textproduct: Bismarck

KEY MESSAGES

- Cooler and breezy today, with critical fire weather conditions in northwest and north central parts of the state and near- critical conditions elsewhere.

- Sub-freezing low temperatures are forecast across much of western and central North Dakota tonight.

- Warmer and windy weather next week could lead to daily critical fire weather conditions, especially Monday through Tuesday.

- Only occasional low chances for showers and thunderstorms through the end of next week.

UPDATE

Issued at 917 AM CDT Sat May 9 2026

Quiet weather remains over the area, with the forecast remaining on track.

UPDATE Issued at 643 AM CDT Sat May 9 2026

The forecast remains on track, although early morning temperatures across parts of northern North Dakota have now fallen well below freezing. Could see some patchy, shallow ground fog early this morning, with no impacts anticipated.

DISCUSSION

Issued at 525 AM CDT Sat May 9 2026

Northwest flow prevails over the Northern Plains early this morning, with water vapor imagery showing a shortwave moving across the Great Lakes. A cold front attendant to this wave has sagged into South Dakota and is ushering in another cool and dry air mass eminating from high pressure building over Alberta and Saskatchewan. Overnight/early morning temperatures have fallen into the lower and mid 30s across the northern half of the state where a Frost Advisory remains in effect until 9 AM CDT. Drier and cool weather is expected for the rest of today, with highs in the mid 50s to mid 60s. It will not be quite as windy as yesterday, but still expecting northwest winds around 15 to 20 mph with gusts to near 30 mph this afternoon. The breezy conditions combined with low RH has prompted the issuance of a Red Flag Warning for parts of northwest and north central North Dakota this afternoon and evening. For additional details and information, see the Fire Weather section below.

The Canadian high pressure will expand southeastward tonight. High confidence in a mostly clear sky and light winds has prompted us to blend our low temperature forecast for tonight closer to the 25th percentile of the NBM distribution. This gives sub-freezing temperatures to all but parts of the far southwest and far south central, and forecast lows as cold as the mid 20s across the northwest and north central. A Freeze Warning will likely be needed for most of western and central North Dakota tonight, but will hold off on issuance until the ongoing Frost Advisory runs its course. An upper level ridge will begin shifting off the Northern Rockies towards the Northern Plains on Sunday as the surface high slides through the Red and Upper Mississippi River Valleys. This turns off the wind machine for a day and provides a slight Mother's Day warm up to highs around 60 east to 70 west.

A prolonged period of daily critical fire weather conditions remains in the forecast for the upcoming work week. Specific details regarding this threat are discussed in the Fire Weather section below.

Southerly return flow will commence over the Northern Plains by Monday morning as the transient upper ridge slides across the Dakotas ahead of a potent shortwave ejecting off the southern Canadian Rockies. Latest forecast guidance shows south winds could approach advisory criteria Monday afternoon, mainly along and east of Highway 83. Lee cyclogenesis is forecast over southern Alberta late Sunday night, and the attendant warm sector/thermal ridge is forecast to reach western North Dakota by peak heating Monday afternoon. Median NBM percentile high temperatures continue to trend warmer, now firmly in the lower to mid 80s with very little spread in the full distribution across western North Dakota, and still mostly in the 70s east of Highway 83. The cold front attendant to the low is forecast to reach western North Dakota sometime Monday afternoon, but there is still some timing uncertainty to be worked out. Deterministic and ensemble guidance continues to show a narrow ribbon of CAPE ahead of the cold front, but there are questions whether it will be sufficient to support deep moist convection and also whether a mid level capping inversion will erode prior to the arrival of strongest forcing. A reasonable worst-case environment would feature around 500 J/kg CAPE with up to 60 kts of effective bulk shear, which would be sufficient to at least support a damaging wind threat. Nevertheless, any showers or sub-severe storms could mix strong wind gusts to the surface through evaporative cooling and downward momentum transfer mechanisms. The NBM probability of any showers and storms along and to the west of Highway 83 is very low, but the latest iteration of ensemble clusters paint a different picture.

