textproduct: Bismarck

KEY MESSAGES

- Isolated to scattered showers and a few thunderstorms are expected tonight.

- Additional isolated to scattered strong to severe storms are forecast for Saturday and Sunday.

- Near to slightly above average temperatures will persist through late next week.

- Breezy to windy conditions combined with lower humidity values may bring increased fire weather concerns on Monday.

UPDATE

Issued at 1245 AM CDT Sat Aug 29 2026

A conditional risk for isolated severe thunderstorms remains through tonight, although the overall threat remains low. High amounts of elevated CAPE will remain through the night, with perhaps some lessoning of the cap in the mixing layer. Shear will also remain modest through the night especially in the south. The limiting factor is lift needed to initial stronger thunderstorms. A decent low level jet looks to setting up to our east, which is starting to develop thunderstorms in SD and far eastern ND. These could be the areas to monitor through the night, although perhaps outflow or boundaries from these storms may be enough to kick off a stronger storm in the CWA. Thus only made minor PoP changes based on current trends for this update.

UPDATE Issued at 929 PM CDT Fri Aug 28 2026

No lightning strikes have been observed across the CWA in the past 45 minutes or so, though scattered showers remain present over parts of western and south central North Dakota. These are expected to continue through the night, though a few isolated thunderstorms could return. With thunderstorms failing to organize earlier this evening, the probability for severe weather is decreasing across the forecast area overnight, though remains greater than zero. If any severe weather manages to develop tonight, it will most likely be off a strengthening LLJ and would mostly impact the James River Valley before moving eastward relatively quickly.

UPDATE Issued at 646 PM CDT Fri Aug 28 2026

A few showers and thunderstorms have developed in southwestern North Dakota where skies were mostly clear until about an hour or so ago. However, incoming clouds have rapidly overtaken clear skies and seem to be helping inhibit most organized convection at this time. A lack of shear has also helped limit storm development. As storms progress eastward, they should begin to enter a higher shear environment. However, there is some question as to whether or not relatively weak forcing will be able to tap further into modest elevated instability as the sun sets and surface CIN continues to increase.

DISCUSSION

Issued at 120 PM CDT Fri Aug 28 2026

Early this afternoon, a subtle shortwave upper trough was rounding the northern periphery of a mid/upper ridge centered over the southern Rockies and High Plains. An attendant band of mid-level WAA is aiding in the persistence of showers and thunderstorms from southwest Manitoba to northeast South Dakota. This activity is still forecast to be placed across eastern North Dakota later this afternoon and evening. An axis of modest instability (around 500- 1000 J/kg MUCAPE) and sufficient effective shear (around 30-40 knots) will continue to support the potential for occasional and isolated instances of hail around pennies to quarters in association with this elevated convection. Also later this afternoon, another subtle shortwave trough will translate eastward across southern Montana with a jet max nosing into western South Dakota. Despite ample convective inhibition, CAMs are insistent that convection will develop ahead of this wave given robust synoptic ascent. However, this activity will likely struggle given the aforementioned CIN, and it's possible only a very small window exists for the potential of severe weather across southern North Dakota during peak diurnal heating late this afternoon. Therefore, if a storm can develop during the time of minimum CIN and can remain discrete, there is a chance this hypothetical storm could produce quarter to golfball size hail along with up to 60 mph wind gusts. Most likely though, much of the activity today will struggle which is largely the reason SPC has maintain a marginal (1/5) risk for severe weather for today and tonight.

Very late tonight into Saturday morning, short range guidance is hinting at the potential for a loosely organized backwards propagating MCS across southeastern North Dakota. This could potentially impact portions of the area from Jamestown to Oakes; however much of this activity should remain just east of the area, especially given that the LLJ will have veered out and is forecast to nose into central Minnesota by daybreak Saturday morning. Most of Saturday will end up on the quieter side with afternoon highs generally a tick above average in the mid to upper 80s. Another subtle shortwave is forecast to round the northern periphery of a strong mid/upper ridge (generally centered over the central and southern plains), and will be the primary catalyst for another round of thunderstorms Saturday evening and night. Generally speaking, sufficient instability and shear should be in place across the southern half of North Dakota to support strong to severe storms capable of large hail and damaging winds. It's possible a messy storm mode could limit the large hail threat to an extent; however, DCAPE in the neighborhood of 750-1000 J/kg could support some localized downbursts with up to 60 mph wind gusts possible. With the loss of diurnal heating Saturday eve/night, the intensity of thunderstorm activity should gradually decrease. That being said, convective inhibition after sunset should be fairly weak, and continued broad ascent from a train of perturbations embedded in southwesterly flow aloft should continue to support sub-severe shower and thunderstorm activity well into the overnight hours.

It's a little unclear exactly how activity on Sunday will evolve. Mid-range guidance appears fairly confident showers and storms will be ongoing through much of the first half of Sunday across a large portion of the state well out ahead of a the primary trough axis. Given this, it's a bit difficult to pin point whether or not the atmosphere will destabilize enough before the main trough ejects out across the northern plains and southern Manitoba. This potential atmospheric destabilization will be key to whether or not widespread strong to severe storms develop across western and central North Dakota Sunday afternoon and evening. Given this level of uncertainty, SPC elected to go with a marginal (1/5) risk of severe weather on Sunday. Details should become clearer over the next couple of days. Regardless of what occurs on Sunday, a weak cold front is forecast to sweep across the state Sunday night. This will generally lead to temperatures returning to near average for the beginning of next week. Also, guidance appears to be in good agreement that a strong surface low across southern Saskatchewan will result in a tight pressure gradient across the northern half of the state on Monday. Currently, forecast max wind gusts Monday afternoon are hovering around 35 to 45 mph. However, model soundings indicate deep mixing and uniform flow in the boundary layer which could allow for locally higher gusts from time to time. Additionally, lower RH across the western portions of the state together with the windy conditions could present some fire weather concerns. The parade of upper troughs is likely to return by Tuesday and persist through the end of the work week next week. Thus, periodic chances for showers and storms Tuesday through Friday have been maintained in this forecast package.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1245 AM CDT Sat Aug 29 2026

Overall VFR conditions are expected through the forecast period. Showers and thunderstorms could brief MVFR conditions at times through the forecast period. Tonight isolated showers and thunderstorm chances will push from central to east. Some PROB30 groups were used to account for this, although the overall chances for precipitation is low. Another round of showers and thunderstorms are then possible later Saturday through Saturday evening. Confidence in these are also low to moderate, thus used PROB30 groups for sites with moderate chances. Look for light and variable winds tonight becoming a light easterly wind on Saturday.

BIS WATCHES/WARNINGS/ADVISORIES

None.