textproduct: Bismarck

KEY MESSAGES

- Dry with well above normal temperatures today through Saturday. Highs mostly in the 70s and 80s.

- Much colder with medium to high chances for rain late Saturday night through Monday. Snow could briefly mix with rain in western parts of the state late Sunday night into Monday morning.

- Widespread below freezing temperatures possible Monday night.

- A stronger system could bring windy and rainy conditions to the region mid to late next week.

DISCUSSION

Issued at 319 AM CDT Fri Oct 9 2026

A potent shortwave digging into the Pacific Northwest this morning will turn northwest flow aloft over the Northern Plains into low- amplitude ridging. The shortwave will also force lee cyclogenesis from southern Alberta to central Montana, placing the Dakotas under southerly return flow with strong warm air advection. Given very little spread in the NBM temperature distribution and recent observed biases, we have raised the high temperature forecast for today to near the 75th percentile, giving lower 70s northeast to mid 80s southwest. The southerly flow will continue through tonight as the lee trough pushes eastward, advecting unseasonably high dewpoints in the mid 50s into central and eastern North Dakota. Forecast low temperatures tonight in the upper 40s to upper 50s approach near-record warm values.

By Saturday morning, the lee trough is projected to have entered western North Dakota as a cold front within a broad area of low pressure attendant to a deeper surface low over southern Saskatchewan. The cold front is projected to lie from the northern Red to southern James River Valleys by the end of the day, although some timing uncertainty is evident. The high temperature forecast along and ahead of the front's most likely location at midday, roughly from the Devils Lake Basin to south central North Dakota, was raised closer to the NBM 75th percentile. This gives an area-wide forecast of mid 60s northwest to mid and even upper 80s in the southern James River Valley.

The magnitude of low level cold air advection trailing the cold front is not overly strong, but a long duration of persistent cooling is forecast to last through the day Sunday. The leading edge of the low level baroclinic zone could stall over southeast North Dakota on Sunday, but all locations are projected to have highs around 20 to 25 degrees colder than Saturday, ranging from the 40s northwest to 60s southeast. The entire NBM distribution has warmed slightly from previous iterations, which is noteworthy given increasing precipitation chances from Saturday night through Sunday evening driven by DCVA, a split upper jet, and transient low to mid level frontogenesis. Ensemble mean QPF and threshold probabilities have slightly decreased and slightly shifted northward compared to previous forecasts. Through Sunday evening, a triangular area of 50 percent or greater chances of at least a tenth of an inch of rain is generally enclosed by a line from the southwest to northeast corners of the state and the Montana and Canadian borders. Confidence that temperatures will remain above freezing over this time period is very high.

Most guidance shows a brief break in precipitation chances late Sunday evening before another wave of DCVA ejects from the base of a western CONUS trough. Previous forecasts had noted strong jet dynamics with this second round of DCVA, but recent deterministic models now favor the left exit region of the southern jet streak to remain much further south. There is still sufficient forcing for ascent to produce widespread precipitation late Sunday night through Monday, and transient mid level frontogenesis could enhance precipitation rates at times. The NBM places at least a 40 percent chance for exceeding a tenth of an inch of QPF over all but southeast North Dakota, which lines up well with 2 ensemble clusters that are comprised of two thirds of the total global ensemble membership. The highest QPF probabilities (around 60-80% for exceeding 0.1" and 40-60% for exceeding 0.25") are placed over western North Dakota, but clusters reveal north-to-south uncertainty where the highest amounts could fall. The slight warming trend of the NBM temperature distribution is carried through Monday, with Sunday night lows now forecast to remain above freezing at most locations. Given this combined with slightly weaker forcing lowering the dynamic cooling potential, the probability for snow has greatly diminished. There could still be a brief rain/snow mix in western parts of the state early Monday morning, but the probability of just a tenth of an inch of snow has fallen to no greater than 10 percent.

The high temperature forecast on Monday has risen slightly, but still remains below normal at around 45 to 50. There is uncertainty on how quickly rain will diminish, which could be as early as late Monday afternoon or as late as early Tuesday morning in some locations. This could have great implications on the Monday night low temperature forecast, as any areas that become cloud free will be very likely to see below freezing temperatures. Lows could still approach freezing even underneath cloud cover, but there is still very little to no chance of any lingering precipitation changing over to snow.

From Tuesday to Wednesday, ensemble mean height fields generally depict a cutoff low ejecting from the Desert Southwest as another shortwave digs into the Canadian Rockies. This places brief upper ridging over the Northern Plains, but the colder air mass in place could become trapped in a poorly mixed boundary layer. Nevertheless, the high temperature forecast improves into the 50s for all areas Tuesday through Thursday. Global ensembles show very high confidence that the remnants of the cutoff low will initiate lee cyclogenesis over Colorado during the middle of the week, but there is considerable uncertainty in the timing and track of the surface low, to the point that no other takeaways can be made other than the likelihood of its existence. Precipitation chances begin to increase on Wednesday and are maximized at around 50 to 70 percent Wednesday night. The interesting thing to watch will be how the potential Colorado low may interact with the aforementioned Canadian shortwave and whether the latter will advect cold enough air to change rain over to snow before precipitation departs the region by the end of the work week. The other concern with this system that would be most impactful in the absence of snow is the potential for strong winds. Global ensembles are already showing medium probabilities for 850 mb winds exceeding 40 kts and low probabilities for exceeding 50 kts Thursday into Friday, and these probabilities are highest in the highest-membership clusters.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 319 AM CDT Fri Oct 9 2026

VFR conditions are expected through the forecast period. Winds will become southerly around 15 kts this afternoon, with gusts to around 25 kts. A 10-15 kt southerly wind will persist through the evening, with low level wind shear developing at KJMS and surrounding areas around 03Z.

BIS WATCHES/WARNINGS/ADVISORIES

None.