textproduct: Aberdeen

KEY MESSAGES

- There is a Slight Risk, level 2 of 5, for isolated to scattered severe storms this afternoon and evening along and east of a line from Murdo to Redfield to Sisseton. Main threats are large hail, 1 to 2" in diameter, and wind gusts of 60 to 70 mph. A tornado or two can not be ruled out. Brief heavy rainfall is also possible.

- There is a Marginal Risk, level 1 out 5, for isolated severe storms north of a line from Pierre to Aberdeen. These storms may form in the heat of the afternoon, but may also move through with a wave overnight. Main threats include 1 inch diameter hail and wind gusts of 60 mph. Brief heavy rainfall is also possible.

UPDATE

Issued at 647 PM CDT Mon Aug 17 2026

See below for an aviation forecast discussion for the 00Z TAFs.

DISCUSSION

Issued at 108 PM CDT Mon Aug 17 2026

Two focus areas for storms in the next 24 hours. The west/northwest flow regime remains in place, with a surface trough just east of the Missouri valley. There is one upper wave on the way out on Water Vapor, not really much of an upper level wave during peak heating today (neutral flow), and a second wave that develops in response to increasing flow aloft as a upper trough over Canada deepens. As such, CAMS are pretty inconsistent in coverage and locations for convection during peak heating, with more coverage during the overnight hours wave. During the afternoon, we're looking at around 2 - 2.5k j/kg CAPE between the RAP/NAM/HREF. Out west/central this afternoon, the profiles indicate mid level moisture, deep dry subcloud layers and skinny CAPE with the HRRR showing an inverted-v type profile. West/northwesterly flow translates into long/straight hodographs. Thus, the severe weather threat may be a wind/hail combo out west/central and more of a hail/splitting supercell environment in the east.

Some minor nuance impacts of the environment: Flow out ahead of the surface trough is southwesterly as the surface high continues to migrate southwards. This would trend us slightly warmer and less humid in comparison to NBM typically. The HRRR appears to capture this drying and more stable conditions on the east side of the boundary. Southwesterlies, even if not that strong, also typically results in longer/straighter hodographs in the low levels which we are picking up at KATY in the NAM/RAP. Likewise, 0-1km SRH is limited to 100m2/s2 across western Minnesota, with the Sig Tor parameter at 1 or less. As such, tornado development may be contingent on storm interactions.

The eastern CONUS trough deepens, with a ridge out west intensifying, strengthening northwest flow aloft. As such, temperatures will remain close to what they have been over the last several days which is near normal, with additional subtle waves for Wednesday and late Thursday. That pattern may break down during the weekend.

In regards to smoke impacts, there remains a steady stream of elevated smoke coming in from the Pacific Northwest thanks to this persistent flow aloft. During the day today, most of that is expected to move across North Dakota/northern Minnesota, but will be more directly overhead for Tuesday. Likewise Smoke intensity aloft (how thick and thus how it will impact temperatures) has seen a downward trend in comparison to a week ago. With the trough/frontal passage later today, northerly flow off high pressure is pretty weak and there isn't a lot of fires in the source region of this airmass, so there isn't much of a concern though the HRRR/RAP both have some lower concentrations coming into the west tonight.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 647 PM CDT Mon Aug 17 2026

Terminals KABR,KATY,KPIR,KMBG

Scattered thunderstorms are working over central, north central and northeast South Dakota. Strong thunderstorm wind gusts are the primary severe threat, although hail up to an inch is possible, too. Most of this round of rain should be ended or clear of the TAF sites by 06Z. However, regional radar and very short term guidance suggests there could be an additional round or two of storms working through the forecast area later tonight after sundown. Southwest winds are switching to northwest overnight as well.

ABR WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None.