textproduct: Bismarck

KEY MESSAGES

- Temperatures will continue to average well above normal both Tuesday and Wednesday, along with mainly dry weather conditions.

- Active weather pattern is favored Wednesday night through the end of the week, with medium to high precipitation chances along with a strong cooling trend.

- Strong northwest winds are possible Thursday and Friday.

UPDATE

Issued at 645 PM CDT Mon Apr 20 2026

Limited updates needed this evening as clear to mostly clear skies remain. Some breezy westerly winds combined with low RH values could provide for some near critical fire weather conditions through sunset this evening. Overall the forecast remains on track.

DISCUSSION

Issued at 247 PM CDT Mon Apr 20 2026

This afternoon, the synoptic pattern was characterized by troughing over the eastern CONUS, with a stronger closed low and attendant troughing off the coast of California. Flow over the Northern Plains was weakly cyclonic, with a weak frontal boundary moving through North Dakota, extending from a surface low well to our northeast in Manitoba. Behind the boundary, winds were turning more northwesterly, with a few high clouds passing through but lots of sunshine and highs in the upper 60s north to lower 80s southwest this afternoon. Near critical fire weather conditions are expected in both the southwest and the southern James River Valley this afternoon, otherwise no big weather concerns in the near term.

Quiet and warm weather continues on Tuesday, with highs similar to today, and breezy southerly winds. We start to see more changes midweek as the aforementioned closed low moves onshore and amplifies heights over the region on Wednesday, with temperatures peaking this day in the mid 70s north central to around 90 southwest. As the trough base moves over the Northern Rockies, surface low pressure will begin deepening in central Montana, with strong southerly low-level flow out ahead of the system. Wednesday will be quite windy and warm across the forecast area, with some question on how high dew points end up due to moisture advection. Generally looks like 500-1000 J/kg of instability available per deterministic guidance, with very marginal shear but falling heights to support showers and thunderstorms Wednesday evening as the larger system approaches the area. Although we are not currently outlooked by SPC in anything beyond general thunder, worth nothing that both NSSL and CSU machine learning guidance has low probabilities for severe weather focused across central and eastern North Dakota.

As the low becomes stacked on Thursday, precipitation chances increase and become widespread, with the highest chances of rain around 80 percent in western North Dakota. There could be some isolated thunderstorms during the day Thursday as well, but that window ends quickly as temperatures fall through the day on the backside of the system. With cooler air surging in, precipitation is favored to transition from rain to snow Thursday night, with low to medium POPs continuing through Friday as the upper low absorbs another lobe moving south from the Canadian Prairies. Although snow accumulations will be highly dependent on how the low tracks and when profiles turn cold enough for snow, latest NBM 5.0 data has a medium to high chance for measurable snow across western and northern North Dakota, with a 20 to 40 percent chance for at least 4 inches of snow across the far northwest.

The other concern with this system is winds, especially with the low projected to become stacked. Background synoptic winds with these systems get to be quite strong, with the current expectation for widespread advisory criteria, if not approaching warning criteria. ECMWF EFI continues to advertise the wind potential, although perhaps not as strong as one would think based on the general pattern. Current forecast looks strongest on Thursday, although still strong on Friday and breezy on Saturday.

The other discussion point with this system is temperatures. Quite a gradient on Thursday as the attendant front moves through, with highs in the lower 50s west to lower 70s east, and many locations seeing their high temperatures early in the day. There is then high confidence in well below normal temperatures through the weekend, generally from the 30s north to 40s south.

Although blended POPs taper off on Saturday, would not be surprised to see wrap-around light precipitation (either rain or snow) linger through Saturday and potentially into Sunday. Ensemble guidance seems fairly set on the low very slowly lifting north through the weekend, which will keep us under its influence for longer. There are also signs of another system tracking to our south late in the weekend, with broadly cyclonic flow continuing into next week. Below normal temperatures are favored through the end of the month.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 645 PM CDT Mon Apr 20 2026

VFR conditions are expected through the forecast period. Look for mainly clear skies tonight through Tuesday morning, with perhaps some fair weather cumulus Tuesday afternoon. West winds will become east southeast tonight, with some periods of light and variable winds. Tuesday then sees southerly and breezy at times winds for most sites.

BIS WATCHES/WARNINGS/ADVISORIES

None.