textproduct: Bismarck

KEY MESSAGES

- Isolated to scattered showers and storms will continue this afternoon through tonight. A strong to severe storm cannot be ruled out, especially this evening.

- 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.

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 /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1231 PM CDT Fri Aug 28 2026

Mainly VFR conditions expected through the 18Z period. Two rounds of showers and thunderstorms possible through the forecast period. The first is ongoing as a broken line of showers and thunderstorms moves from central to east. This will mainly impact KJMS for another couple of hours, through 19-20Z this afternoon. The second being this evening which only had enough confidence for PROB30 groups in western and some central sites. Any thunderstorm could bring brief MVFR conditions. An isolated severe storm is also possible with this second round of storms tonight, with large hail and damaging winds the main threats. Otherwise, a steady south/southeasterly wind from 10 to 20 knots with a few higher gusts for most sites today, diminishing to mainly light and variable tonight.

BIS WATCHES/WARNINGS/ADVISORIES

None.