textproduct: Bismarck

KEY MESSAGES

- Below normal temperatures continue this weekend, with highs about 5 to 10 degrees below average.

- High chances for rain showers (~70-100%) Sunday night into Monday. The greatest chances are over central and eastern North Dakota.

- Becoming windy late Sunday, with the strongest winds expected on Monday before diminishing Monday night. Gusts to 50 mph are possible over western North Dakota.

UPDATE

Issued at 106 AM CDT Sun Sep 13 2026

For late night update, have expanded low rain chances west a bit to pick up some activity around the Dickinson area. Otherwise, going forecast remains in good shape.

UPDATE Issued at 930 PM CDT Sat Sep 12 2026

Quiet weather is found across western and central North Dakota at the time of this mid to late evening update. A few blips of weak radar returns linger over the southwest and south central this evening, but have greatly diminishing over the last few hours. Short term CAMs continue to advertise the potential for some showers across portions of the south central into the southern James River Valley tonight through early Sunday morning as a upper level jet cuts across the area. Will maintain low (10 to 30 percent) chances for now. No major adjustments to the forecast were performed with this update, as it remains on track at this time.

UPDATE Issued at 615 PM CDT Sat Sep 12 2026

Weak radar returns persist across portions of southwestern and south central North Dakota at the time of this early evening update. Induced by the weak divergence found along the right exit region of an upper level jet, very dry conditions up to around 7kft above the surface has so far limited the amount of precpitation reaching the ground, if any indeed has. Low chances (10 to 30 percent) for precpitation is expected later this evening into early tonight as saturation of the column increases, though most locations are expected to remain dry. For this update, have blended the latest short term model trends into the PoPs to slightly increase coverage of showers in the south central overnight, but this change is relatively minor. Otherwise, the forecast remains in good shape.

DISCUSSION

Issued at 225 PM CDT Sat Sep 12 2026

This afternoon, broadly zonal flow was present over the Northern Plains, with a Hudson Bay low to the northeast and a secondary closed low just offshore of the Pacific Northwest. A shortwave aloft associated with the Hudson Bay low was over the central Canadian Prairies. At the surface, broad high pressure extended from east central Alberta into northwest North Dakota.

An embedded vort max in the mean flow has been producing light radar returns across southwest North Dakota throughout the day so far today, although we have to see any confirmation of any rain making it to the surface, which is not too surprising given the high ceilings. Northwest winds are a bit breezy with the surface pressure gradient, but will be diminishing through the rest of the day as the surface high continues to push across the state. Highs this afternoon will be in the upper 50s to upper 60s. Lows tonight will be seasonably chilly, mainly in the upper 30s to mid 40s, although we could see some mid 30s across the International Border.

We did contemplate whether or not a Frost Advisory would be needed tonight. Although the surface high moving in would typically favor temperatures dropping well below guidance, latest deterministic guidance is advertising a shortwave diving south from the Canadian Prairies overnight tonight. Recent CAMs runs are all in agreement on scattered precipitation across at least central North Dakota tonight, with forecast RH and BUFKIT soundings showing midlevel clouds extending across the forecast area. This, plus current satellite imagery showing widespread cloud cover upstream across southern Alberta and Saskatchewan, has us wondering how much clouds will clear out even as the surface high moves through and subsequently how much temperatures will drop below the deterministic NBM which is already skewed close to the 25th percentile. Some isolated frost is still possible mainly across our four northwest counties and into Renville and Bottineau Counties, but at this point we are not confident enough in widespread impacts to go ahead with an advisory. Forecasters this evening will re- evaluate.

On Sunday, the aforementioned deep closed low will continue to move onshore into the Pacific Northwest, with downstream shortwave ridging across the Northern Plains that will warm temperatures some for Sunday and Monday. Highs rebound back into the lower 60s to lower 70s on Sunday, and then the mid 60s to mid 70s on Monday. As the low approaches the region, expect widespread showers and occasional thunderstorms to start late Sunday evening across western North Dakota, expanding east through the night and Monday. NBM PoPs continue to be quite high especially for areas along and east of Highway 83, with a rainy Monday morning commute expected. This is the dividing line of a 50/50 chance for more than 0.50 inches of rain (east) and less than that (west). Showers and thunderstorms will end rather quickly from west to east through the day Monday as the upper low lifts northeast.

The main threat will be for localized heavy rain, with PWATs forecast around 1.5 inches which is towards the upper end of climatology for mid September. We are also expecting strong winds with this system, starting southeasterly on Sunday and switching to westerly on Monday behind the front that moves through. ECMWF EFI highlights southwest North Dakota as the area of most concern with a shift of tails across much of the forecast area, so current thought is wind gusts of 50 to 55 mph across western North Dakota on Monday.

We quickly return to zonal flow on Tuesday, with highs in the 60s but lighter winds after the early week system. Moderate chances for rain return on Wednesday as a progressive embedded wave moves in as synoptic flow turns more southwesterly across the region. NBM temperature percentiles signal a return to near normal temperatures by the end of the work week.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 106 AM CDT Sun Sep 13 2026

VFR conditions will prevail through the forecast period.

BIS WATCHES/WARNINGS/ADVISORIES

None.