textproduct: Bismarck

KEY MESSAGES

- Low to medium chances for thunderstorms tonight. A few storms could become strong, mainly in southwest North Dakota.

- Numerous severe thunderstorms are possible late Saturday afternoon through Saturday night. Expected hazards include hail up to 2 inches in diameter and damaging winds up to 70 mph, with a tornado possible.

- Additional isolated to scattered severe thunderstorms are possible Sunday through Monday.

- Near to above normal temperatures are favored this weekend through the middle of next week, warming to well above normal heading into the Forth of July holiday weekend.

DISCUSSION

Issued at 346 PM CDT Fri Jun 26 2026

A weak mid level shortwave is lifting northeastward through the eastern half of the state this afternoon. Isolated to widely scattered showers and thunderstorms remain possible through the afternoon from the Turtle Mountains through the James River Valley. CAPE and shear are not forecast to become sufficient to support stronger convection.

An upper level ridge is forecast to move over western North Dakota tonight, but it could be undercut by mid level southwest flow with embedded shortwave energy. One to several clusters of thunderstorms are likely to develop near the mountains of central Montana this evening and quickly move eastward toward western North Dakota by around midnight. Some CAMs maintain stronger convection in southwest North Dakota late tonight as both MUCAPE and effective bulk shear increase in response to a strengthening low level jet. The intensity of convection will ultimately be dictated by the CAPE/shear parameter space of the elevated inflow layer, which may not necessarily be the most unstable layer. Nevertheless, there is a low probability for a marginally severe thunderstorm in southwest North Dakota late tonight, with no greater than baseline hazards expected (quarter size hail and/or 60 mph wind gusts). Scattered showers and thunderstorms may continue to propagate northeastward through the night into Saturday morning as the low level jet slides eastward.

Persistent southerly flow ahead of a lee surface trough will promote strong moisture transport on Saturday, but mid level capping is likely to prevent surface-based convection prior to late afternoon. Surface winds could approach advisory criteria across all but far western North Dakota Saturday afternoon, with sustained speeds around 20 to 30 mph and gusts to near 45 mph. It will also be warmer and more humid for most areas, with dewpoints in the 60s and highs around 90 in the southwest, the mid to upper 70s far north, and 80s in between.

By late Saturday afternoon, the lee surface trough is forecast to lie along the ND/MT border, with a potential triple point axis somewhere between Glendive and Williston. Mid level height falls should be spreading into western North Dakota at this time, and an upper level jet streak is also forecast to be pointed toward the Black Hills, placing its left exit region over the lee surface trough. All this combined with strong diurnal heating should sufficiently erode capping to initiate convection in western North Dakota between 5 and 7 PM CDT. Shear vector orientation to surface boundaries tends to favor an initial discrete mode both along the west-to-east warm front across northern North Dakota and along the north-to-south lee trough, although deep-layer mean wind vectors are more parallel to the lee trough which could anchor updrafts to that boundary and cause quicker upscale growth. For any discrete storms, 3000 J/kg CAPE and 0-6 km shear increasing to 40-50 kts through early evening will support very large hail. Because of the potential for mid level dry air entrainment and stronger low level shear/SR inflow, we have limited our most likely maximum hail size forecast to 2 inches in diameter for now. There is at least some risk for a tornado, especially in northwest North Dakota where a more due easterly low-level/surface flow is forecast. Here, the HREF advertises 0-1 km SRH increasing over 100 m^2/s^2 by early evening, with STP in the 1-2 range. There could also be a narrow window in both time and space for a tornado threat to extend southward along the lee trough if storms are able to remain discrete. The HREF shows this potential to be along and west of Highway 83 from around 8 to 10 PM CDT. But latest CAM guidance does tend to favor a quicker transition to a cluster or linear mode on account of increasing synoptic scale forcing and cold pool conglomeration as convection spreads into central North Dakota heading into the overnight hours. Once this occurs, the dominant hazard will transition to damaging winds, which could be widespread and significant. Most, if not all requisite ingredients for +80 mph winds appear to be in place. There is still just enough forecast uncertainty in finer-scale details to limit the most likely maximum wind gust potential to 70 mph in our messaging, but an increase to 80 mph may be needed with future forecast updates. While the tornado threat would be relatively lower with a QLCS than with discrete supercells, it would still be greater than zero.

After the severe threat ends late Saturday night (or perhaps early Sunday morning) there is uncertainty in a conditional severe threat on Sunday which could be heavily influenced by how the post-MCS environment evolves. There is high confidence in strong deep layer shear on Sunday, but lower confidence in forcing, the westward extent of moisture/buoyancy, and CIN. This conditional severe threat now appears to extend through Sunday night and into Monday as an upper level low deepens between the Northern Rockies and Northern Plains, but there is some ensemble spread in its evolution. Beyond Monday, ensembles broadly favor a southwest flow pattern prevailing through the end of next week, with temperatures trending above normal. After a break on Tuesday, daily chances for showers and thunderstorms, some strong to severe, resume for the second half of next week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 111 PM CDT Fri Jun 26 2026

A large area of stratus with MVFR to low VFR ceilings covers much of western and southern North Dakota early this afternoon. Forecast confidence in the evolution of the stratus is not high, but the general expectation is that it should slowly migrate northeastward through the day and into the evening, with VFR becoming more common than MVFR. From tonight into Saturday morning, widespread MVFR/IFR ceilings are forecast to develop, beginning in northwest and north central North Dakota, then expanding southward.

Scattered showers will remain possible from near KBIS to KJMS this afternoon, with no impacts to aviation expected. Isolated thunderstorms are also possible to the north and east of KMOT. Later this evening through tonight, a cluster of thunderstorms could enter southwest North Dakota with strong and erratic wind gusts, and perhaps some small hail. These showers and storms could spread into northwest and central North Dakota later tonight into Saturday morning.

Southeast to easterly winds around 10-20 kts are expected through the forecast period, becoming stronger by Saturday afternoon. Low level wind shear could impact KDIK and surrounding areas late tonight into early Saturday morning

BIS WATCHES/WARNINGS/ADVISORIES

None.