textproduct: Bismarck

KEY MESSAGES

- Moderate to high chances for showers and thunderstorms will remain tonight through Labor Day. Isolated to scattered severe thunderstorms are possible.

- Unseasonably warm and humid through the Labor Day, then trending cooler.

- Windy on Tuesday, with near-critical to critical fire weather conditions across southwest and south central North Dakota.

DISCUSSION

Issued at 332 PM CDT Sun Sep 6 2026

A general unsettled pattern to bring isolated to scattered thunderstorms, possibly severe, through tonight. High amounts of instability, mostly elevated, will continue through tonight. Meanwhile a weak pseudo warm front near a developing low will be draped across much of the state through tonight. Aloft sees falling heights as the upper level ridge moves east and southwest flow takes its place. Models also indicate a low level jet may return this evening through tonight. All this combined will return widespread chances for showers and thunderstorms through tonight. Today's storms have left plenty of remnant boundaries across the state, How these interact with each other could influence severe weather tonight as well. Overall the stronger severe weather will be located to anywhere with higher shear which currently analyzed in the north and west. Elsewhere has less shear, although high amounts of instability may be just enough for stronger pulse like storms. Overall a hail threat up to golf ball size will be possible with any stronger storm through tonight, with rotating storms in the higher sheared areas having the better potential for the bigger hail. The wind threat is modest through tonight. DCAPE is high, although 0 to 3 km shear is lacking as are low level lapse rates. Thus winds 60 to perhaps 70 mph are possible. There still remains a low tornado threat through tonight. This is highly dependent on boundary interactions, although there is some increased SRH and 0 to 1 KM shear through tonight. Of note are some increased non supercell parameters through this evening. Overall confidence in surface based storms through tonight is low, yet a tornado is possible along any boundary interactions. High pwats over 1.5 inches will continue to bring a heavy rain and localized flooding threat. If confidence in any one area for heavy rain increase then perhaps a flood watch may be needed tonight and perhaps again on Monday. Otherwise look for mild lows in the 60s tonight. Patchy fog may also return tonight to areas without thunderstorms and some clearing. Confidence was not high enough to include fog at this time.

Surface low then moves across the state on Labor Day bringing more isolated to scattered severe thunderstorms. Timing wise, severe storms could be ongoing in the morning as a low level jet continues ahead of the low in the morning. As the low pushes through following by a cold front, thunderstorms could continue through the day from west to east through the day. A few thunderstorms could then develop along a trailing front tomorrow evening, although this may be more uncertain depending how much the daytime convection impacts the atmosphere. All hazards remain possible. Increased shear and instability will support large hail to golf ball sized. Meanwhile, the potential for line development could bring strong winds to 70 mph. There also remains a conditional tornado threat for Monday as dewpoints remain high and a weak warm front lifts ahead of the low. Storms would have to be surface based to increase the tornado threat. Currently SPC has a Marginal Risk for severe weather. CSU-MLP severe outlooks shown all threats possible for Monday. Thus anyone with outdoor plans for Monday should continue to be weather aware on Monday. Highs for Labor Day will continue to be warm with 80s for most of the area, and 70s north. Breezy southerly winds will be found until a breezy westerly wind moves in behind the low. Precipitation diminishes Monday night, with lows cooling in the 50s to near 60.

The main concern for Tuesday remains strong winds. Both the NBM and ECMWF EFI support advisory criteria winds of sustained speeds between 30 and 40 mph and gusts of 45 to 55 mph. Tuesday will be much cooler with highs from the upper 60s northwest to lower 80s southeast, but also drier with minimum humidity falling to around 25 to 35 percent. The combination of strong winds and lower RH will likely bring near- critical to critical fire weather conditions to all of southwest and some south central North Dakota, with critical conditions especially possible in the far southwest where RH could fall closer to 20 to 25 percent. A few showers may also be found Tuesday, mainly in the north. Cooler temperatures remain in the forecast on Wednesday, but with winds not nearly as strong yet still breezy at times. Ensembles have now trended toward a quick warmup on Thursday due to a transient ridge, followed by a distinct cooling trend heading into next weekend, but with increasing spread due to synoptic scale wave phasing uncertainty. There could be an increased fire weather threat on Thursday, especially in the southwest. Limited chances for precipitation also look to be Wednesday through Friday.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 115 PM CDT Sun Sep 6 2026

Showers and thunderstorms to bring periods of MVFR to brief IFR conditions at times throughout the forecast period. Showers and thunderstorms will be possible across most TAF sites this afternoon then again later today through tonight and possibly into Labor Day. Any storm that develops could bring gusty winds, hail, and MVFR to brief IFR conditions. Otherwise look for VFR conditions, with some low MVFR to perhaps IFR ceilings at times. Patchy fog could return tonight into Labor Day morning, although confidence was not high enough to include at this time. A breezy south southeast wind may also be found throughout the forecast period, with variable winds during thunderstorm passage.

BIS WATCHES/WARNINGS/ADVISORIES

None.