textproduct: Bismarck

KEY MESSAGES

- Scattered to numerous severe thunderstorms over much of western and central North Dakota late this afternoon and tonight.

- There is a Marginal Risk (threat level 1 of 5) of severe thunderstorms over portions of western North Dakota Monday night.

- Another round of scattered to numerous severe thunderstorms is possible on Tuesday.

- Above normal temperatures through Tuesday, then trending cooler for the remainder of the week.

UPDATE

Issued at 826 PM CDT Sun Jun 7 2026

** Mesoscale Discussion **

The peak intensity of this severe thunderstorm even is beginning and is expected to be maximized through about 10 pm CDT/9 pm MDT. A severe-storm risk will linger thereafter, but the peak of the event is expected in the next two hours.

As of 01z, multiple linear convective segments are evolving in western ND, with one prominent and developing bowing segment in southwest ND from near Belfield to Mott, Hettinger, and south to near Bison, SD. The environment downstream of this developing bow echo is characterized by moderate to strong bouyancy and sufficient low- and midlevel wind shear to support damaging to destructive winds downstream in southwest and parts of south central ND. WoFS guidance continues to support this corridor as having the highest probability of damaging winds, particularly in parts of Dunn, Stark, Hettinger, Adams, western Sioux, Grant, western Morton, Oliver, and Mercer Counties through 10 pm CDT.

The storms in northwestern ND, extending southward into the west end of Lake Sakakawea, have begun to take on a more organized and linear appearance in the last 30 minutes as well. These storms are also in a sufficient CAPE-shear setting to support both large hail and damaging winds.

The 00z Bismarck sounding displayed steep lapse rates and large MLCAPE, but week deep-layer shear, as long-forecast by guidance. While middle and upper-level winds are forecast to increase in time, the developing QLCS is apt to outpace the stronger flow aloft by late evening. Once that occurs and the QLCS moves into weaker low- and deep-layer shear, roughly along and east of the Highway 83 corridor, it may become outflow dominant and the magnitude of damaging winds is apt to gradually decrease. WoFS guidance supports this evolution as well, with peak gusts mainly in the 55 to 65 mph range once the storms pass roughly east of the Highway 83 corridor.

CJS

UPDATE Issued at 616 PM CDT Sun Jun 7 2026

** Mesoscale Discussion **

The severe storm risk is rapidly increasing in western North Dakota, including initially the potential for large to very large hail of 1.5 to 2.5 inches in diameter. The potential for damaging to destructive straight-line winds will also increase the next few hours, with the previously-advertised corridor of peak gusts of 85 to 100 mph still in the forecast.

As of 23z, supercells have formed along the surface front and wind shift in western ND, notably in southern McKenzie and Golden Valley Counties. These supercells have formed in an environment characterized by strong bouyancy with MLCAPE on the order of 3000 J/kg and effective-layer shear around 50 kt, which is favorable for large to very large hail. Hodographs do display a relatively straight geometry in this area, suggesting cells may continue to undergo splitting and merging in this area. Right-moving supercells are slightly favored over left-moving supercells in this region given modest low-level curvature in the hodographs. Eventually, if sufficient mergers and clustering occurs, the dominant hazard with these initial supercells may also become more damaging-wind-related. Recent WoFS cycles do suggest these supercells may indeed merge and begin propagating downstream toward the west end of Lake Sakakawea in the next few hours, favoring that increase in damaging winds.

Low-level convergence along the wind shift further north in western Mountrail and Burke Counties and vicinity appears to be weaker, and visible satellite imagery suggests fewer attempts at deep convective initiation in that part of northwestern North Dakota at this time. Nonetheless, a low to medium probability of a supercell or two forming in northwest ND continues.

Upstream supercells in southeastern Montana are in a favorable CAPE-shear setting for continued maintenance, and their motion is expected to continue taking them near the frontal zone and into southwestern North Dakota in the next few hours. We expect that once significant upscale growth begins, and a potential bow echo takes shape from these storms, that they will begin to take a more north-northeast forward motion (following forecast Corfidi vectors) rather than the east-northeast motion that the right- moving supercell motion vectors have favored thus far. As a result, even the supercell in far southeast Carter County, MT, and northwestern Butte County, SD, may become part of a larger bowing complex that moves into southwest and south central ND. WoFS runs continue to signal potential for high-end wind gusts with these expected bowing structures in the coming hours.

