textproduct: Bismarck

KEY MESSAGES

- Low to medium chances for showers and isolated thunderstorms across western and north central North Dakota late this afternoon through the evening, then medium to high chances across the western half of the state Thursday through Friday.

- Temperatures remain closer to normal through Friday, then warm to well above normal by the end of the holiday weekend.

UPDATE

Issued at 1228 PM CDT Wed May 20 2026

An upper level wave continues to move across the north central no rain has been reported so far. Chances for showers will increase this afternoon. No major updates are needed at this time as the forecast remains on track.

UPDATE Issued at 1034 AM CDT Wed May 20 2026

An upper level wave moves across the northwest this morning mainly with sprinkles expected. No major updates needed at this time, the forecast remains on track.

UPDATE Issued at 649 AM CDT Wed May 20 2026

The forecast remains in good shape. Temperatures in the Frost Advisory have mostly risen into the upper 30s to mid 40s, but there are still a handful of locations in the mid 30s scattered throughout the advisory, so will just let it continue for now.

DISCUSSION

Issued at 438 AM CDT Wed May 20 2026

Early morning surface analysis shows high pressure from the Red River through Lower Missouri River Valleys, with a low pressure trough along the Alberta-Saskatchewan border into northeast Montana. Flow aloft is turning more zonal as a transient mid level ridge precedes a shortwave digging down the Canadian Rockies. The placement of the surface high has allowed temperatures to fall to near or below freezing across the eastern half of the state. Meanwhile, an increase in southerly return flow is keeping temperatures above freezing in the western half of the state, except in a few low- lying, sheltered spots. The Freeze Warning and Frost Advisory remain in good shape. A weak shortwave that appears to be embedded in the mid level ridge is producing light showers aloft, little of which is reaching the ground on account of a very dry low level layer of air. A slight chance of sprinkles remains in the forecast as this feature crosses northern North Dakota this morning.

A southeastward advancement of the upstream surface trough will squeeze the pressure gradient over central North Dakota later this morning and afternoon, increasing winds to near 30 mph and gusting to 40 mph. But temperatures are forecast to be much warmer today, with highs ranging from the mid 60s east to mid 70s west. This could lead to near-critical fire weather conditions in parts of western and central North Dakota this afternoon, but the lowest RH of around 20 percent in the southwest is not forecast to overlap with the strongest winds between Highways 83 and 281.

By late afternoon today, mid level DCVA is forecast to spread into western North Dakota ahead of a closed low circulation spinning over southwest Saskatchewan. At the surface, a low pressure with an attendant warm front to the east, dryline to the south, and cold front to the southwest is forecast to enter northwest North Dakota at a similar time. CAMs are in agreement on widespread shower and thunderstorm activity initiating closer to the cold front in eastern Montana this afternoon, but also indicate a lower degree of coverage developing into western and north central North Dakota by early evening. There is potential for up to 500 J/kg of CAPE to build just ahead of the dryline, but models are fairly consistent in keeping the buoyancy displaced downstream of stronger shear, and HRRR/RAP soundings show a skinny CAPE profile with equilibrium levels only approaching 25,000 ft. Stronger convection is therefore highly unlikely late this afternoon and evening, but the inverted-v thermodynamic profiles could support gusty winds. Showers and storms are forecast to gradually dissipate late this evening into tonight, which will have milder low temperatures in the upper 30s to mid 40s.

On Thursday, the mid/upper level trough axis is forecast to reorient itself and deepen from southern Saskatchewan to northern Utah, inducing lee cyclogenesis with an inverted surface trough extending northward through the western Dakotas. The inverted surface trough will be the focal axis for high chances of showers Thursday afternoon through Thursday night. There is still some uncertainty on the placement of the inverted trough and associated maximum QPF, but the range has narrowed in scope to as far west as the Montana border and as far east as a line roughly from the Turtle Mountains to the Standing Rock Reservation. The NBM places its averaged maximum QPF axis from around Hettinger to Stanley, with high chances of exceeding 0.25" and low to medium chances of exceeding 0.5". But embedded thunderstorms along a ribbon of up to 1000 J/kg CAPE could produce locally higher amounts, as indicated by the HREF localized probability-matched mean QPF showing pockets of 1-2". Training convection, high deep-layer RH, and precipitable water approaching 75th-90th climatological percentile values near 1 inch could also contribute to enhanced rainfall rates on a localized basis.

The mid/upper trough is forecast to pivot into the High Plains on Friday with two distinct vort maxima over southeast Saskatchewan and northeast Colorado, respectively. Numerous showers are likely to persist along the inverted surface trough on Friday, which may only shift slightly to the east. But there is a much lower risk for thunderstorms on Friday as guidance is showing little to no CAPE. There are several potential outcomes for multi-day rain totals depending on how much or little the inverted surface trough shifts around. If it remains nearly stationary all the way through Friday, there could be a narrow corridor of +1 inch amounts surrounded by widespread amounts under a quarter of an inch. If the inverted trough does shift eastward, there could be a broader area or perhaps two separate areas of around half an inch. The latest NBM shows a narrow axis of medium chances (50 to 60 percent) for exceeding half an inch of rain Thursday through Friday night from Hettinger to just west of Minot, with low chances (10 to 20 percent) for exceeding 1 inch.

Temperatures will remain closer to normal Thursday and Friday, although showers and associated cloud cover could cause some deviations. Friday in particular looks like a day where a large portion of the area could see cooler daytime temperatures under persistent clouds and shower activity. Overnight temperatures are forecast to remain well above freezing, with only parts of southwest North Dakota having a low chance of falling into the mid 30s Friday night. A significant warm up continues to be strongly favored by ensemble guidance through the holiday weekend as there is now increasing ensemble agreement on mean ridging over the central CONUS. The NBM shows moderate to low spread given the forecast time range with highs in the mid 70s to mid 80s on Sunday and around 80 to 90 degrees on Memorial Day. Chances for rain under this pattern are low, but there could be some shortwaves traversing the top of the ridge over the Northern Plains before the ridge becomes more amplified. Above normal temperatures of highs in the mid 70s to upper 80s are favored to continue through the middle of next week, with increasing uncertainty in the eastward progression of the central CONUS ridge as a stronger wave digs down from the Gulf of Alaska.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1228 PM CDT Wed May 20 2026

Winds will remain out of the south this afternoon with showers and maybe a thunderstorm or two possible across the west. VFR conditions will persist through the period with winds picking up tomorrow out of the southeast.

BIS WATCHES/WARNINGS/ADVISORIES

None.