textproduct: Bismarck

KEY MESSAGES

- Severe thunderstorms producing damaging winds up to 70 mph will exit the James River Valley after 1 AM CDT.

- Warm, humid, and windy today. Then cooler with near-daily shower and thunderstorm chances through the rest of this week and into early next week.

UPDATE

Issued at 1218 AM CDT Wed Jun 10 2026

The Tornado Watch was allowed to expire on time. However, the line of storms has significantly strengthened over the last hour as it has entered a more unstable air mass. Gusts to around 70 mph have been reported near Jamestown and Ellendale, and quarter size hail was also reported in Jamestown. These storms will exit our forecast area by around 1 AM CDT, so have opted to not extend the Tornado Watch.

UPDATE Issued at 935 PM CDT Tue Jun 9 2026

Severe threat continues more or less along and east of the Highway 3 corridor where very strong instability remains in place. As the evening continues, the tornadic threat will continue to diminish, but now that the line has filled in from north to south, strong winds, with possibly a few large hail instances remain the greatest concern as it surges east.

UPDATE Issued at 648 PM CDT Tue Jun 9 2026

Severe risk remains elevated over northwest and central North Dakota, where Tornado Watch continues. Did end up trimming off a few counties in the southwest (Stark southward) where boundary has passed into and temperature/dewpoint continue to drop off. In the area still under the watch, very strong instability remains in place, particularly over north central North Dakota dipping a bit into south central where CAPE values of around 3000-4000 J/Kg are noted.

DISCUSSION

Issued at 237 PM CDT Tue Jun 9 2026

Numerous severe thunderstorms remain the expectation for this afternoon and evening with all threats on the table.

Currently, elongated low pressure is analyzed over the western Dakotas. Potent shortwave energy is in the process of lifting up through the Northern Plains, while previously stationary surface frontal boundary has lifted northward into Canada as a warm frontal boundary. This warm frontal boundary has advected very warm and moist air into the state. North to south orientated cold frontal boundary off said low will rapidly slide west to east across the state this afternoon and evening. This will force widespread thunderstorm activity with numerous severe thunderstorms likely.

One of the biggest questions remains in regard to storm mode. With the cold fropa, normally a more linear mode would be favored. However, with 0 to 6 km bulk shear favoring a 45 degree angle in relation to the front, it seems a more clustered mode is likely. What may wind up happening in the end is a line of embedded supercells develops. Especially as it heads east towards an even more favored severe weather environment. Therefore, the current thinking is that discrete cells may develop in western North Dakota by mid-afternoon. These will likely transition into some form of line with the question being whether it's a more traditional QLCS, or a line of embedded supercells. Should the latter wind up being the case, then a tornado and large hail threat would persist longer than otherwise would be anticipated. Besides storm mode, curved hodographs are highly favorable towards tornado genesis for any discrete cells and within any QLCS. As such, believe the SPC hatched 10 percent tornado outlook is reasonable, though the highest SigTOR parameter highlights northern ND during the middle of the afternoon and eastern, especially northeastern, ND late this afternoon and evening.

Once the main line passes through, isolated to scattered showers and a few sub-severe thunderstorms are possible through Wednesday morning. After which, mostly dry conditions are expected during the afternoon and evening. Additional showers and thunderstorms are then possible from west to east late Wednesday night through Thursday as another shortwave off upper Canadian low passes through. These thunderstorms are expected to remain sub-severe at this time. A few occasional showers and thunderstorms are then periodically possible through the remainder of the week.

Much cooler temperatures are expected beyond today through the remainder of the week with highs mostly in the 60s and 70s. Simultaneously, lows will also be in the 40s for most locations, most nights beyond tonight. Breezy to windy conditions are also on tap for most days to finish out the week.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1218 AM CDT Wed Jun 10 2026

The threat for severe thunderstorms will soon be exiting KJMS and surrounding areas. VFR conditions are otherwise anticipated through the forecast period, although some lower ceilings could enter northwest North Dakota late Wednesday evening. Isolated to widely scattered showers and thunderstorms could return to western and central North Dakota Wednesday morning and afternoon, but the probability of impacts to aviation remains low at this time. Westerly winds around 10-15 kts overnight will increase to 20-25 kts Wednesday afternoon.

BIS WATCHES/WARNINGS/ADVISORIES

None.