textproduct: Aberdeen

KEY MESSAGES

- Slight Risk for severe weather (2 of 5) focused across far northeast South Dakota and west central Minnesota this afternoon/evening. Marginal Risk for severe weather (1 of 5) includes parts of the northeast and central South Dakota. Main threat is large hail.

- Colder air returns Monday through Wednesday, with high temperatures around 15 to 20 degrees below normal. Temperatures Wednesday morning may drop to near or below freezing, bringing the potential for frost.

UPDATE

Issued at 856 PM CDT Sun May 17 2026

As the cool stable surface layer deepens on north-northwest CAA winds, got one lone (elevated) cell moving northeast into Grant County SD at this time. Maybe some heavy rainfall and pea- sized hail with it presently. Precipitation has been migrating north and east into the far northeast corner of the state over the past several hours. Within a couple of hours, this activity should clear the far northeast corner of the CWA. No changes planned to the tonight period forecast. The potentially coolest area of the CWA overnight looks to be north central South Dakota, while the potentially warmest area looks to be northeast South Dakota into west central Minnesota.

UPDATE Issued at 642 PM CDT Sun May 17 2026

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

DISCUSSION

Issued at 120 PM CDT Sun May 17 2026

After the first round of showers and storms moved through portions of central SD this morning, most of the forecast area has been in between areas of precipitation with the second round now moving into our south/west zones. This is in association with the next upper wave and inverted sfc trough that has poked northward into central sections of SD. The main low pressure center remains to our south across parts of NE/KS and it is progged to shift northeast by late this afternoon into Sioux Falls/Sioux City area. Of the aforementioned area of precip, an area of stronger elevated convection across north central NE at midday is progged to track northeast into SD through the early afternoon. This area of convection appears to be located around a meso low and attendant cold front that is centered and draped north to south toward the parent low across the NE/KS border. RAP guidance shows an instability gradient set up in the vicinity of this convection across northern NE into far south central SD. This guidance progs this gradient to track northeast from Ainsworth, NE toward Mitchell and Huron SD the first part of the afternoon and then on into our far southeast zones around the Watertown area mid to late afternoon.

North of the elevated convection, we see an area of moderate to embedded heavy rain shifting into the Pierre area(I-90 corridor) and points north toward Mobridge. These rains will be just that and not pose any severe threats to central SD through the afternoon. Visible Sat shows extensive cloud cover(mostly stratus) along and west of the James Valley through central SD. Clear to partly cloudy skies have developed across east central and southeast SD which will help to contribute to destabilization and a more favorable environment for strong/severe convection this afternoon. RAP model does prog MLCAPE values of 1000-1500 J/kg across east central SD/west central MN by mid to late afternoon with ample bulk shear values of 45-55 kts. CAM solutions track that elevated convection northeast from south central SD into parts of southeast SD with additional development possible to the north that would affect some of our forecast area such as Miller to Redfield, Clark, Watertown and Ortonville through the course of the afternoon hours. The main concern with any of the stronger convective cells will be large hail and damaging winds with a more isolated risk for a tornado or two and of course locally heavy rainfall.

By late this afternoon and evening, guidance progs this activity and any generic showers and storms located farther north and west to shift eastward into the James Valley and points east. By early to mid evening, most of the this activity is expected to begin to shift east and out of our forecast area into western MN. A break in the precip is then expected tonight into Monday morning before the next round of moisture shifts north and east back into our region for Monday afternoon and Monday night. This will be more strato-form rainfall with no risk for severe weather expected. Increasing northerly breezes and temperatures cooling into the upper 40s to mid 50s is about as best we be able to manage for Monday. By Tuesday morning, most if not all the precip will be gone and we should be left with mostly dry conditions albeit still cool. This cooler than normal air mass will maintain itself across our area Tuesday night into Wednesday. In fact, we should see 2 overnight's worth of frosty or near frosty like temperatures in the 30s. Late Tuesday night into Wednesday morning still looks to be the coldest with forecasted overnight lows in the upper 20s to mid 30s. More guidance has latched onto this idea leading to higher confidence that a good portion of our forecast area will see frost.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 642 PM CDT Sun May 17 2026

Terminals KABR,KATY,KPIR,KMBG

Ongoing showers and embedded thunderstorms (including occasional MVFR/IFR cigs/vsbys in the heaviest downpours) will depart the region this evening. Outside of areas of precipitation, VFR vsbys and VFR/MVFR cigs prevail. MVFR/IFR cigs are forecast to build over the region tonight, spreading from northeast to southwest and eventually getting to the KPIR terminal by sunrise on Monday. Expect north-northwest winds to persist throughout the 24 hour TAF valid period, including gusts to 20 to 25 knots on Monday.

ABR WATCHES/WARNINGS/ADVISORIES

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