textproduct: Bismarck

KEY MESSAGES

- Showers and thunderstorms mainly in western and north central North Dakota this evening. Thunderstorm activity diminishes overnight, while showers continue before spreading eastward Friday.

- Below average temperatures Friday, then warming to well above average by the end of the holiday weekend.

UPDATE

Issued at 939 PM CDT Thu May 21 2026

A relatively narrow line of showers and thunderstorms continues mainly from Hettinger to Richardton to just west of Minot. As has been expected, thunderstorm activity has really decreased over the past hour or so as the sun set. This trend is expected to continue, though suspect isolated thunderstorms will remain possible until midnight and possibly through the night. With weak mid-level winds, storm motion has been erratic to say the least with individual cell movements often seeming to contradict one another. Overall though, the axis of heaviest rain has remained relatively stable as one would expect with the stationary front.

UPDATE Issued at 717 PM CDT Thu May 21 2026

Showers and thunderstorms have developed along a stationary frontal boundary over parts of southwestern North Dakota, and to a lesser extent, parts of the north central. A strong storm had initially developed southwest of Dickinson, though has since decreased in intensity. Model guidance suggests instability should rapidly decrease as the sun sets resulting mostly in showers during the overnight hours. Though a few rumbles of thunder cannot be completely ruled out. Shower activity overnight will remain mostly concentrated along the frontal boundary before expanding eastward Friday.

DISCUSSION

Issued at 230 PM CDT Thu May 21 2026

Currently a medium size trough and upper low is sitting over Montana and Wyoming. Upstream in the Pacific Northwest a ridge or zonal flow is forming. At the surface the collocated surface low is in southern Canada, with a stationary front sitting in an inverted trough placed over western North Dakota. Along the positive vorticity side of the upper level trough in eastern Montana, showers have been on going. This afternoon as surface temperatures increase, around 1500 J/kg of CAPE will be present along the front. With shear around 30kts, thunderstorms will form and train south to north along the front since the shear vector will be parallel to the front. With very skinny CAPE profiles and high relative humidities through the upper levels, there is only a small chance of severe hazards. So the highest risk from the storms will be heavy downpours. The CAMs agree on the location being somewhere between Beach, and Glen Ullin. Timing looks to be between 5 and 7pm CT. With the front remaining stationary along with the inverted trough, the storms should stay west of the Missouri River through the evening.

Tonight a surface low moving out of Wyoming from the bottom of the upper level trough will start to move northeast. By Friday morning it will form into it's own stacked low and be in northern South Dakota. Therefor Friday will be slightly cooler with widespread rain across most of the state. This rain will last through most of the day, ending west to east as the low continues into northern Minnesota Friday night. An axis of higher QPF is will occur with the thunderstorms this evening, and the front enhancing lift through Friday in western ND. There is a medium to high chance of 1 inch of QPF on a north south line centered on Dickinson between South Dakota and New Town. Another higher area of QPF is forecast in southeast ND when the low wraps up and moves through. The majority of that QPF will fall Friday afternoon.

Through this weekend zonal flow will setup across the Northern Plains leading to very warm temperatures, both aloft and at the surface. By Monday expect highs near 90 in the west and central. These above normal temperatures will continue through the week. In the latter part of next week a large upper level low could move through, although there is an incredible amount of uncertainty in location and timing if it does occur. NBM does have low PoPs for this, and temperatures look to stay in the upper 70s or lower 80s.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 717 PM CDT Thu May 21 2026

Showers and thunderstorms have developed along a stationary front over parts of southwestern and north central North Dakota. So far, most thunderstorm activity has been confined to the southwest. Thunderstorm activity will diminish as the sun sets, though showers should persist through the night. Still, an occasional rogue rumble of thunder will remain possible. Showers, perhaps with a few rumbles of thunder, will then expand eastward across the state on Friday. MVFR ceilings are expected to enter southwestern North Dakota later tonight before MVFR/IFR ceilings impact most of the state Friday. Ceilings will also gradually improve from west to east.

BIS WATCHES/WARNINGS/ADVISORIES

None.