CJS

UPDATE Issued at 409 PM CDT Sun Jun 7 2026

Quick update for issuance of Severe Thunderstorm Watch number 285 for western and much of central North Dakota. The Storm Prediction Center has opted for a PDS (Particularly Dangerous Situation) Severe watch due to the likelihood of damaging winds this evening.

DISCUSSION

Issued at 325 PM CDT Sun Jun 7 2026

Currently, southwest flow aloft ahead of a dynamic upper level trough advancing east into the Rockies. Quasi-stationary/slowly east moving surface trough/frontal boundary stretches from far western South Dakota north-northeast across far western North Dakota this afternoon. Very warm and humid weather across western and central ND, with current afternoon temperatures well into the 80s to lower 90s, along with sfc dewpoint temperatures in the 60s to near 70. This results in mixed layer CAPE of 2-3K J/KG west into north central. Effective/bulk shear remains mainly along to west of the sfc boundary, 35-50kts far west. Elevated echos over central ND at the moment, and not expecting anything from this with a stout low level capping inversion here.

Some storms may initiate between 20-22Z across the western Dakotas looking at the latest CAMs/WoFS runs, with some models closer to 23Z. Have not seen anything out of the Black Hills yet, but there have been a few towers and orphan anvils there the past hour. Nothing within the CU field over western ND, but latest mesoanalysis indicates CIN eroding. Anything developing across western ND would be discrete and would pose a threat for very large hail considering the lapse rates we've sampled via the BIS 18Z sounding. Will be monitoring this area closely. A bigger threat for severe winds will materialize as convection developing over the higher terrain of the Big Horns and southeastern Montana push northeast and congeals into a linear line/bow echo. Last several WoFS runs are indicating a damaging wind swath from southwest North Dakota northeast into north central areas of North Dakota, including Beach and Bowman, northeast through Dickinson, Killdeer, Hazen, Garrison, and possibly Minot. Winds of 85-100 mph will be possible in this swath. Latest SPC Day 1 did upgrade this area to a Moderate Risk (level 4 of 5) with elevated likelihood of occurrence, with much of the remaining area outside of the James Valley still in the Enhanced Risk (level 3 of 5) area.

Storms will end west to east tonight behind the FROPA, with winds becoming more west/northwest and clouds diminishing. Cooler and less humid for Monday behind the front.

WAA and southwest flow aloft increases Monday night into Tuesday, as a subtle mid level S/WV ridge moves across the area ahead of another mid level trough. Marginal (threat level 1 of 5) Risk for severe storms over western North Dakota Monday night as lead energy ejects out of the trough and low level moisture increases again, followed by another Slight/Enhanced Risk (2/3 of 5) for much of the area on Tuesday as the aforementioned trough pushes into the Northern Plains and drives another frontal boundary east across the region.

Afterwards, we will remain in an active pattern with the general flow dominated by upper level lows or troughing. This will maintain daily chances for showers and thunderstorms, along with temperatures trending cooler and closer to early/mid June highs and lows (highs mid 60s to mid 70s...lows 45-55).

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 646 PM CDT Sun Jun 7 2026

Thunderstorms have initiated between KXWA and KDIK and will continue to expand into a strong line that will sweep east across the state overnight. The main aviation challenge is timing the arrival/departure of this line of thunderstorms. KXWA and KDIK will likely have thunderstorms within the 10 mile vicinity within an hour (00Z-01Z). Arrival at KMOT is most likely around 02Z-03Z. KBIS may be more around 03-04Z for arrival. Timing is a little more challenging for KJMS but arrival will likely be after 05Z. Strong wind gusts over 40 to 45 kts is expected and can not rule out a few severe wind gusts over 50 kts within the strongest line segments.

The wind will turn from southerly ahead of the storms to west northwesterly behind the thunderstorm gust front.

We will also have to watch for lower ceilings within the heavy rain, and also towards morning across our southeastern counties. IFR ceilings are expected at KJMS around dawn and could persist for several hours before scattering out.

BIS WATCHES/WARNINGS/ADVISORIES

None.