textproduct: Bismarck

KEY MESSAGES

- Temperatures remain well below normal through tonight when lows could fall to near or below freezing across much of western and central North Dakota.

- Warmer Wednesday through Friday, with medium chances for showers and occasional thunderstorms beginning Wednesday evening.

- Above normal temperatures favored this weekend and especially early next week.

UPDATE

Issued at 857 AM CDT Tue May 19 2026

Temperatures continue to warm across the state, while low stratus is beginning to scatter out. No major updates at this time as the forecast remains on track.

UPDATE Issued at 648 AM CDT Tue May 19 2026

A batch of light rain showers is moving through south central North Dakota early this morning, with some isolated light rain or sprinkle activity to the north and east. Occasional areas of light rain or sprinkles will remain possible across the eastern two thirds of the state through mid to late afternoon as an upper level trough pivots through, with chances diminishing from west to east.

DISCUSSION

Issued at 424 AM CDT Tue May 19 2026

An upper level trough extends from central Manitoba to the Great Basin early this morning, cutting through western North Dakota. At the surface, the Northern Plains lie between low pressure over Wisconsin and high pressure building over Wyoming. Extensive cloud cover across all but northwest North Dakota has kept overnight temperatures in the mid 30s to lower 40s thus far. Could still see a few degrees of cooling underneath the clouds, with more rapid cooling and perhaps some patchy fog where the cloud cover clears in the northwest early this morning. Despite much of the Freeze Warning and Frost Advisory trending towards not working out, do not plan on making any cancellations until temperatures begin rising for the day.

Strong cyclonic curvature vorticity embedded through the trough will pivot eastward through the state through this afternoon. This keeps low chances for light rain showers and sprinkles in the forecast. The cloud cover should continue to erode from west to east throughout the day, allowing high temperatures to return to around 50 east to near 60 west, still around 10 to 15 degrees below normal. As the upper trough departs to the east this evening, the Wyoming surface high will slide into eastern South Dakota with a ridge axis extending northward through eastern North Dakota. This should provide a favorable set up for strong radiational cooling over the eastern two thirds of the state. The current NBM forecast calls for widespread lows around 30 to 35 across central and eastern North Dakota, which will necessitate another around of frost/freeze headlines late tonight into Wednesday morning. Meanwhile, on the back side of the surface high, which is forecast to line up underneath a low- amplitude mid level ridge, increasing southeasterly surface flow paired with increasing mid to high clouds should keep overnight temperatures above freezing in much of the western third of the state, except perhaps in sheltered areas across the southwest.

An appreciable warm up to near or even above normal high temperatures in the 60s and 70s is forecast on Wednesday as a brief period of quasi-zonal flow is established over the Northern Plains ahead of a potent shortwave digging from Alberta southward into the Northern Rockies. The amplifying trough, which could feature a closed mid to upper low circulation along the Montana-Saskatchewan border, will turn flow aloft southwesterly for Thursday before the trough begins to shift eastward through the region on Friday. This could lead to a period of active weather beginning as early as late Wednesday afternoon in northwest North Dakota when high-resolution guidance is favoring the development of widely scattered showers and thunderstorms, spreading southward and eastward through Wednesday evening. An ensemble-averaged CAPE/shear parameter space (on the order of 500 J/kg and 25 kts) does not appear to favor stronger convection, but direct surface wind gust output from CAMs shows potential for some gusty winds with any storm that develops, which fits the modeled inverted-v thermodynamic profiles. The highest chances for showers are Thursday into Friday when the NBM paints widespread medium chances (around 40 to 60 percent) across the state, with its axis of highest chances shifting from western North Dakota on Thursday to eastern North Dakota on Friday. A few afternoon and evening thunderstorms could develop each of these 2 days as well, but there is uncertainty in the location of an inverted surface trough which is favored to contain a ribbon of up to around 500 J/kg CAPE. This is also tied to areal uncertainty of the highest QPF through Friday, with ensemble clusters showing a meridional axis of high probabilities for at least 0.25" QPF and medium probabilities for at least 0.5" as far west as against the Montana border and as far east as from the Devils Lake Basin to between the James and Red River Valleys. This leads to total ensemble QPF threshold probabilities per the NBM as broadly medium for exceeding 0.25" and low for exceeding 0.5" across most of western and central North Dakota. Temperatures are forecast to remain closer to normal Thursday and Friday, with highs around 65 to 70 and lows around 40 to 45. But any persistent areas of rain or clouds could cause locally cooler highs or warmer lows on either day.

The mid/upper trough is forecast to lift northeastward in time for the weekend. Ensemble guidance then favors a more progressive, high-amplitude wave pattern through early next week with large spread on the timing of troughs and ridges. Even so, there is a distinct warming trend to above normal temperatures, with highs favored to reach the 80s Sunday through Tuesday. Shower and thunderstorm chances remain very low (less than 20 percent) at this time from Saturday onward on account of the aforementioned uncertainty, but this may not be truly reflective of the more active pattern that is being projected.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 648 AM CDT Tue May 19 2026

Mix of ceilings ranging from IFR to VFR across western and central North Dakota to begin the 12Z TAF period. The general expectation is that ceilings will lift and/or clear from west to east throughout the day. A few light rain showers or sprinkles are possible this morning and afternoon, mainly across central and eastern North Dakota, with no impacts to aviation expected. Winds will remain northwesterly around 10-15 kts through this afternoon, strongest at KJMS. Then light and variable winds this evening will be followed by increasing south-southeast winds overnight.

BIS WATCHES/WARNINGS/ADVISORIES

None.