textproduct: Bismarck

KEY MESSAGES

- Widespread showers with scattered thunderstorms continue today into tonight.

- Marginal (level 1 out of 5) severe weather threat this afternoon and evening over much of southwest and south central North Dakota.

- Medium to high precipitation chances continue in the forecast from Monday night through Wednesday. Low to medium chances through the remainder of the week.

UPDATE

Issued at 641 AM CDT Sun May 31 2026

Going forecast remains on track with only minimal changes needed at this time.

DISCUSSION

Issued at 321 AM CDT Sun May 31 2026

Current surface analysis places low stretching from eastern Montana into western South Dakota, with high over the Great Lakes. Upper level analysis places trough stretching through Montana into Wyoming, with ridge through the Midwest. Over our area, areas of showers continue to lift northward ahead of the aforementioned upper through, with thunderstorms now mainly confined to the southern James River Valley where the higher instability (~500 J/Kg) is now noted.

For today, aforementioned upper trough closes off over Montana with a variety of short waves continuing to wrap around bringing continued rain showers to the area. Instability will be on the increase this afternoon, thus an increasing chance for thunderstorms. Greatest instability (~1000-1500 J/Kg) looks to reside mainly over southwest into south central North Dakota later this afternoon into this evening. Although deep layer shear appears to still be a bit on the low side (though higher than yesterday), still think the potential for a few marginally severe storms exists with hail up to one inch in diameter and wind gusts to 60 mph. A frontal boundary pulling into the area Sunday night into early Monday will sustain additional precipitation chances.

Monday may see a brief break in precipitation over most locations except possibly north central North Dakota where aforementioned front stalls out. As we go through Monday, aforementioned Montana low wraps itself northward and even retrogrades a bit over southern Saskatchewan towards the Alberta border. The next in a series of waves push into the area late Monday, with increasing precipitation chances gradually sliding through our area through late Tuesday, even lingering into Wednesday. NBM probabilities of seeing over an inch of additional precipitation with this system have gone up a bit, now at about 20 to 40 percent for a notable portion of western North Dakota. In addition, there will be a severe threat on Tuesday as instability will be on the increase later in the day with 0-6km shear around 35 to 45 kts. Thereafter the flow pattern remains generally westerly and active, bringing continued low to medium precipitation chances to close out the work week.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 641 AM CDT Sun May 31 2026

Periods of rain showers will continue moving through the area through this evening before gradually dissipating from southwest to northeast late tonight. Mainly MVFR ceilings are forecast, though there will be a period of IFR ceilings over various locations this morning, and again over the James River Valley late tonight. Periods of thunderstorms will also be in the mix through the forecast period, mainly addressed with separate PROB30 groups.

BIS WATCHES/WARNINGS/ADVISORIES

None.