returns on radar and some clouds out in northwest South Dakota, migrating east, however a deeper dive into the environment indicates a deep dry subcloud layer below 10kft with dewpoint depressions about 20C all the way to the surface.

As high pressure to the north migrates east, and a lee low develops out west, return flow increases in strength. Still a very dry airmass in place, with temperatures little changed in comparison to the last few days. As such, despite the shift in wind direction, Red Flag conditions once again for the western portions of the CWA.

CAMS show dry conditions continue through 03Z Sunday after which broad area of weak shower/storm activity lifts into central/north central South Dakota as mid level warm advection increases. The northeast is closer to after 06Z. NAM BUFKIT profiles depict mainly moist adiabatic lapse rates and shallow instability with a stronger thermal gradient in the mid levels across the northeast. 1/2km winds are southeast to northwesterly, so the nose of the low level jet may support more vigorous precipitation across the western Dakotas, something the CAMS may also be hinting at.

That initial round of activity will have lifted all the way into North Dakota by 15Z Sunday with a gap in precipitation before enhancement with the next southwest flow wave, posed along the NE/SD state line at 00Z. Some CAMS do have the area in-between these systems still generating moisture, as well as the NAM/Canadian. As we move from 00-06Z, QPF shifts to along the northeast/southwest oriented inverted trough that extends up into western Minnesota. The GFS has this feature along the SD/MN state line, with the NAM a little farther west.

NBM CAPE mean is around 500j/kg or less Sunday afternoon, and while the NAM has a bit more elevated CAPE (1500j/kg), NAM BUFKIT shows a stable low level airmass across the northeast. That said, strong unidirectional shear within this elevated instability would still support elevated supercells/large hail threat. EC ensembles CAPE tops out at 2k, GEFS up around 3.5k. Bulk shear ensemble mean is around 50kts, and NAM/RRFS hodographs above the stable layer (2km) continues to be generally/mostly straight line with strong southwest mid level flow. Low level southeasterlies in the NAM thus present a better shear profile for tornadogenesis, however the linchpin is daytime heating with those NAM profiles also indicating stable conditions even into Sunday afternoon/evening. When it comes to the cold airmass mid-week, using the 10th percentile, in what would be a worst case scenario, NBM 7am temperatures for Tuesday morning are down around the low 30s across north central South Dakota. With the departing low, surface winds in the NBM are still between 15-25kts, meaning while temperatures will be cooler, its not likely a frost setup. The focus for worst case scenario Wednesday morning is a lot less localized and consists of the entire CWA down into the upper 20s and low 30s. Again, that is worst case. The degree of daytime heating driven cumulus that occurs in the more humid cool airmass during the day Tuesday may also have an impact on the temperatures that night. All that said, deterministic/mean NBM has temperatures low enough to continue to warrant frost mention.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 617 AM CDT Sat May 16 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will continue through the next 24 hours. Non- diurnal wind are expected Saturday evening, with winds gusting 20-30kts by 03Z Sunday. Showers return after 06Z, with the best chance of showers at ATY and PIR. Have kept the mention of thunderstorms out of the forecast due to the low probability, but they may be needed as the time nears.

ABR WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning from 3 PM CDT /2 PM MDT/ this afternoon to 10 PM CDT /9 PM MDT/ this evening for SDZ033>036-045-048-051. MN...None.