textproduct: Bismarck

KEY MESSAGES

- Isolated showers are possible across the south tonight.

- Low to medium chances for showers and thunderstorms mainly west and north central Wednesday evening through Thursday morning. Periodic chances for showers and thunderstorms will be possible Friday through Sunday.

- Medium to high chances for showers and thunderstorms Sunday night through the early portions of next week.

- Expect a warming trend through the end of the week, then cooling somewhat late this weekend into early next week.

DISCUSSION

Issued at 1245 PM CDT Tue Sep 1 2026

We are currently situated under weak High pressure aloft as well as at the surface, between our exiting cyclone that brought us the windy conditions yesterday and another upper level low over the eastern Pacific. A shortwave to our south will spark showers and thunderstorms from south central SD into southern Minnesota later this afternoon through tonight. This activity is forecast to remain well south of the state. However, isolated to scattered showers could slip into far southern ND tonight.

As the eastern Pacific upper low drops south along the British Columbia and Pacific Northwest Coast tonight through Wednesday, the upper level flow transitions to a southwest flow and wave will eject northeastward through the Rockies and into our neck of the woods late Wednesday. This will bring our next chance of showers and thunderstorms. The main wave is forecast to lift through central/eastern Montana into southern Saskatchewan, but there should be an axis of instability from the Central Plains, into northeast Montana. Moderate warm advection and a strengthening low level jet, combined with the shortwave lifting northeast through the area, should provide the forcing to develop isolated to scattered thunderstorms Wednesday night into Thursday. At this time the coverage looks to be pretty sparse with better chances west central into northwest and north central ND, but as the LLJ strengthens, isolated to scattered convection may spread north and east across the forecast area. Timing wise, for the most part it looks to be a Wednesday night event, so Wednesday currently looks to be mostly dry. If this timing holds and it's mainly an evening and overnight event with a strengthening LLJ, the main hazard would likely be quarter sized hail. Convection may linger into Thursday over eastern portions of the forecast area. With instability remaining strong over eastern ND and depending on the timing, there may be another shot of strong to possibly severe convection into Thursday afternoon. Think the better ingredients will be setting up to the east of the forecast area, but a strong to severe thunderstorm can't be ruled out from the Turtle Mountains into the James River Valley Thursday afternoon.

Friday and through the weekend the upper level low continues to spin over the Pacific Northwest, while upper level ridging builds strongly northward through the central and southern Plains and well into the Northern Plains. This will allow temperatures to really warm-up on Friday with highs in the mid and possibly even upper 90s in the southwest and south central. With the warm temperatures and

NBM ensemble temperature spreads are pretty low through Friday, especially west, but increase thereafter, thus confidence is rather high in a steady warming trend, especially west and south central through Friday, but confidence in temperatures lowers thereafter as there is a lot of uncertainty in the evolution of the western U.S. trough and central U.S. ridge pattern late in the weekend and especially into early next week. With the southwest upper level flow, at least a periodic chance of showers and thunderstorms seems reasonable Friday through Sunday. The western trough does look to lift into the central U.S. but the timing is highly uncertain at this time. There may also be a northern stream wave that may help flatten the central U.S. ridge as well. The NBM is depicting widespread moderate precipitation chances Sunday night through Monday evening. Whether this occurs or not, when the western low eventually does break down the upper ridge and ejects into the Central U.S. we should see a period of showers and thunderstorms with decent chances for some soaking rains. The NBM is currently depicting about a 30% (south) to 50% (north) probability of at least a half inch of rain in the 24 hour period ending at 12Z Tuesday. After temperatures top out on Friday, and remain warm Saturday, we should drop back down to near normal temperatures late in the weekend into early next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1150 AM CDT Tue Sep 1 2026

VFR conditions are expected across the forecast area, including all TAF sites through the 18Z TAF period. The exception could be areas of low stratus/fog in the southwest Wednesday morning. However, confidence is too low to mention at the KDIK airport at this time. Otherwise mainly high clouds north and mid-level and high clouds south, there may be a sprinkle or shower along the South Dakota border tonight into early Wednesday morning. Northwest surface flow over central ND will diminish and shift southeast later today. Southeast surface flow will continue through the forecast period over western ND. It may be breezy at times this afternoon southwest.

BIS WATCHES/WARNINGS/ADVISORIES

None.