textproduct: Aberdeen

KEY MESSAGES

- There is a Marginal risk (level 1 out of 5) for severe storms over central and northeastern SD and west central MN today. The primary hazards in the morning and afternoon will be 1 inch in diameter hail and 60 mph wind gusts. Additionally, the threat for a tornado or two over east central SD cannot be ruled out. For the evening and overnight, the primary hazard will be 60 mph wind gusts with small hail also possible.

- Northwest wind 15 to 30 mph and gusts of 25 to 45 mph, low relative humidity, and dry cured fuels may result in fire weather concerns over north central SD on Tuesday.

UPDATE

Issued at 1233 PM CDT Mon Sep 7 2026

See below for an aviation forecast discussion for the 18Z TAFs.

UPDATE Issued at 1036 AM CDT Mon Sep 7 2026

No changes planned to the today period forecast. Periods of rain/embedded thunder to persist off and on throughout the day. Surface through 850hpa analysis reveals low level CAA is over southeast MT/northeast WY, with a cold front positioned along the Dakotas border with MT and WY.

UPDATE Issued at 535 AM CDT Mon Sep 7 2026

Updated for 12Z Aviation Discussion below. Also, did minor tweaks to the PoPs to better align them with the areal coverage of the thunderstorms that have developed in central SD.

DISCUSSION

Issued at 130 AM CDT Mon Sep 7 2026

For today through Tuesday morning, there will be 3 different causes of showers and storm chances from different forcings moving through. There is a Marginal risk (level 1 of 5) for the storms today to become severe, with slightly different hazards from the different causes. For the first cause, an upper-level shortwave moving along the upper-level ridge that continues to sit over SD will help to provide upper-level support for scattered showers and storms early this morning into the afternoon. Similar to the previous mornings, a low level jet will be providing the main support for development as it develops over warm air and moisture advecting into central SD early in the morning, which then shifts over northeastern SD and west central MN later in the morning and into the afternoon. CAPE values during the morning are forecast to be between 1000-2000 J/kg, which will help with the development of elevated clusters of showers and storms in the weakly forced environment. Lapse rates between 5-7 C/km as well as bulk shear values between 30-45kts in the environment could help the storms to become severe. With the elevated nature to the storms, hail up around 1 inch and wind gusts of 60 mph will be possible.

Along the western edge of the moisture advection, there looks to be a weak dry line/outflow that might develop during the afternoon into the evening, which will be the second cause of convection developing. This boundary looks to mainly move through southeastern parts of SD, though portions of south central SD east of the Missouri River and east central SD could be clipped by it. With a strong pressure gradient over eastern SD helping to support the low level jet sticking around into the afternoon hours as well as stronger lapse rates helping to get those winds to the surface, surface winds will be able to gust up around 30-40 mph over areas east of the Missouri River. This will help to create a fair bit of low level shear during the afternoon. While the weakly forced showers and storms talked about will be elevated in nature and not able to access this shear, the weak dryline/outflow moving through in the afternoon and evening will be able to. Because of this, the development of a tornado or two cannot be ruled out in these storm after around 1 pm CDT over southeastern and east central SD. The shear will also help the storms develop hail up around 1 inch and wind gusts of 60 mph.

An upper-level trough will be pushing the upper-level ridge out of SD Monday evening and overnight while also supporting a cold front at the surface moving through Monday afternoon overnight into Tuesday morning. This cold front will be the third cause of convection that could produce showers and storms. While models vary the timing of the front, it is forecast to move into central SD late Monday afternoon/early evening and then move through northeastern SD late evening overnight into Tuesday morning. The other causes of convection will have used up a lot of the instability over southern and northeastern SD through the day which will help to keep showers and storms from developing when the front moves through those areas. However, there will still be around 1000-2000 J/kg of CAPE over northern SD and ND as well as a fair bit of moisture to get some isolated showers and storms to develop over north central SD this evening and far northeastern SD and west central MN overnight. The environment will have weaker lapse rates while also having about 35- 50 kts of bulk shear in the atmosphere to help the storms become severe. Since the storms will be forming along a frontal boundary with a lot of shear, strong winds will be the primary hazard, with gust up around 60 mph possible. There could also be some smaller hail that develops, though it should be less than 1 inch.

After the cold front moves out Tuesday, a high pressure slips in over southwestern SD. This helps a stronger pressure gradient to develop over northern SD and ND, which will create stronger winds aloft that could get to the surface during the afternoon. There is a 30-60% chance that there will be wind gusts greater than 35 mph Tuesday afternoon over north central SD. Additionally, with colder and drier air moving in behind the front, the relative humidity values will be lower. Right now, models are showing humidity values between 20-30% over areas west of the Missouri River. In areas where the strong winds and low humidity values overlap, there will be some fire weather concerns, especially with dry fuels already in those areas. This potential should be watched over the coming model runs as a Red Flag warning might be needed for portions of north central SD. The past few model runs have shifted the stronger winds to the north out of northern SD, and if they continue this trend, then a Red Flag warning might not be needed. With drier air moving in, central and northeastern SD and west central MN will be getting a couple day break from all the weakly forced scattered showers and storms that have been happening the past few days.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1233 PM CDT Mon Sep 7 2026

Terminals KABR,KATY,KPIR,KMBG

There are pockets of sub-VFR low clouds hiding under the convective cirrus shield overhead. The stratus appears to have most recently cleared the KMBG terminal, but is still intermittently impacting the KABR and KATY terminals. Also, a large cluster of thunderstorms (recently clear the KPIR terminal) is moving east-northeast and may impact the KABR and KATY (low confidence) prior to 00Z this evening. Storms may persist at the KATY terminal a bit longer into the evening after 00Z. Also, overnight, low level wind shear potential will exist at the KATY terminal. There is also a cold frontal passage forecast to happen across all four terminals from early this evening through early Tuesday morning. South-southeast winds 10 to 25 mph with gusts up to 45 mph will switch behind the front and become west-northwest, eventually increasing in speed Tuesday morning to 15 to 30 mph with some gusts at times to 45 mph.

So, an overall trend toward VFR flying weather (including a decreasing trend in thunderstorm potential) is expected from west (KPIR/KMBG) to east (KABR/KATY) during the first 12 hours of the TAF valid period, will all TAFs in dry VFR flying weather Tuesday morning on west-northwest winds.

ABR WATCHES/WARNINGS/ADVISORIES

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