textproduct: Bismarck

KEY MESSAGES

- Areas of dense fog along and east of Highway 83 through mid Sunday morning.

- Isolated to scattered showers will move across the state from southwest to northeast through Sunday morning. A few thunderstorms with gusty winds are also possible.

- Above normal temperatures for the most part through the middle of next week, with additional medium to high chances for rain on Monday.

- Significant cool down possible for the end of next week, with medium chances for both rain and snow.

UPDATE

Issued at 105 AM CDT Sun Apr 12 2026

Main update is for the expansion of the Dense Fog Advisory northward to include Bottineau, McHenry, Renville, Ward, and McLean Counties. Observations and webcams in these areas starting to show fog develop and should be dense through the night into Sunday morning. Meanwhile, showers with some thunderstorms continue to push across the west. The threat for severe weather has diminished somewhat, although some gusty winds up to 50 mph are still possible from isolated thunderstorm activity through tonight.

UPDATE Issued at 1059 PM CDT Sat Apr 11 2026

A cluster of decaying thunderstorms has entered southwest North Dakota late this evening, producing wind gusts as high as around 55 mph. Do not anticipate winds of this magnitude will translate too much farther downstream. Will also need to monitor a line of thunderstorms approaching northwest North Dakota within the next few hours that has been routinely producing gusts as high as 60 mph in northeast Montana, and is entering an environment with at least 1,000 J/kg DCAPE per SPC mesoanalysis.

The Dense Fog Advisory has been expanded westward into Sheridan, Burleigh, and Emmons Counties.

UPDATE Issued at 849 PM CDT Sat Apr 11 2026

Webcams from the Turtle Mountains through the James River Valley and adjacent areas to the west show visibility deteriorating. A Dense Fog Advisory has been issued until 10 AM CDT Sunday morning. The advisory may need to be expanded westward later tonight.

UPDATE Issued at 729 PM CDT Sat Apr 11 2026

Already seeing signs of visibility lowering in the James River Valley. Have increased and expanded the coverage of fog across central and into eastern North Dakota this evening through early Sunday morning. Webcams have also shown signs of drizzle in the southern James River Valley, where a patchy mention has been added to the forecast through mid evening. RAP guidance suggests the depth of the near-surface saturated layer will become less favorable for drizzle overnight.

Scattered showers and isolated thunderstorms were entering southwest North Dakota at the time of this writing. No notable wind gusts have been observed upstream in southeast Montana and northwest South Dakota, and there have only been brief spikes in reflectivity with a couple of storms to the southeast of Miles City. SPC mesoanalysis shows increasing surface and mixed-layer CIN, which is related in the latest lightning observations. But downstream MUCAPE is still around 1000 J/kg, so cannot rule out a thunderstorm or two in southwest North Dakota through the evening. Brief downpours and perhaps some very small hail no larger than pea-size would be the expected hazards with the strongest storm.

DISCUSSION

Issued at 253 PM CDT Sat Apr 11 2026

This afternoon, a deep trough and closed low were placed off the California coast, leading to downstream southwest flow across the Dakotas. At the surface, a broad area of low pressure was analyzed over eastern Montana, with a moderately tight surface pressure gradient across the forecast area that was producing breezy southeasterly winds. There is also a large area of low stratus that extends from the Turtle Mountains through the James River Valley and east, and goes far enough west to be on the edge of the Bismarck/Mandan area. Low confidence in the progression of the western extent, but high-res guidance all agrees on our eastern counties being socked in for the rest of today and through tonight. Underneath this stratus are afternoon temperatures in the 40s and occasionally some drizzle in the eastern James River Valley. Meanwhile, western North Dakota has plentiful sunshine and afternoon highs in the 60s and 70s.

Just upstream, we are already starting to see some scattered convection develop with a shortwave and 300mb jet streak moving through the mean southwest flow over Wyoming, with activity expected to move into southwest North Dakota this evening before expanding across the forecast area tonight. Carrying a broad 20 to 40 percent chance of showers and thunderstorms, with deterministic guidance showing at most a few hundred j/kg of instability available for some rumbles of thunder across the west and central. The other main forecast concern tonight is fog development across the eastern half of the state underneath the low stratus, with patchy fog included in the gridded forecast into Sunday morning.

Precipitation chances taper off Sunday morning as the upper wave and attendant surface low exit to the northeast, with skies clearing and winds turning more westerly and breezy. Sunday looks like the warmest overall day of the period, with forecast highs in the upper 50s north to the mid 70s south. We did opt to skew up to NBM50 for forecast high temperatures and blended down dew points just a touch, due to the west- northwest winds forecast and the deterministic NBM being on the cool side of the ensemble spread.

The next round of precipitation comes late Sunday through Monday, as another wave ejects out of the trough base that will be over the western CONUS. Some guidance wants to have a more northern stream wave separate from the main trough, but regardless, there's decent ensemble agreement on precipitation chances as latest NBM POPs are up to 60 to 80 percent across western North Dakota on Monday. There are low to medium chances for at least a quarter inch of QPF with this event, focused over western North Dakota.

Temperatures stay seasonable Tuesday and Wednesday with not too much wind, and low chances for rain focused on far southern North Dakota as a few waves pass to our south. Focus then turns to late in the week as a more substantial shortwave is progged to move in from our west, bringing chances for rain and snow as well as much cooler temperatures to end the work week. It is worth noting all four ensemble clusters have at least some snow associated with this system, and certainly more confidence in the cooler air moving in, but plenty of details to be worked out before then.

There are then hints of cooler than normal temperatures continuing into the week 2 period and potentially beyond, although average highs increase to the lower 60s by the end of the month. The active pattern is also favored to continue at least broadly across the region.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 105 AM CDT Sun Apr 12 2026

LIFR ceilings will prevail across the eastern half of North Dakota through tonight, mainly from KMOT to KBIS and eastward, including KJMS. Fog is also likely under the low clouds later tonight into Sunday morning, and may become dense. The low clouds are forecast to gradually lift and erode from southwest to northeast through the day Sunday. Some rain showers are possible as these low clouds lift.

Scattered showers and isolated thunderstorms are possible across western North Dakota through the overnight hours. The chance of scattered showers then spreads northeastward into Sunday morning and departs to the northeast Sunday afternoon. A brief period of MVFR to IFR conditions and strong wind gusts could occur with heavier showers and storms.

Southeasterly winds will gradually weaken tonight, then turn to the west-northwest on Sunday around 15-20 kts.

BIS WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 10 AM CDT this morning for NDZ003>005- 011>013-021>023-025-035>037-046>048-050-051.