textproduct: Bismarck

KEY MESSAGES

- Isolated severe thunderstorms are possible this afternoon and evening in the southern James River Valley in North Dakota.

- High chances of showers and thunderstorms exist beginning late tonight in southwest North Dakota, and spreading across most of western and south central North Dakota Tuesday and Tuesday night. Only a low risk of a strong or severe storm exists with this activity.

- A cooling trend is expected through midweek, before a warming trend occurs late this week and into next weekend.

UPDATE

Issued at 836 AM CDT Mon Jul 6 2026

Storms continue to diminish along the front this morning due to a low level inversion and decrease mixed layer instability. However, instability will increase as surface temperatures increase in the next few hours while thunderstorm activity may also have an uptick by the late morning and early afternoon hour. No updates are needed at this time.

UPDATE Issued at 643 AM CDT Mon Jul 6 2026

The low-level jet is gradually shifting eastward and weakening, and forecast soundings suggest the low-level inversion and an associated dry layer have become deep enough to result in the most probable parcel/updraft origination layer for the ongoing showers and thunderstorms to be near 700 mb. Parcels beginning from that level have relatively meager bouyancy, so the odds of a strong storm this morning have diminished. Otherwise, the cold front is still on track to cross the area today, and recent CAMs still support an isolated severe-storm risk this afternoon in the southern James River Valley.

DISCUSSION

Issued at 259 AM CDT Mon Jul 6 2026

A strong or isolated severe storm is possible early this morning as broken band of showers and storms moves across the area, then late this afternoon and evening there will be a risk of severe storms in the southern James River valley.

Early this morning, A broad, 40-45 kt low-level jet centered near 850 mb is present across western and central ND, and is contributing to isolated, high-based convection in central ND. A more prominent area of showers and thunderstorms is moving into western ND as of 07Z, and is associated with a more prominent shortwave trough aloft. This activity is expected to continue progressing eastward across western and central ND this morning, and will contain a risk of a strong or isolated storm, mainly through about 12z. This is supported by steep midlevel lapse rates and sufficient CAPE and shear for elevated storms. The overall risk is expected to be tempered by relatively dry and warm low-levels and related capping, though, and will become even more tempered after sunrise when the low-level jet wanes.

A surface cold front -- which is at least partially obscured in early-morning surface observations by convective outflow over eastern MT and northwestern ND - will progress east-southeast across the area today. Guidance expects the front to arc from near Rolla to Bismarck and Hettinger by late morning, and then along a line from near Grand Forks to Lamoure and Ashley by mid to late afternoon (i.e., 21z). Behind the front there's enough low-level cold air advection and increasing surface pressure gradient to foster breezy northerly winds. Ahead of the front, the air mass will undergo significant destabilization, with highs in the James Southern James River Valley in ND expected to be in the mid 90s F. Given surface dewpoints near 70 F, this is expected to contribute to strong bouyancy with MLCAPE on the order of 3000 J/kg in the pre-frontal environment. Forecast soundings do suggest some midlevel capping may linger along and ahead of the front in the southern James River Valley in ND, and the exact timing of the frontal passage will dictate whether or not convective initiation occurs there versus being relegated to the Red River Valley and adjoining northeastern SD. Deep- layer shear will be sufficient for organized clusters, and supercells given the magnitude of CAPE, with an attendant risk of large hail (up to around golf ball size) and damaging wind gusts up to 60 mph. Locally heavy rainfall is also possible given PWATs in the 1.75 inch range. The focus for this concern is mainly in LaMoure and Dickey Counties, though 00z CAMs are split on whether the storms will form in those counties, or just south and east of there.

Highs today will range from the mid to upper 70s in northwest ND to the 80s in southwest and central ND, and the mid 90s ahead of the front in LaMoure and Dickey Counties.

Broad surface high pressure will cover northern ND by tonight as the surface front settles across SD and extends back northwest into south central MT. That configuration will remain in place through Tuesday night. This should place southern ND in a cooler and more stable easterly low-level flow north of the front. As impulses embedded in west-southwest flow aloft cross the area, areas of showers and storms are expected, especially in southwest and south central ND. The first of these waves is expected to move out of MT and into southwest ND late tonight, spreading eastward during the day on Tuesday. Another impulse and its related precipitation may cross the area late Tuesday and Tuesday night. While there will be sufficient elevated CAPE for lightning -- and even the possibility of a strong or isolated severe storm, especially close to the ND/SD state line -- the overall severe-storm risk is expected to be limited on the cool side of the boundary in ND. PWATs will be around 1.5 inches though, favoring locally heavy rainfall. Ensemble and NBM-based probabilities of 0.50" or more of rainfall Tuesday and Tuesday night range from 50 percent in southwest ND to around 80 percent in the southern James River Valley in ND.

It will be much cooler on Tuesday with highs mainly in the 70s across most of the area, and with potential for it to be even cooler than forecast if clouds and precipitation are persistent enough in some areas during the daytime hours. Highs Wednesday are forecast to remain mainly in the 70s F as well, but a drier period is expected in between impulses aloft. Thereafter, a warming trend is still expected by late week as an upper-level ridge in the southwestern United States gradually amplifies to the north. The degree to which it amplifies will determine if there are any "ridge-running" thunderstorms in ND or not, and how warm it becomes. Some 00z guidance suggests the ridge could shift well into the Northern Plains in the Days 6-10 period. Ensembles suggest the highest, albeit still low to medium probability of a ridge-riding shortwave impulse with attendant thunderstorm potential could come Thursday afternoon and Thursday night before further amplification occurs. Highs will warm back into the 80s by late week, and ensembles suggest a high probability of 90s F returning by the weekend for much of the area.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 643 AM CDT Mon Jul 6 2026

VFR conditions are expected to prevail today and tonight. A cold front will move across western and central North Dakota today, passing through most terminals by 18Z, and KJMS by 19-21Z. The frontal passage will be followed by a shift to northerly winds that may gust up to 20-25 kt, especially in western and south central ND. A few showers and isolated thunderstorms are possible along and ahead of the front, with a chance of late afternoon and evening strong to severe storms south of KJMS before the front moves into SD. Late tonight, showers and storms may move into southwestern ND out of MT, potentially reaching KDIK after 09Z.

BIS WATCHES/WARNINGS/ADVISORIES

None.