textproduct: Bismarck

KEY MESSAGES

- Numerous severe thunderstorms are expected this afternoon and evening. Potential exists for significant hazards, including hail up to tennis ball size, damaging winds up to 80 mph, and a few tornadoes, one or two of which could be strong.

- 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 903 AM CDT Tue Jun 9 2026

Scattered showers and a few thunderstorms continue over northwestern North Dakota, while isolated showers with a few rumbles of thunder have also developed over the southwest. There have been a few enhanced radar echoes in the far northwest, though based on dual-pol radar data, these were/are likely brief heavy rain mixed with small hail. Adjusted PoPs over the next few hours based on the latest radar trends.

UPDATE Issued at 704 AM CDT Tue Jun 9 2026

No significant forecast changes are needed with this update. Scattered showers and isolated thunderstorms have developed as anticipated in northwest North Dakota.

DISCUSSION

Issued at 412 AM CDT Tue Jun 9 2026

Early morning water vapor imagery and upper air analysis show a trough digging into the Northern Rockies, with lee surface cyclogenesis underway near the Bighorn Mountains. A responding low- level jet is strengthening along the MT/ND, providing warm- air advection and moisture transport. CAMs have been indicating some elevated convection initiating in northeast Montana and northwest North Dakota by sunrise, and this is already underway. MUCAPE around 500-1000 J/kg and effective bulk shear around 20-30 kts could support a few stronger updrafts, but confidence is low on whether any air parcels/inflow will be able to realize the maximum CAPE/shear potential. We are not anticipating any severe weather this morning, though in a worst-case scenario, a stronger storm could produce hail up to the size of pennies or nickels.

The deepening upstream trough will push mid level height falls into western North Dakota this afternoon, with the lee surface trough also sliding in underneath. Strong southerly surface flow downstream of the surface trough will advect 60s F dewpoints poleward by early to mid afternoon as temperatures rise into the mid 80s to mid 90s, yielding strong to extreme buoyancy on the order of 3000-4000 J/kg MLCAPE. By late afternoon, models project the formation of a triple point surface low over west- central North Dakota as mid to upper level wind speed and DCVA begin to increase, pushing 0-6 km shear into the 40-50 kt range. The warm/moist sector is likely to remain capped through mid afternoon, but surface heating, mid level cooling, and strong synoptic scale forcing should all be sufficient to erode or overcome CIN by late afternoon. This all sets the stage for what could be a significant severe thunderstorm event/outbreak, with all hazards possible but strongly regulated by storm mode.

CAMs are in strong agreement that convective initiation will occur along the surface trough/dryline axis around 3 to 4 PM CDT. Initial storm mode is favored to be discrete, but shear vectors are forecast to quickly turn more parallel to the surface trough/dryline, which could cause a quick transition to a linear mode. Any discrete storm will be capable of very large hail given the CAPE/shear parameter space. The only two apparent limiting factors that could keep hail from becoming more destructive (baseball size or larger) are stronger low level shear and a shorter duration for a discrete storm mode. This leaves our most likely maximum hail size forecast at tennis balls. While any discrete supercells will be capable of producing damaging winds in their rear-flank downdrafts, a more significant, widespread damaging wind threat could emerge once storms congeal into a forward-propagating QLCS. All requisite environmental parameters for damaging winds up to 80 mph are forecast to be present, including 0-3 km shear as high as 40 kts.

A tornado risk exists for both discrete and linear storm modes. All forecast parameters for a mean environment of tornadoes in North Dakota are easily met or exceeded, but with some spatiotemporal limitations. Most concerning are forecast hodographs across the entire warm/moist sector, which show strong clockwise curvature in the lowest 1-2 km AGL with strong streamwise vorticity ingestion for right-moving supercells. What could limit the tornado threat, both in terms of numbers and intensity, is that the strongest low level shear/SRH is forecast in the evening, by which time storm mode is favored to be linear. But that does not preclude the potential for line- embedded mesovortices producing shorter-lived tornadoes. Given the shorter window for a discrete mode concurrent with a relatively less favorable environment for tornadogenesis, we will maintain our messaging of a few tornadoes, with one or two possibly strong (EF2 or greater). But this aspect of the forecast will need close monitoring and evaluation throughout the day, as "a few" may be underselling the threat ceiling.

The QLCS is forecast to exit into eastern North Dakota late this evening. Additional shortwave energy ejecting from the base of the upstream trough could return showers and isolated thunderstorms to western and central North Dakota late tonight into Wednesday morning. The threat for severe weather over this time period is very low, but there could be residual MUCAPE as high as 500 J/kg with effective bulk shear as high as 50 kts (using the 2-7 km layer as a proxy). The rest of Wednesday looks to be cooler and windy, with a low chance of diurnally driven showers or thunderstorms. A potent shortwave is forecast to enter the upstream trough and blast through the Northern Plains Wednesday night into Thursday, over which the NBM has increased precipitation chances to around 60 to 80 percent. Longer-range ensemble guidance favors a cyclonic northwest or quasi- zonal flow persisting through the weekend and into early next week. This keeps near-daily low to medium chances for showers and thunderstorms in the forecast, but the probability for severe weather from Wednesday onward is very low. Below normal temperatures are also favored over this time period, with highs mostly in the 60s to mid 70s and lows mostly in the 40s to lower 50s.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 704 AM CDT Tue Jun 9 2026

Low ceilings have developed across southern North Dakota early this morning. Forecast confidence in their evolution is low, including how far northward they may spread. The low clouds are likely to scatter by the afternoon. Scattered showers and isolated thunderstorms will move across northwest North Dakota this morning, possibly approaching KXWA. South-southeast winds are forecast to increase to around 15-25 kts later this morning and afternoon, with gusts to 25-35 kts.

Numerous severe thunderstorms are expected to develop in western North Dakota by late afternoon, moving through central North Dakota this evening. Very large hail is possible with individual storms, and +50 kt gusts can be expected with lines of storms. Heavy rain with storms will reduce visibility to IFR/LIFR at times. For this set of TAFs, maintained PROB30 mentions at KXWA and KDIK, and prevailing/TEMPO groups at KBIS, KMOT, and KJMS.

BIS WATCHES/WARNINGS/ADVISORIES

None.