textproduct: Bismarck

KEY MESSAGES

- Continued below normal temperatures for today.

- Temperatures will average above normal Monday through Wednesday, along with mainly dry weather conditions.

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

DISCUSSION

Issued at 244 PM CDT Sun Apr 19 2026

This afternoon, the Northern Plains were placed between a Hudson Bay low and a secondary low off the coast of British Columbia, with upper ridging beginning to build over the northern Rockies and subsequent downstream cyclonic flow over the region. At the surface, broad high pressure was analyzed over eastern North Dakota, with some fair weather cu around the center of the low. Sunshine increases to the west, with a bit of a breeze developing this afternoon from mixing and a tightening surface pressure gradient. Seasonably cool temperatures continue, with highs in the 40s north and east to the upper 50s far west.

Low level warm air advection strengthens tonight and we begin to warm up in earnest to start the work week, with breezy to strong southwest winds tonight through Monday. Main weather concern on Monday is near critical fire weather conditions in the southern James River Valley, where there is the most favorable overlap of the strong southwest winds and minimum relative humidity from 25 to 35 percent. Lower humidity exists in the southwest, but lighter winds will limit fire weather concerns in this area. Highs on Monday will be in the mid 60s to mid 70s, with some passing clouds from an impulse to our northeast.

Temperatures warm up further on Tuesday and Wednesday, with increasing southerly low-level flow as the deep low moves onshore to the western CONUS. Highs peak on Wednesday in the lower 70s north to mid 80s far south, although the deterministic NBM is below the 25th percentile, so wouldn't be surprised if the forecast highs keep increasing in future runs.

Ensemble guidance is in good agreement on the aforementioned deep trough ejecting over the Rockies midweek, with precipitation chances quickly increasing for the back half of the work week. Wednesday evening will be the main window for thunderstorms, with deterministic guidance advertising sufficient instability and shear for potentially a few stronger storms. CSU and NSSL machine learning guidance both highlight a north-south axis of increased probabilities across south central North Dakota and the James River Valley.

As the upper low closes off and tracks through the Dakotas on Thursday, blended POPs are already showing widespread 60 to 80 percent chances for showers and thunderstorms, with a medium chance for at least half an inch of QPF across western and northern North Dakota. Temperatures will range across the area as the associated cold front moves through the state, with highs occurring early in the day in the northwest where the front gets to first. Forecast highs are in the mid 40s northwest to upper 60s southeast.

With the overall setup and the strength of the low, it is no surprise that the ECMWF EFI is already advertising potential for strong winds, with a shift of tails across the majority of North Dakota Thursday and Friday.

Precipitation chances lesson late Thursday into Friday, although the general expectation is for another closed low to drop south from the southern Canadian Prairies and be absorbed into the broader trough. Much colder air is expected behind the system, with lows in the mid 20s to lower 30s Friday morning, and highs on Friday mainly in the mid 30s to mid 40s. Expect similar temperatures on Saturday, and with low POPs continuing through this period, snow becomes the dominant p-type. The likelihood of measurable snow is broadly 40 to 60 percent north and west where temperatures stay colder, with a low chance of exceeding an inch of new accumulation.

Winds stay elevated on Saturday but diminish further on Sunday, although temperatures still look seasonably cool in the 40s. Below normal temperatures are favored through the end of the month.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1248 PM CDT Sun Apr 19 2026

Overall VFR conditions expected through the 18Z TAF period, although some low VFR cumulus are ongoing in the James River Valley to start the period. Light and variable winds will become southerly and breezy overnight tonight, shifting to become more westerly late in the period. LLWS was included at KBIS and KMOT overnight into Monday morning.

BIS WATCHES/WARNINGS/ADVISORIES

None.