Gusty northwest winds will trail the cold front, and could become quite strong on Tuesday. Ensemble cluster mean 850 mb winds in the post frontal air mass have trended upward closer to 35-40 kts, and there are now low probabilities for exceeding 50 kts in eastern North Dakota on Tuesday. The EFI is also beginning to show a stronger wind signal across the eastern half of the state on Tuesday. Given the time of year and trajectory of the shortwave/low, only a minor dent in high temperatures is projected for Tuesday, ranging from mid 60s northeast to mid 70s west. Beyond Tuesday, there is now higher ensemble confidence in an amplified upper ridge pivoting into the central CONUS, followed by timing uncertainty on a transition to a progressive high-amplitude wave pattern by the end of the week. This translates to above normal temperatures being favored and, hopefully, higher and more frequent chances for rain once the ridge breaks down. NBM temperature spread becomes larger for the second half of next week, but even the 25th percentile of high temperatures is near to above normal, and the 75th percentile begins to approach 90 degrees.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 643 AM CDT Sat May 9 2026

VFR conditions are expected through the forecast period. Could see some brief shallow ground fog early this morning that is unlikely to impact aviation. Light northerly winds this morning will become more northwesterly and increase to around 15 kts this afternoon, with gusts near 25 kts.

FIRE WEATHER

Issued at 525 AM CDT Sat May 9 2026

Although cooler temperatures in the 50s and 60s are expected this afternoon, dewpoints in the 20s and teens will yield minimum RH around 15 to 20 percent across much of northwest and central North Dakota. The wind forecast for this afternoon has backed off slightly, but still expecting to see northwest winds around 15 to 20 mph across most of the state. With forecast conditions barley touching on or just marginally exceeding critical values, we limited the scope of today's Red Flag Warning to 1) where confidence is highest in RH under 20 percent and 2) where there has been over 200 days since the last daily precipitation of over half an inch, which local research indicates could be a correlating factor to larger wildfires. The warning is in effect from 1 PM to 9 PM CDT for Divide, Williams, Burke, Mountrail, Renville, and Ward Counties. Should winds trend higher than what is forecast, a southeastward expansion of the warning through the Missouri River Valley would need to be considered.

Fire weather concerns are relatively lowest on Sunday, with forecast minimum RH around 20 to 30 percent and afternoon winds ranging from northerly around 10 mph in the James River Valley to variable around 5 mph or less across the rest of western and central North Dakota.

The most concerning period for fire weather this coming week is Monday through Tuesday. By midday Monday, southerly winds are forecast to increase to around 20 to 30 mph, strongest between the Missouri and James River Valleys where gusts could approach 45 mph. Even though southerly winds will be relatively lighter in western North Dakota to start the day, a cold front is scheduled to arrive from the west by mid afternoon. This cold front will shift winds to the northwest and could increase speeds as high as 30 mph, with gusts to 45 mph. This wind shift could occur close to the timing of lowest diurnal humidity, which could be under 20 percent in some areas. There is high confidence in minimum RH around 20 percent west to 30 percent central on Monday. But even with the slightly higher RH in central North Dakota, the southerly winds could still be strong enough to approach critical fire weather conditions.

The cold front will continue to progress eastward across the state Monday evening, shifting winds to the northwest. The strength of gusts trailing the front becomes less certain with the loss of diurnal heating, but deterministic guidance does show modest values of cold air advection and pressure rises paired with an increasing low level wrap-around jet. Ensembles continue to trend windier for Tuesday, with broad medium chances for northwest winds gusting in excess of 50 mph across the eastern half of the state. The sustained winds of 35 to 40 mph projected by the latest iteration of the NBM may be too high, but still resemble a reasonable worst-case scenario. The minimum humidity forecast for Tuesday is around 20 percent for the western half of the state, with even lower pockets in the far west. From the Turtle Mountains through the northern James River Valley, minimum RH is closer to 30 percent. Even though the strongest winds may not overlap with the lowest RH on Tuesday, there is still potential for critical fire weather conditions across all of western and central North Dakota. Areas of greatest concern on Tuesday include northwest parts of the state along and north of the Missouri River, all of central North Dakota, and especially areas from east of Lake Oahe to the southern James River Valley where a stronger wind outcome could place the entire afternoon and early evening in non-stop critical conditions.

On Wednesday, latest forecast guidance places the highest fire weather concerns back over western North Dakota, with southerly winds projected to increase to around 25 mph and minimum RH around 20 percent. Forecast details become less certain to end the week, but every day through at least Saturday has a potential for warm temperatures, low RH, and gusty winds.

BIS WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from 1 PM this afternoon to 9 PM CDT this evening for NDZ001>003-009>011.