textproduct: Bismarck

KEY MESSAGES

- Warmer today with highs in the mid 60s to mid 70s. A few isolated showers or thunderstorms could develop this afternoon and early evening.

- Well above normal temperatures through the first half of next week, with near-record highs around 90 to 95 Memorial Day and Tuesday.

UPDATE

Issued at 1000 AM CDT Sat May 23 2026

Visibility has begun to improve rapidly across western and central North Dakota at the time of this mid morning update. Pockets of sub 1 mile visibility linger across portions of the west, though even here erosion of the fog is evident on satellite. With fog expected to all but fully lift across most areas over the next hour, we have allowed the Dense Fog Advisory to expire on time at 10 AM CDT. Otherwise, low stratus is expected to lift off to the northeast through the remainder of the morning and afternoon, though the sky is will remain partly to mostly cloudy due to the development of a mid level deck later today. Overall, the forecast remains in good shape at this time.

UPDATE Issued at 638 AM CDT Sat May 23 2026

The only recent change to the Dense Fog Advisory was the addition of eastern Morton County. The fog is beginning to lift in southwest North Dakota, but areas from around Crosby to Glen Ullin remain socked in. Dense fog made a brief attempt at forming at the Bismarck Airport within the last hour, but it did not hold. Some low visibility is also being observed under thick low stratus to the east of the advisory, mainly of the 1 to 5 mile variety. There are a couple of webcams that show dense fog to the east of the advisory, but they are few and far between. Visibility should greatly improve between 8 and 10 AM CDT.

DISCUSSION

Issued at 408 AM CDT Sat May 23 2026

A double-barrel upper level low is spinning over the region this morning, with the two circulations over southeast Saskatchewan and where the Red River meets the international border. The attendant surface low continues work its way northeastward into the southern Red River Valley. As of 4 AM CDT, most of rain has departed our forecast area, with just a few isolated showers lingering in the James River Valley and a broader area of light stratiform rain from the Turtle Mountains down towards Rugby and Harvey. The associated stratus shield still extends as far west as the Highway 83 corridor. To the west of the stratus, areas of dense fog have settled in, especially from Tioga and Stanley down to Hettinger, but also now expanding to the northwest and east of that corridor. Divide, Mercer, Oliver, and Western McLean Counties were added to the Dense Fog Advisory, which remains in effect until 10 AM CDT.

The fog and clouds should lift or clear by the afternoon, giving way to more sun than clouds for the rest of the day. Flow aloft will remain cyclonic as the westernmost of the two upper lows digs back into north central North Dakota. Most CAMs have been advertising isolated showers or thunderstorms developing across parts of central North Dakota from mid afternoon through early evening. The highest probability for a shower or storm is in north central North Dakota, but it is still only around a 15 to 25 percent chance at any given location within that area. Other parts of the state cannot be ruled out of this potential, but the probability elsewhere is even lower than in the north central. The risk for strong to severe convection is very low to non-existent, with projected ensemble mean CAPE around 500 J/kg, effective bulk shear around 20 kts, and low equilibrium levels around 20 kft. Today will be much warmer than yesterday, but still near late-May normals with forecast highs in the mid 60s to mid 70s. Uneventful weather is anticipated tonight, with lows in the 40s.

The long-advertised stretch of well above normal temperatures begins on Sunday as upper level ridging starts to build over the Rockies and Plains. Confidence in the high temperature forecast through Wednesday is very high as the NBM 25th-75th percentile spread does not exceed 5 degrees over this time period. Widespread highs in the 80s are expected on Sunday. There is potential for a shortwave cutting through the building ridge Sunday afternoon and evening, which may allow a few isolated showers or thunderstorms to develop. In a relative sense, the highest probabilities for convection are once again in north central North Dakota. HREF members show uncertainty in the CAPE/shear parameter space, but the combined maximum of each would be sufficient for a stronger storm. Convection could be muted though by the overall mid-level rising height trend.

From Memorial Day through Wednesday, the upper ridge is forecast to become highly amplified and take on a negative tilt as a powerful trough digs into the western CONUS. The high temperature forecast over this time period has trended even warmer, with high confidence in near-record highs around 90 to 95 both Memorial Day and Tuesday, and still in the 80s on Wednesday. Strong south to southeast winds remain in the forecast for Tuesday and Wednesday, with sustained speeds around 20 to 30 mph and gusts mostly around 30 to 40 mph. Both the NBM and ECMWF EFI indicate the strongest winds are favored in western North Dakota each day. Shower and thunderstorm chances remain quite low through mid week, but do begin to increase in the west on Wednesday as shortwave energy ejects poleward from the western CONUS trough. In the case there are thunderstorms on Wednesday, projected moisture and instability/buoyancy would be sufficient for strong to severe convection, but shear looks much more questionable. Nevertheless, GEFS-based machine learning guidance continues to indicate a low severe potential in western North Dakota on Wednesday.

By the end of next week, there is increasing ensemble spread on the evolution of the western CONUS trough/upper low and the downstream blocking ridge. Regardless of the eventual outcome, all ensemble systems and clusters favor increasing chances for showers and thunderstorms with slightly cooler but still near to above normal temperatures heading into the first weekend of June.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 1000 AM CDT Sat May 23 2026

The 12Z TAF cycle begins with widespread low ceilings, primarily IFR to LIFR, across much central and eastern North Dakota, with areas of dense fog throughout western North Dakota. The dense fog has cleared from KDIK and is unlikely to return to KXWA. A gradual improvement in both visibility and ceilings is expected through the morning, with VFR conditions expected to prevail for the rest of the forecast period. A few isolated showers or thunderstorms could develop across central North Dakota this afternoon and early evening. Winds will become westerly to northwesterly around 10 kts later this morning through the afternoon, then turn southerly around 5-10 kts tonight.

BIS WATCHES/WARNINGS/ADVISORIES

None.