textproduct: Bismarck

KEY MESSAGES

- Very hot this weekend, with high temperatures around 100 in southwest North Dakota today and south central North Dakota on Sunday.

- Windy Sunday and Monday, with near-critical fire weather conditions expected across much of the western half of the state.

- The first half of the upcoming work week should be much cooler, with highs in the 70s and 80s.

- Low to medium chances for showers and thunderstorms late Sunday night through Monday afternoon. A few storms could be severe in central and eastern parts of the state.

UPDATE

Issued at 955 AM CDT Sat Aug 1 2026

Little needing updating this morning. RGB Geocolor satellite imagery showing some smoke aloft, although surface observations have not reported in restrictions yet. Otherwise expect hotter temperatures today along with mainly dry conditions. Overall the forecast remains on track.

UPDATE Issued at 646 AM CDT Sat Aug 1 2026

Patchy shallow fog has developed in the James River Valley. The fog should not last beyond 8-9 AM CDT and should remain limited to low-lying areas. Farther north, scattered light showers continue to stream over the Turtle Mountains early this morning. This activity should dissipate or shift off to the east by around 8 AM CDT. Other than these two features, an uneventful and sunny but hot day is expected, with increasing southerly winds in central North Dakota.

DISCUSSION

Issued at 430 AM CDT Sat Aug 1 2026

Anticyclonic northwest flow lies over the Northern Plains early this morning, with a traditional ridge axis from the Great Salt Lake to along the Alberta/Saskatchewan border and an east- northeast pointing axis from southern North Dakota to Lake Superior. There is a 700 mb shortwave traversing southern Saskatchewan underneath the broad upper ridge, with low level jet induced warm air advection in southeast Saskatchewan and southwest Manitoba. This has initiated a small cluster of showers and thunderstorms that has crossed into far north central North Dakota as of 4 AM CDT. Confidence on maintenance of this convection remains low, as forcing is forecast to weaken and downstream MUCAPE is analyzed to be only 100-200 J/kg. After this activity dissipates or departs to the east, quiet weather is expected to prevail through the rest of the day, with increasing southerly return flow over central North Dakota between a downstream surface ridge and upstream lee troughing. Temperatures are projected to reach around 100 degrees in southwest parts of the state this afternoon, with 90s northwest and central and mid to upper 80s from the Turtle Mountains through the James River Valley. Dewpoints in the mid 40 to mid 50s should keep heat indices below 100 in southwest North Dakota this afternoon, and the probability of widespread temperatures at or above 100 is not high enough to issue a Heat Advisory. But it will still be a very hot day, and precautions should still be taken to avoid over-exposure to the heat. Very few, if any clouds are expected today, but smoke aloft could produce a hazy sky.

From this evening into Sunday morning, the main upper ridge axis will be tilted in a positive direction as a well-advertised upper low crosses the Canadian Rockies. An overnight southerly breeze around 10 to 15 mph should keep low temperatures in the 60s to lower 70s. Southerly winds will then strengthen over central North Dakota by Sunday afternoon, and may approach advisory criteria of sustained winds near 30 mph and gusts near 45 mph. This will take place ahead of a cold front being driven in by the Canadian low. By mid afternoon, the cold front is projected to be roughly located from the Turtle Mountains to Standing Rock Reservation. High temperatures along the frontal interface in the southern half of the state could easily reach 100 degrees, and few locations could approach 105 on account of compressional heating. Moisture return in the downstream southerly flow could bring mid 50s to mid 60s dewpoints back into central North Dakota, which introduces a higher probability of heat indices reaching 100 Sunday afternoon. The latest NBM guidance highlights this in a corridor from Bismarck through eastern Grant and western Sioux Counties, and the maximum wet- bulb globe temperature risk also reaches the Extreme category in this area. Elsewhere on Sunday, expecting highs in the 90s surrounding the aforementioned corridor, with mid to upper 80s in both the far northwest and southern James River Valley. Winds behind the cold front are not projected to be overly strong, but could still gust to near 30 mph in far western North Dakota Sunday afternoon. With humidity falling into the 15 to 25 percent range across the western half of the state, and perhaps closer to 10 percent in the far southwest, at least near- critical fire weather conditions are expected. There are currently two separate areas with the highest probabilities for meeting Red Flag Warning criteria on Sunday: one across Golden Valley, Slope, and Bowman Counties and another in eastern Sioux, western Emmons, and southern Burleigh Counties. But these probabilities are still not quite high enough for a Fire Weather Watch, and the disjointed areas of highest probabilities lowers confidence in spatial coverage. Further complicating matters is that each of the 2 areas of concern occur at different times of day (early afternoon far southwest and mid to late afternoon south central). A final note about Sunday is that HRRR/RAP guidance projects a significant increase in near-surface smoke concentrations with the arrival of the cold front, which is a regime the modeling has proven to perform well in.

