textproduct: Bismarck

KEY MESSAGES

- Slightly cooler today and Saturday, then hot again for most areas on Sunday.

- Temperatures are favored to fall closer to normal next week, with forecast highs mostly in the 80s.

UPDATE

Issued at 1235 PM CDT Fri Jul 17 2026

Dense Fog Advisory was canceled at 16z, as conditions quickly improved after the extension. The elevated showers continue to slowly move east into south central North Dakota. The latest NBM was loaded into the forecast.

UPDATE Issued at 940 AM CDT Fri Jul 17 2026

Shrunk and extended the Dense Fog Advisory in the northwest until noon. There are several sites that visibilities are less than 0.25 miles, along with several webcams. There are still several elevated showers in the southwest as well.

UPDATE Issued at 644 AM CDT Fri Jul 17 2026

The Dense Fog Advisory was recently expanded into the rest of Ward, Renville, and Bottineau Counties. Elsewhere, the MCV in southeast Montana has been slowly dissipating as it approaches the North Dakota border. Some light could still fall south of I-94 and along and west of Highway 85, but the probability of lightning has fallen to near zero.

UPDATE Issued at 527 AM CDT Fri Jul 17 2026

Quick update to add Dunn, Mercer, and western McLean Counties to the Dense Fog Advisory.

DISCUSSION

Issued at 452 AM CDT Fri Jul 17 2026

The prolonged upper level ridge has been flattened early this morning by several shortwaves to the west and north of the local area. One of these shortwaves is responsible for an MCS moving across southeast Montana which is now approaching southwest North Dakota. The MCS has been in an area of sparse observations as of late, but the surrounding wind field would suggest that this has turned into an MCV, which has already outlived even the longest projections by earlier CAMs. And the HRRR has been consistently showing an unrealistic evolution from its assimilation at forecast hour zero to forecast hour one. So confidence is low on how long the MCV will persist and what kind of weather it may bring to southwest North Dakota early this morning. Frequent forecast updates may be needed if rapid refresh guidance continues to struggle as much as it has been overnight. Severe weather has not been observed for quite some time, and the downstream environment does not appear to be any more favorable for stronger convection than what it is moving through at the moment. If the MCV survives into southwest North Dakota, the main hazards will likely be just lightning and rain, but rainfall could be heavy if the system maintains its very slow forward motion.

The other forecast concern early this morning is dense fog in northwest North Dakota. The fog is placed well behind a weak cold front that has reached south central to northeast North Dakota, but the trailing northerly flow has cooled the boundary layer at a much quicker rate than it has dried out. Rapid refresh guidance seems to be handling the fog quite well, which keeps the greatest concentration of dense fog limited to the current advisory area and dissolves it near the expiration time of 10 AM CDT.

Except for the far northwest, today should be at least a few, if not several degrees cooler than yesterday with highs in the mid 80s to mid 90s. Flow aloft will turn northwesterly today as a Manitoba/Ontario shortwave digs toward Lake Superior, shunting the persistent ridge back west toward the Northern Rockies. Aside from the unknowns involving the morning MCV, surface high pressure sliding down from Saskatchewan should provide for a quieter day. The upper ridge axis is forecast to shift back over the Northern Plains on Saturday ahead of a series of shortwaves ejecting off the Northern Rockies. Some CAMs show that the lead shortwave could produced high-based showers as it moves through during the day Saturday, but there are wide variations in coverage, placement, and timing. The risk for thunderstorms through Saturday afternoon is actually quite low with ensemble guidance showing high confidence in an unusually stable air mass not only given the time of year, but also given that forecast highs on Saturday remain in the mid 80s to mid 90s. The highest chances for showers and thunderstorms via the NBM have consistently been over the Saturday evening into Sunday morning time period. While its percentages have decreased slightly from previous forecasts, there is so far little to no support from any CAMs that have reached this forecast time range for anything more than a few stray showers prior to early Sunday morning.

A more potent shortwave ejecting off the Canadian Rockies on Sunday will drag the top of the thermal ridge back over the Northern Plains. Forecast highs keep trending upward on Sunday and are now solidly around 95 to 100 across most of western and central North Dakota. Another Heat Advisory may be needed on Sunday, especially in south central North Dakota where forecast maximum heat indices are around 100 and the maximum wet-bulb globe temperature risk reaches the Extreme category. The timing of the passage of the shortwave through the southern Canadian prairie provinces and its attendant southward extending surface trough could initiate convection in parts of the region Sunday afternoon and evening, but forecast details for this remain uncertain at this time range.

Ensembles show a much cooler air mass being driven into the region early next week as a farther north and more potent shortwave joins the southern Canadian shortwave and dives into the Great Lakes. The attendant, stronger cold front may not reach southern North Dakota until Monday evening or night, where forecast highs on Monday are still in the lower to mid 90s. But northern parts of the state are favored to cool back down into the 80s on Monday. The NBM favors Tuesday being the coolest day before the western reaches of the cooler air mass depart, with highs in the mid 70s to mid 80s. A northwest flow pattern is favored for the rest of next week, with uncertainty in whether or for how long the upstream ridge will remain back over the Rockies. This pattern lends to low predictability for any shower and thunderstorm chances, which generally remain under 20 percent in the current iteration of the NBM through next week. But there is higher confidence in Tuesday being a dry day with a large high pressure favored to be centered over the region.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1235 PM CDT Fri Jul 17 2026

VFR through the period with MVFR in the James River Valley early today. Winds will around 10 knots from the north this afternoon, turning to the south by Saturday morning.

BIS WATCHES/WARNINGS/ADVISORIES

None.