textproduct: Aberdeen

KEY MESSAGES

- Spotty rain showers (30-55%) are possible through the morning, mainly across portions of central SD to the James River. Additional rain (60-90%) and weak thunderstorm expected midday through Thursday morning with the bulk of the rainfall falling this evening and overnight. Chance of rainfall of a quarter inch or more is 50-90% mainly along and east of I29.

- Occasional rain chances continue for the end of the week with the highest chances (50-85%) Friday evening through Saturday morning, east of the Missouri River.

UPDATE

Issued at 932 AM CDT Wed Sep 23 2026

Other than some minor adjustments to the probability of precipitation forecast, the previous forecast remains on track this morning. Expectations are still that scattered rain showers will continue to move into central South Dakota this morning, progressing slowly eastward through this afternoon and tonight. Generally not expecting much more than light rain as these showers move through, although the strongest showers may have a flash of lightning or two.

UPDATE Issued at 622 AM CDT Wed Sep 23 2026

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

DISCUSSION

Issued at 138 AM CDT Wed Sep 23 2026

The bulk of the low to mid level moisture (RAP 1000-500mb RH>70%) is over southern SD through NE. This will continue to surge northward (thanks to a 25-35kt southerly LLJ) interacting with a weak shortwave aloft. Cams indicate this spotty potential for light rain across portions of central SD through the James Valley with pops diminishing by late morning or so as the shortwave continues to exit to the northeast. Cams seem to handle this potential fairly well but there is a difference in intensity/coverage area and how far north these showers could go in the CWA. So low confidence on who will see the rain with NBM highlighting the bulk of this (30-55%) over south central SD and southward of the CWA. So pops may need to be adjusted through the morning.

The main feature is the negative tilted shortwave that will be over MT/WY by 12Z where it will track northeastward through Thursday morning, clipping the northern half of SD in the process, with southwesterly winds. At the surface, winds will continue out of the southeast ahead of its weak surface low moving in over southwestern ND this evening with another weak low developing over western SD. With this forcing, and ongoing LLJ over central SD pumping in moisture, models indicate precip moving in, mainly across north central SD mid/late morning to even the midday. NBM is the most aggressive with the rain moving in closer to 12Z while HREF mean indicates more 15-18Z as ENS a bit slower on the rain timing entering with GEPS being the quickest. So low confidence on exact timing. As the system tracks northeast, and the low level jet eastward (and weakens bit), rain chances also spread a bit eastward. Again HREF mean and CAMS really keep this rain spotty along the WAA side of the system this afternoon through the evening with the bulk staying closer to the axis of the trough over ND. NBM is still aggressive on pops so they may need to be adjusted as well closer to time. Precip chances and coverage area does increase per CAMS/HREF around ~04-06Z (thus increasing confidence) with the bulk of the pops of 50%+ James Valley and eastward with 80%+ along and east of the Coteau as drier air will already be moving in over central SD on the backside of this system. This is in part to an increase in southwesterly winds aloft at 700mb (25-30kts) and the LLJ strengthening again to around 35-40kts pulling in that moisture. During this time PWAT values are forecast to range between 1.25-1.5" east of the Mo River and highest eastern SD/MN which is about 3 standard deviations above climo per NAEFs. EFI does highlight 0.5 to 0.7 Coteau and eastward with a SOT of zero over far SD/ND/MN border meaning most members are near reforecast climatology and not expecting anything too anomalous. Probability of 24hr QPF>0.25", ending 18Z Thursday is 50-90% James Valley and eastward, and highest along and east of the Coteau. Prob of a half inch is 30-65%, again highest Coteau and eastward. A few of the HREF members do show the potential for weak thunderstorms as MUCAPE will be up to 750j/kg. However no severe weather is expected. Any stronger rain shower or storm will lead to the potential of higher QPF. We are also not outlooked on ERO so flooding is not expected. As the system continues into Canada and dry air spreads eastward Thursday morning, pops will continue to diminishes west to east with the last of rain exiting eastern SD/MN by mid to late morning.

Dry conditions are then expected through early Thursday evening. Chances of precip returns Thursday night across the southern CWA with this moisture spreading northward Friday per a south to north tracking shortwave from the central plains. It then combines and gets absorbed by a negative shortwave trough moving in from the southwest (ahead of a large trough sitting over the PacNW). This system will then track northeast across the region through Saturday morning. The highest pops of 70-85% will be Friday evening through Saturday morning, highest James Valley and eastward (thanks to a strengthening southerly LLJ). Pops diminish west to east as the system moves out by late Saturday morning. Could see another few tenths of an inch of rainfall from this. As of now high pressure moves in behind it with dry conditions expected for the rest of Saturday and Sunday. This unsettled weather pattern setup continues with precip chances again early next week.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 622 AM CDT Wed Sep 23 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR cigs will remain a prevalent trend at all terminals through this forecast cycle. Spotty -SHRAs will be possible at KABR through mid morning or so with more numerous -SHRAs/-TSRAs possible later this afternoon into tonight at all TAF sites. IFR cigs and MVFR vsbys will be possible in the more steady, heavier showers or storms. CIGs may begin to show some signs of improvement late in the period across central SD and in particular at KPIR. Expected a stronger southeast wind to persist through the day and into tonight with gusts ranging between 20-30 kts.

ABR WATCHES/WARNINGS/ADVISORIES

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