The cold front is forecast to stall from northeast to south central North Dakota Sunday evening as its parent cyclone begins to occlude over central Saskatchewan. It is very doubtful that the cold front will be able to initiate any convection on its own prior to sunset Sunday evening, with strong capping in place and stronger mid/upper level ascent lagging behind. Heading into Sunday night though, shortwave energy embedded in southwest flow aloft could begin traversing the region as the rate of mid level height falls increases, and northeastward moisture transport from the nocturnal low level jet is also forecast to strengthen. This increases probabilities for elevated convection developing over southern and eastern North Dakota late Sunday night into early Monday morning. The challenge with elevated convection is determining the CAPE/shear parameter space of its elevated inflow layer, which itself carries low predictability. NAM soundings would suggest an inflow layer with little to no inhibition of at least 3 km AGL, and the associated hodographs do show some length and curvature from 3-11 km (GFS soundings were briefly examined, but think its low-level moisture dry bias is interfering). The couple of CAMs that reach this forecast time range do show showers and storms developing Sunday night, but with varying coverage and intensity.

On Monday, the stalled frontal boundary is progged to slowly shift eastward as a separate shortwave ejects off the Northern Rockies. This shortwave will bring a secondary push of cooler air into the region, with daytime north to northwest winds around 25 mph. The high temperature forecast continues to trend cooler, now at only around 70 in the far northwest to around 80 to 85 south. But the dewpoint forecast is also trending lower, keeping minimum RH as low as 20-25 percent in the southwest. Even though fire weather concerns will not be as widespread on Monday compared to Sunday, there is actually a higher probability of meeting Red Flag criteria in Slope and Bowman Counties. The other concern for Monday is whether severe storms will develop within our forecast area or remain off to the east (or perhaps not develop at all). It seems that the most likely outcome is for severe convection to stay just to our east, and morning convection could exert influence on the afternoon environment. But the NBM does show low to medium probabilities for CAPE exceeding 1000 J/kg in the southern James River Valley, which would easily be sufficient for severe storms given around 50 kts of deep layer shear. And the mentioned probabilities would actually be higher and extend farther back to the north and west if GEFS members were excluded on account of their low CAPE biases.

Confidence remains high that Tuesday will be the coolest day of the week with below normal high temperatures in the 70s as surface high pressure slides in under longwave troughing. A quick return to near or above normal temperatures is then favored by the NBM through the end of the week. Ensemble clusters remain undecided whether the Northern Plains will be closer to the radius of influence of a Hudson Bay low or Rockies ridge. Despite this, mean 850 mb temperatures of each cluster show little difference through Friday. Aside from the Sunday night/Monday time period, chances for rain remain very low. This could change if the Hudson Bay low ends up deeper and augmented farther west, but even then there are no signs of any significant rain-makers on the horizon.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 646 AM CDT Sat Aug 1 2026

Patchy fog has developed at KJMS, and was reducing visibility to 1/4SM to start the forecast period. The fog should clear by 13-14Z. VFR conditions are otherwise expected through the forecast period. Smoke from distant wildfires may persist aloft, but it is unlikely to restrict surface visibility until Sunday afternoon. Winds will become southerly and increase to around 15 kts across southwest and central North Dakota later today, with lighter southwesterly winds in the northwest and southeasterly winds at KJMS. Then this evening through tonight, all terminals can expect south-southeast winds around 15 kts, with some higher gusts possible.

BIS WATCHES/WARNINGS/ADVISORIES

None.