textproduct: Bismarck

KEY MESSAGES

- Near average temperatures through the middle of next week, with highs mostly in the upper 70s to upper 80s.

- Low to medium chances (30 to 50 percent) for showers and thunderstorms late Saturday into early Monday.

UPDATE

Issued at 640 AM CDT Thu Aug 20 2026

The forecast remains in good shape. Radar continues to show light shower activity from near Harvey to Jamestown to Oakes, but much of this may not be reaching the ground and is likely only producing trace amounts at most. Quiet weather should prevail today, with breezy northwest winds in the eastern half of the state.

DISCUSSION

Issued at 340 AM CDT Thu Aug 20 2026

Northwest flow pattern continues over the Northern Plains early this morning between a Hudson Bay low and Desert Southwest ridge. Two pockets of isolated showers from north central North Dakota to the southern James River Valley are traveling east- southeastward. The northern showers should remain very light, but lightning has become consistently observed in LaMoure and Dickey Counties. Nevertheless, these thunderstorms will soon be departing the forecast area. Dry weather is anticipated for the rest of the day as weak surface ridging builds down from Saskatchewan. High temperatures this afternoon should be similar to those observed yesterday, except a bit cooler across the far north, ranging from the mid 70s in the Turtle Mountains to near 90 in the far southwest.

Another low-amplitude shortwave embedded in the northwest flow is forecast to move through the state on Friday. Most guidance produces at least some shower activity moving from northwest North Dakota in the morning through central and into southeast North Dakota through the afternoon, with the HRRR and NAMnest being notably more bullish on coverage and QPF (albeit still very light). Despite strong vertical shear, ensemble guidance shows little to no CAPE on Friday, keeping thunderstorms out of the forecast. The upstream ridge is forecast to become highly- amplified over the Rockies heading into the weekend before being shoved eastward by a potent shortwave landing on the Pacific Northwest coast. But the eastward progression of these features could also be stagnated by a downstream trough digging into the Great Lakes. Saturday should remain dry during the daytime with the Northern Plains under deep-layer subsidence. Later Saturday night into Sunday, weaker shortwave energy preceding and loosely associated with the more potent Pacific Northwest wave could begin ejecting into the Northern Plains. Then from Sunday night into Monday, the potent shortwave is forecast to eject off the Canadian Rockies into the southern prairie provinces, with southward extending frontal boundaries traversing North Dakota. This gives us the highest chances for a more widespread rainfall over the 7-day forecast period. NBM PoPs have risen slightly, with maximum values around 30 to 50 percent at any given location and temporally highest Sunday evening. There is still timing uncertainty for when the strongest forcing will cross western and central North Dakota, but a late afternoon/ evening passage on Sunday could support strong to severe convection as models show a plume of higher mixing ratios advecting poleward through moderate to high deep layer shear. Confidence in the severe storm potential is quite low however, as deterministic model soundings show a capping inversion and CSU machine learning severe probabilities remain under 5 percent. There is also a low probability outcome that the progression of the Canadian shortwave could be slowed enough for a thunderstorm risk to remain in central/eastern North Dakota through Monday afternoon.

Ensemble consensus favors the Canadian shortwave digging southeastward toward the Great Lakes by the middle of next week as the western CONUS ridge re-amplifies once again. Beyond that point in time, ensembles begin to diverge on whether the ridge axis will shift back over the Plains or remain stationed over the Rockies through the second half of next week. Despite all the aforementioned regional pattern shifts, the NBM shows very small variability in day-to-day temperatures through the middle of next week, with near average highs in the upper 70s to upper 80s and overnight lows around 50 to 60. Analysis of distribution trend lines shows that Monday is favored to be a comparatively warmer day at most locations.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 640 AM CDT Thu Aug 20 2026

VFR conditions are expected through the forecast period. A few stray showers are possible near KJMS early this morning, with no impacts to aviation. Winds will become northwest around 10-15 kts later this morning through the afternoon, with gusts to around 20-25 kts.

BIS WATCHES/WARNINGS/ADVISORIES

None.