textproduct: Bismarck

KEY MESSAGES

- Dense fog to linger across portions of western and northern North Dakota this morning.

- Critical fire weather conditions in far southwest North Dakota this afternoon and early evening.

- Chances for showers and thunderstorms increase through the holiday weekend. A few strong to severe thunderstorms could develop Saturday through Sunday.

- Well above normal temperatures today and Saturday, followed by a gradual cooling trend through the middle of next week.

UPDATE

Issued at 1015 AM CDT Fri Sep 4 2026

Fog is overall starting to improved across the state, however, observations and webcams still showing dense fog in western and northern portions. Decided to extend the Dense Fog Advisory for areas with lingering dense fog through the morning. Meanwhile, some showers and isolated thunderstorms are slowly moving northward out of South Dakota. If these hold together then some light rain is possible across the south later this morning into the afternoon. Added some slight pops to account for this shower activity.

UPDATE Issued at 643 AM CDT Fri Sep 4 2026

The early morning forecast remains on track. Widespread dense fog continues to impact all but far southwest North Dakota.

DISCUSSION

Issued at 528 AM CDT Fri Sep 4 2026

A low-amplitude ridge is building over the Northern Plains early this morning ahead of a deep longwave trough digging into the western CONUS. Broad surface high pressure over Manitoba/ Ontario is providing a weak easterly upslope surface flow into an antecedently moisture-rich air mass, which has resulted in widespread dense fog across much of western and central North Dakota. A Dense Fog Advisory is in effect for all but far southwest portions of our forecast area. The fog should lift during the mid to late morning hours as a deepening lee cyclone over central Montana strengthens southeasterly return flow over the western Dakotas. Surface winds are forecast to increase to around 25 mph in western North Dakota this afternoon, with gusts up to 35 mph. Meanwhile, the thermal ridge will also expand into western North Dakota this afternoon, bringing unseasonably warm temperatures as high as the mid 90s to southwest parts of the state, decreasing to more pleasant temperatures in the mid to upper 70s in the northeast. The combination of stronger winds and hot temperatures yielding RH as low as 15 percent is expected to result in critical fire weather conditions in far southwest North Dakota this afternoon and early evening. A Red Flag Warning is in effect for Golden Valley, Slope, and Bowman Counties.

The latest suite of CAMs shows low probabilities for convection initiating over parts of central North Dakota late tonight into Saturday morning in response to strong warm air and moisture advection induced by the nocturnal low level jet. Despite MUCAPE possibly increasing above 2000 J/kg, weak effective bulk shear and the elevated nature of the convection keeps severe probabilities very low. The upper level height ridge axis and underlying thermal ridge axis will become more focused over the Northern Plains on Saturday, keeping high temperatures well above normal in the mid 80s to mid 90s. Shortwave energy will begin ejecting from the base of the deep western CONUS trough on Saturday. There may be a narrow window for surface-based convection in southern North Dakota during the late afternoon and early evening hours on Saturday. Otherwise, elevated showers and storms could become more prominent Saturday night. In the event of surface-based convection, strong buoyancy and modest deep layer shear could support a few strong to severe thunderstorms across southern North Dakota during the late afternoon and evening. Severe probabilities should diminish late Saturday night, but lingering strong buoyancy could still support a pulse strong to severe storm.

Broad mid level height falls in response to a potent shortwave ejecting from the base of the western CONUS longwave trough keeps medium chances for showers and thunderstorms in the forecast for much of western and central North Dakota during the day Sunday, increasing to high chances (60 to 90 percent) Sunday night into Labor Day as the potent shortwave lifts northeast off the mountains of Montana and Wyoming. CAPE on the order of 2000 J/kg and effective bulk shear around 30-40 kts keeps a low risk for strong to severe thunderstorms in the forecast for nearly all of North Dakota on Sunday. As mentioned, the highest rain chances are focused from Sunday night through Labor Day as the upstream longwave trough begins to kick northeast. NBM probabilities for at least an inch of rain over the Sunday through Labor Day time period range from only around 10 percent in far southwest North Dakota to as high as 80 to 90 percent along the Canadian border. This disparity appears to be at least partially influenced by a dry slot attendant to a surface cyclone lifting northeastward through the region on Labor Day. The frontal boundary ushering in the dry slot could initiate a conditional severe risk in a lower CAPE/higher shear environment, but forecast confidence in convective details at this time range remains quite low. From Tuesday to Wednesday, an occlusion of the low is projected over the southern Canadian prairie provinces on Tuesday before it quickly jets toward the northern Great Lakes and New England. This favors drier, slightly cooler, and windier conditions for western and central North Dakota Tuesday and Wednesday. Flow aloft may then transition to quasi-zonal by the end of next week, which could moderate temperatures to near normal values and return periodic lower chances for rain.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 643 AM CDT Fri Sep 4 2026

Dense fog will impact much of western and central North Dakota early this morning, with conditions expected to improve by late morning/early afternoon. VFR conditions are then anticipated through the rest of the forecast period. A few isolated showers or thunderstorms could develop in central North Dakota late tonight, but the probability is not high enough to mention in any TAF at this time. Winds will become southeast today and strengthen to 15-25 kts, with gusts up to 35 kts in western parts of the state during the afternoon. Low level wind shear is forecast to impact parts of western and central North Dakota late tonight, especially from KMOT to KBIS.

BIS WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until noon CDT /11 AM MDT/ today for NDZ001>005-009-010-012-013-017-018-032-033-041-042-055-056-059. Red Flag Warning until 8 PM MDT this evening for NDZ031-040- 043.