textproduct: Aberdeen

KEY MESSAGES

- Bands of rain will continue this morning across the region, with the exception of far northeastern SD into west central MN. Rain will taper off northwest to southeast through late this afternoon. Rainfall amounts exceeding 0.25" is 40 to 55% along and south of a line from Eagle Butte to Watertown.

- There will be a brief break on Tuesday before spotty chances of rain returns Tuesday night across central South Dakota. Occasional rain chances continue Wednesday through the end of the week with the highest chances (50-80%) Wednesday afternoon through Thursday morning from north central through northeastern SD into western MN.

- Temperatures will remain near to slightly below seasonal averages through Tuesday before climbing above normal toward the middle of the week.

UPDATE

Issued at 638 AM CDT Mon Sep 21 2026

The aviation discussion has been updated for the 12Z TAFS.

UPDATE Issued at 348 AM CDT Mon Sep 21 2026

With heavier bands of rain falling across Spink County and eastward, did up the QPF a bit over this area for higher amounts potentially reaching a half inch through this afternoon.

DISCUSSION

Issued at 123 AM CDT Mon Sep 21 2026

As of 1am the large and wavy ridge continues to our north and beneath this, a persistent and slow moving upper level low is spinning over southern/southwestern SD and northern NE border. This is continuing to bring bands of rain showers to the region with the bulk of the moisture over southeastern to east central SD with more spotty precip over central SD as the bands tracks north and west per counterclockwise flow. Through the morning, this low will continue to track east and southeast along the border (and weaken) with the open wave over ~NE/IA border by 21Z. As this system moves out rain will diminish northwest to southeast (used a blend of NBM/Conshort/ECAM) with the last of the rain exiting east central SD this afternoon. QPF (or additional rain for some) ranges from around a quarter to potentially half of an inch over portions of south central to east central SD with QPF decreasing significantly, to a couple hundredths of an inch to nothing, the further north and northeast in the CWA due to the storm track as well as drier air from a large mid level to surface high that resides over Ontario. With the region on the western to southwestern side of this high, overall dry conditions are expected tonight. Dry weather continues Tuesday, however, weak shortwave energy (under the ongoing ridge) will be over the region which will bring back some clouds to the CWA and slight chances of pops over portions of south central SD in the afternoon. With help from an increasing LLJ (25-35kts), the chance of light rain spreads, as both EC/GEFS does highlight this. NBM indicate spotty coverage of pops of 20-45% across central SD, highest over far south central SD (mainly Lyman/Buffalo counties and southward Tuesday night/early Wednesday.

As the high drifts off towards the east/northeast, a negative tilted shortwave will track northeast (that developed over southern CA/Pacific) and move in over the western Dakotas/MT/WY Wednesday evening and tracking over ND/MN through Thursday morning. There is a bit of a difference between the models on exact track and intensity of this trough at this time. This will bring the return of moisture to the area with models at this point having the precip move in over north central SD Wednesday morning and becoming more widespread across the CWA by Wednesday night (NBM pops 50-80%) with rain ending west to east across the CWA by Thursday afternoon as the shortwave exits the region. Again, timing between models varies a bit on when the last of the rain exit with GEPS being the slowest. Probability of 24hr QPF>0.25", ending 12Z Thursday is 35-65% from north central through northeastern SD/western MN, highest over northern Corson into ND and along and east of the Coteau. With this -PNA pattern setting up for the end of the week, another shortwave moves in for Friday (per southwesterly flow). This feature interacting with southerly flow and pulling in moisture will result in additional rain chances Friday/Saturday. Low confidence in exact setup/track at this time and overall coverage of rain. As of now NBM pops ranges from 20-40% along and east of the Mo River and highest James Valley and eastward.

Our windiest day of the week will be Tuesday afternoon (west of the Mo River of 20-30kts) as the high exits and increasing pressure gradient on the back side of it and east of a lee front. This increased gradient/development of a 30kts LLJ, the gusty winds will spread eastward across the CWA through Wednesday afternoon with NBM gusts between 20-35kts. Ongoing easterly flow at 850mb to surface (and lingering clouds) will keep temps cool again today withs highs in the upper 50s to the lower to mid 60s. Low level winds will be more southeasterly for Tuesday, but with the high still influencing the area, temps will only warm up a few degrees with highs overall in the 60s. South to southwest flow (and high moves out) will lead to temps warming back up to above normal with the warmer air spreading eastward across the CWA for the end of the week with highs in the upper 60s and 70s.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 638 AM CDT Mon Sep 21 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR cigs will be most prevalent at KATY/KPIR terminals through the daytime hours today. KABR/KMBG terminals will see a more prevailing VFR/MVFR ceiling through the day. Light showers will continue to hang around through at least a portion of the morning hours before slowly fading away. KATY/KPIR will hold onto the light shower chances the longest. East to northeast light to moderate winds can be expected today before turning more southeast late in this forecast cycle.

ABR WATCHES/WARNINGS/ADVISORIES

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