textproduct: Aberdeen

KEY MESSAGES

- Heavy rain is expected beginning this evening over and continuing through Friday evening. The highest accumulations are expected over south central and eastern South Dakota. The probability to see two inches of rain or more reaches 40-60% over east central and south central South Dakota (decreasing elsewhere as you move north and west).

- There is a Slight Risk (level 2 of 4) for excessive rainfall leading to flooding across across the forecast area tonight into Friday. The heaviest rainfall is expected overnight tonight through early Friday morning.

- Near-normal temperatures continue today, with highs in the low to mid 70s across much of the forecast area. Friday and through the weekend will have slightly cooler temperatures, with highs generally in the low 60s to low 70s.

UPDATE

Issued at 905 PM CDT Thu Sep 17 2026

Rain showers are moving northeast across central SD, pretty much on schedule with the forecast PoPs, although slight adjustments were had. Will continue to see the rain that's currently across Nebraska start to move northeast into SD later tonight, with rain overspreading much of the area after midnight and towards 12Z Friday morning.

DISCUSSION

Issued at 148 PM CDT Thu Sep 17 2026

A weak and fairly small upper-level ridge will be sitting over SD this afternoon through the weekend. This ridge, as well as winds from the east and southeast aloft and at the surface will help to move warm and moist air in over SD. This will create a saturated atmospheric environment over central and northeastern SD through the remainder of today and into Friday. PWAT values across central and northeastern SD will be around 1.75 inches, which is above the 90th percentile and the maximum value for this time of the year. This shows how much moisture there is over central and northeastern SD. A low pressure system is moving out of Colorado today and will move over southern SD tonight, into this moist environment. Precipitation along the northern and western side of the low will move into central SD this evening and then over northeastern SD and west central MN tonight. There is a little bit of instability over southern SD moving in with this system this evening and overnight. This could help a few storms to develop and dump a lot of rain in portions of south central SD and a heavier band of precipitation to develop over east central SD late tonight into Friday morning.

Models have been fairly consistent with the location of a heavy band of precipitation, with the heaviest rainfall occurring over south central SD, in a line from around Vivian to Miller and Redfield, late this evening and overnight. Additionally, this band of heavy rainfall will move over east central SD between Watertown and Sioux Falls tonight into Friday morning. There is currently a 40-60% chance of areas along this line to receive 2 inches of rainfall or more. There is a bit more uncertainty about the northern edge of this line of precipitation and how far north the chances for 1 inch or more of rainfall will be. Models show a 40-60% chance for an inch or more of rain in a line from Eagle Butte to Leola and in areas to the southeast until it runs into the line of heaviest precipitation mentions before, as this line has 70-90% chance. The saturated atmosphere will help to get these rainfall totals but the strength and timing of the band of precipitation will also contribute. With the instability over south central SD and the ability for convection to develop, the rain will likely be heavier for a shorter period of time over this area. East central SD on the other hand will have the precipitation around for a much longer time, leading to higher rainfall amounts. There is a slight risk for excessive rainfall from this system over most of central and northeastern SD tonight into Friday. While the ground should be able to take in a lot of the water, depending on how fast it comes down and in areas that get an abundant amount of rain, there could be some impacts in low lying and poor drainage areas as well as some localized areas of flooding. Additionally, there will be minor impacts to rivers and streams from the potential runoff of the rainfall.

After Friday, there will be a couple of shortwaves that move over central and northeastern SD this weekend. This will lead to some more scattered rain showers moving through occasionally during the weekend. There will be some cooler temperatures moving in with the low pressure system starting Friday into the weekend. Temperatures at the surface will be around to slightly below normal, with highs getting into the low 60s to low 70s.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 635 PM CDT Thu Sep 17 2026

Terminals KABR,KATY,KPIR,KMBG

Showers will move into the region tonight and persist through the first half of Friday, ending from west to east across the region. +SHRA is possible at times, with MVFR or even IFR VSBY in BR as well. CIGs will gradually lower tonight, forecast to eventually become IFR for most areas. These lower CIGs will persist through the day Friday, perhaps improving slightly to MVFR later in the afternoon.

ABR WATCHES/WARNINGS/ADVISORIES

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