textproduct: Bismarck

KEY MESSAGES

- Widespread rain showers developing in western North Dakota late this afternoon, continuing and spreading east through Friday.

- Axis of higher rain amounts in western North Dakota, where up to 1 inch of rain could fall through Friday.

- Near to slightly below normal temperatures through Friday, warming to well above normal by the end of the holiday weekend.

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 /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1235 PM CDT Thu May 21 2026

VFR to MVFR CIGs this afternoon, becoming MVFR CIGs and or VIS in the showers and thunderstorms this evening and overnight. The shower and thunderstorm chances will increase later this afternoon in the west, and will stay west of the Missouri River today. Winds overall will be breezy with gusts to 25kts from the northwest in western ND, and from the southeast in central and eastern terminals. Thunderstorm chances should be done shortly after sunset, but the rain will continue and spread east through Friday.

BIS WATCHES/WARNINGS/ADVISORIES

None.