textproduct: Bismarck

KEY MESSAGES

- Seasonably cold and rainy through Monday. The highest rain chances are across western and northern North Dakota.

- Rain could mix with or change over to snow in far northwest North Dakota late tonight through Monday morning. There is a low potential for light snow accumulations on grassy surfaces.

- Near to below freezing low temperatures are possible throughout the upcoming week.

- A mid to late week system could bring light precipitation and gusty winds to parts of the region.

DISCUSSION

Issued at 442 AM CDT Sun Oct 11 2026

A deep longwave trough axis lies from the Pacific Northwest to the coastal waters off southern California early this morning. Aside from the remnants of Isaias, the Gulf Coast and eastern CONUS are under upper level ridging. This places southwest flow aloft over the Northern Plains. A surface cold front has cleared all but the southeast corner of the state and is trailed by a low level baroclinic zone. Numerous shortwaves are forecast to eject from the base of the western trough today through Monday. The associated DCVA paired with broad isentropic ascent keeps precipitation chances in the forecast through Monday afternoon, diminishing Monday evening and overnight as the deep western trough cuts off from the northern stream. The highest chances for precipitation (90 to 100 percent) remain confined to west central and northern North Dakota, though the rest of our forecast area is still likely to see periodic light rain showers at times (60 to 80 percent chance). The time period with both the highest precipitation chances and QPF is tonight into Monday morning with a more potent mid level shortwave. Mesoscale forcing and instability do not appear that impressive, but the potential for a long duration of steady precipitation could produce QPF as high as one half to one inch, with the HREF probability-matched mean showing this potential along and northwest of a line from Beach to Bottineau. This lines up with the NBM showing high chances for exceeding half an inch and low to medium chances for exceeding one inch over this same area.

Very little diurnal heating is expected this afternoon under thick cloud cover and north-northeast surface flow reinforcing the cooler air mass. Forecast highs today range from the lower 40s northwest to upper 50s in the southern James River Valley. Forecast lows tonight range from near freezing in the northwest to the lower and mid 40s southeast. The colder temperatures in the northwest could allow rain to mix with or change over to snow late tonight into Monday morning, and there is now a potential outcome of precipitation remaining snow through Monday afternoon. HRRR/RAP soundings at Crosby show a deep isothermal layer that hovers near freezing until early Monday morning before cooling and remaining below freezing. But there is still support from other guidance for the deep isothermal layer to stay closer to freezing until late Monday afternoon, at which time precipitation may already be winding down there. NBM probabilities for measurable snowfall have increased, and are now as high as 40 to 60 percent across parts of Divide and Burke Counties, and 20 to 40 percent in northern Williams County. The probability for exceeding an inch of snow is no higher than 15 percent in northwest Divide County, but the HREF maximum snowfall there is greater than 2 inches. However, these snow amounts and threshold probabilities are not fully taking into account lower snow-to-liquid ratios (less than 10:1) and the high probability of melting on contact with the warmer ground (in the absence of enhanced snowfall rates). It should be noted that there are steep lapse rates through and above the dendritic growth zone, but the strongest forcing remains below the DGZ. The HREF probability for hourly snow rates exceeding just half an inch are less than 20 percent, rendering the 06Z HRRR's production of several inches of snow in Divide County a significant statistical outlier.

Monday looks to be the coldest daytime period through at least Thursday, and possibly well beyond. Forecast highs range from the lower 40s northwest to mid 50s in the southern James River Valley. Would not be surprised to see maximum temperatures verify slightly cooler on Monday given the extensive cloud cover and precipitation, especially in the far northwest where, as mentioned above, there is a low probability of snow falling throughout the day. Despite precipitation moving out Monday night and surface high pressure beginning to build in, models show high confidence in an overcast sky persisting through the night. The probability of a widespread freeze Monday night continues to decrease, and we are now forecasting lows to remain near to above freezing at most locations.

On Tuesday, the western cutoff low is forecast to park over Utah. Flow aloft over the Northern Plains remains cyclonic with the passage of a northern stream shortwave, but underlying surface high pressure keeps precipitation chances around 10 percent or less. Cloud cover could linger through the day though, and forecast highs only improve to around 50 to 55. The rest of the week continues to be marked by uncertainty in the evolution of the western cutoff low, as well as that of a potent shortwave moving from British Columbia to the Great Lakes. Theoretically, there are 4 distinct potential outcomes pairing whether the cutoff low ejects east of the Rockies and how far south the Canadian shortwave dives. Ensemble cluster analyses hone in on 2 of those 4: 1) the cutoff low ejects eastward and interacts with the Canadian shortwave over the Northern Plains and 2) the cutoff low never makes it east of the Rockies and the Canadian shortwave passes by to the north. But the support for each of these outcome varies by clusters' 24-hour analysis period, with outcome #1 ranging from 41 to 54 percent and outcome #2 ranging from 46 to 59 percent. It is therefore difficult to say either outcome is favored over the other at this time. Outcome #1 would be far more impactful to North Dakota, with higher rain chances (Wednesday night-Thursday night) stronger winds (Thursday-Friday), and much colder temperatures (Thursday night-Friday night). A much lower- membership (15 percent) cluster that supports outcome #1 would also introduce wrap-around light snow with strong winds on Friday. In stark contrast, outcome #2 keeps all but some very light rain south of North Dakota, a shorter duration of weaker but still gusty winds (Thursday-Thursday night), and warmer temperatures with high pressure moving in on Friday.

Despite the uncertainty in the synoptic pattern through the end of the work week, there is actually lower ensemble spread next weekend with a higher-amplitude ridge over the Northern Plains transitioning to a quasi-zonal flow pattern. The spread of the median 50 percent of the NBM maximum temperature distribution drastically shrinks by Sunday, favoring above normal highs in the 60s into the following week.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 442 AM CDT Sun Oct 11 2026

Periods of rain can be expected across western and north central North Dakota through the forecast period, with periodic chances for scattered showers in south central North Dakota. The rain may cause MVFR visibility at times. MVFR to IFR ceilings are also forecast across all of western and central North Dakota this morning and afternoon, falling to IFR/LIFR levels tonight. Winds will remain north to northeast around 10-15 kts through the forecast period, with some higher gusts at times.

BIS WATCHES/WARNINGS/ADVISORIES

None.