textproduct: Bismarck

KEY MESSAGES

- Periods of isolated to scattered showers and thunderstorms are expected through the holiday weekend. A few storms may be strong to severe. The highest chances for showers and storms are from Sunday night into Labor Day.

- Unseasonably warm and humid through the holiday weekend, then trending cooler.

- Windy on Tuesday, with near-critical fire weather conditions in southwest North Dakota.

UPDATE

Issued at 157 AM CDT Sun Sep 6 2026

Only minor forecast adjustments were made for this update, mainly to PoPs. A small cluster of scattered showers and thunderstorms is moving through far southeast Montana, but radar and satellite show dissipation on the leading eastward flank. We did maintain 15 to 20 percent PoPs across the north where low level warm air advection and moisture transport are maximized, but at the time of this writing there were no imminent signs of convective initiation anywhere in the state.

UPDATE Issued at 1027 PM CDT Sat Sep 5 2026

Thunderstorms have moved out of the area. Quiet weather continues across the region.

UPDATE Issued at 614 PM CDT Sat Sep 5 2026

A line of thunderstorms continue to move across north central South Dakota and continues to spill into south central North Dakota. This line has produced ping pong size hail at times in South Dakota. The North Dakota portion of the line produced outflow weakening the storms behind the outflow. Also the anvil cirrus continues to increase CIN upstream of the storms. There is another lone cell moving across the International Border that is sub severe at the moment. There is widespread instability, but weak shear across the state which has lead to these strong multicellular storms pulsing up quickly then falling apart cause there is not enough shear to keep storm organized. The CAMs do not really have much development this evening into tonight as these storms weaken.

DISCUSSION

Issued at 220 PM CDT Sat Sep 5 2026

Currently the western half of the CONUS is under southwest flow thanks to a large area of low pressure/heights in the Pacific Northwest. The ridge axis is roughly north/south over western Minnesota. At the surface a weak low pressure sits in southwestern North Dakota with a warm front across the South Dakota border. Lingering storms from a low level jet (LLJ) this morning still continue in far north central ND. These storms produced heavy rain with very little storm motion, so several Flood Advisories were issued. The latest one will expire at 1930z. There are some bubbling cumulus clouds, elevated, in the south central that have some light radar returns with them. According to our 18z sounding, there is a heavy capping layer, then plenty of elevated CAPE.

The rest of today should be mostly quiet storm-wise as the surface low pressure slides to the east, and there are currently no shortwave in the southwest flow. Most CAMs have no storms in the area until the LLJ kicks back in after 04z. There is still a level 1 risk for the eastern 2/3rds of the state for today, although the next round may not be until after sunset again or until Sunday. Today will also be very warm with highs in the mid 90s, that is roughly 20 degrees above normal. These hot temperatures will continue through Monday, although Monday will be in the 80s.

The severe thunderstorm risk will continue all holiday weekend with a level 1 risk through Monday as the southwest flow and warm temperatures continue. Sunday the surface low looks to be in northeastern South Dakota with an area of 2000-4000 J/kg of MUCAPE over North Dakota wrapping around the low. The shear will be marginal with around 15kts in the east and 35kts in the west. Most CAMs do not have much going on until after sunset again when a possible LLJ and kick storms off using that elevated MUCAPE. The area of concerned would be around Highway 2 between 6pm and midnight. Sunday night a strong area of diffluence will also be over the state starting around 1am, so there will likely be overnight storms.

Labor Day a Northern Rockies low pressure will swing up to the Northern Plains into eastern Montana. With this, possibly a widespread rain event could occur through the first half of the day before North Dakota gets into the dry slot of the low. Models have a much smaller area of severe weather, with a skinny area of MUCAPE around 2000 J/kg in western ND. Shear will be plenty however 40-55kts. A limitation for storms is a strong warm layer at 850mb that will be a capping layer. CAMs otherwise have a line of storms coming out of Montana in the morning off the front.

The rest of the forecast will be a slow cooling trend with cooler air wrapping into the northern Plains. As of now forecast temperatures will reach the 60s and 70s by next Saturday. Next week will also be breezy to windy, especially Tuesday and Wednesday where an Advisory or High Wind Warning may be needed.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 157 AM CDT Sun Sep 6 2026

Chances for showers and thunderstorms will gradually increase through the forecast period. Forecast confidence is high enough to include PROB30 mentions at KXWA late Sunday morning through mid afternoon, KMOT during the afternoon, and KJMS during the late afternoon and evening. But the chance for a shower or storm near any terminal at any given time beyond the first few hours of the forecast period is greater than zero. A few strong to severe storms are possible from Sunday afternoon onward, capable of large hail and strong, erratic wind gusts. IFR visibility from heavy rain and brief MVFR ceilings are also possible with heavier showers and any thunderstorm. Outside of showers and storms, there is a low chance of fog and/or very low ceilings developing from around KMOT to KJMS early Sunday morning. Otherwise, VFR conditions are likely to prevail. Winds will primarily be easterly to southerly, increasing to around 10-15 kts on Sunday.

BIS WATCHES/WARNINGS/ADVISORIES

None.