textproduct: Bismarck

KEY MESSAGES

- Hot and smoky conditions continue through at least the middle of the week, with highs around 90 to 100.

- Medium to high chances (40 to 70 percent) for showers and thunderstorms Wednesday afternoon through Thursday. A few storms could be severe.

UPDATE

Issued at 1155 AM CDT Tue Jul 28 2026

We added some slight chance pops over western ND this afternoon. Satellite imagery is picking up a decent shortwave near Glasgow MT and the atmosphere remains uncapped in the far west with some increasing mid-level lapse rates. Capping does increase through the afternoon so updrafts should find it harder to maintain themselves. One of the two earlier showers made it across the border and there is some additional shower activity pushing into the southwest-west central. Thought a slight chance would be justified. In the east, the instability and shear is more impressive, but so is the capping. Perhaps around the Turtle Mountains into the JRV, a few thunderstorms may be possible this afternoon. If so a stronger storm can not be ruled out. The instability increases here this afternoon but the shear tapers off.

UPDATE Issued at 1000 AM CDT Tue Jul 28 2026

The dense fog advisory has been allowed to expire. Visibilities continue to improve, but there will be some patchy lower visibilities for the next hour or so. We also adjusted sky cover down a bit in the south through the morning. Motoring a few showers approaching the border from eastern Montana. There are a couple of shower that may enter southwest McKenzie in the next hour but not sure they will survive. Additional showers a little farther west will take a bit longer to reach ND and we do have some low pops in the far west this afternoon.

UPDATE Issued at 650 AM CDT Tue Jul 28 2026

Isolated showers continue roam through the James River Valley early this morning. Do not anticipate this activity to persist into the afternoon, and the probability of a thunderstorm is very low. Dense fog also continues across north central North Dakota early this morning. Observations show little remaining dense fog in Burke County, but Estevan recently reported 1/8 mile visibility. The fog has also spread south into northern Kidder and Stutsman Counties, but there is lower coverage of dense fog there. No changes were made to the advisory for this update.

DISCUSSION

Issued at 515 AM CDT Tue Jul 28 2026

Upper level ridge axis lies across eastern Montana/Wyoming early this morning. A benign surface pattern is analyzed over the Northern Plains, with mesoscale high pressure from southern Manitoba into northeast North Dakota. Dense fog has developed along and northeast of Highway 52, as far south as the Highway 200 corridor. A Dense Fog Advisory remains in effect for these areas until 10 AM CDT. Meanwhile, weak warm air/moisture advection underneath the right entrance region of an upper level jet has initiated isolated showers with an occasional thunderstorm from the northern James River Valley to between Lake Oahe and the southern James River Valley. This convection may continue meandering through this part of the state into the mid/late morning hours before dissipating, but forecast confidence is low as this convection was not modeled very well.

The upper level ridge will remain in place today. High temperatures should return to the 90s to near 100 with lesser cloud cover than yesterday. Smoke aloft remains a wild card though, and could keep temperatures a few degrees cooler. A mention of patchy smoke was maintained in the forecast through tonight in continuity with HRRR/RAP near-surface smoke guidance, although the correlation between modeled smoke concentrations and observed visibility is subjectively verifying with mixed results at best. Nevertheless, confidence remains high in at least some amount of smoke in the air through the middle of the week, whether it be aloft or at the surface. The upper ridge continues to build and pivots eastward on Wednesday ahead of shortwave energy ejecting off the Northern Rockies, bringing the thermal ridge back into the western Dakotas. The NBM shows high confidence in high temperatures around 100 across much of western and central North Dakota, with maximum heat indices also around 100 along and to the west and south of the Missouri River Valley.

With weak disturbances continuing to round the top of the ridge and forecast highs near convective temperatures, occasional isolated showers and thunderstorms cannot be ruled out this afternoon and evening. We are broadly not carrying mentionable PoPs, as the point-specific probability for a shower or storm at any given location is less than 15 percent. But in general, CAMs would indicate relatively higher odds of convection initiating across southern and eastern North Dakota than to the north and west. CAPE is forecast to decrease across western North Dakota this afternoon, but the eastern half of the state could see 1000-2000 J/kg CAPE with around 25-30 kts of deep layer shear during the late afternoon and early evening. Therefore, a stronger storm cannot be ruled out in the James River Valley over the aforementioned timeframe, which a couple CAMs have been consistently simulating.

Through Wednesday morning, a turning of the low level wind field to southwesterly will bring warm air/moisture advection into western and central North Dakota. CAMs indicate a low probability of shower and thunderstorm development in response to this forcing, with any storms likely remaining elevated and sub-severe. There is a very low probability scenario though where this activity becomes rooted in the boundary layer before departing into eastern North Dakota early Wednesday afternoon. The greater focus for strong to severe convection will be along a lee trough near the MT/ND border mid Wednesday afternoon. Model guidance is consistent in initiating deep moist convection by late afternoon, albeit with timing and coverage discrepancies. Storm mode could be mixed initially, with shear vectors more perpendicular to the lee trough in southern North Dakota, but more parallel to it farther north. Upscale growth into clusters is favored as storms propagate eastward into central North Dakota late Wednesday evening into the overnight hours, with more favorable maintenance of convection across the north where buoyancy, shear, and forcing could all be stronger. The tornado risk appears very low, but a favorable setup could briefly emerge in far northwest North Dakota early Wednesday evening. However, current HRRR/RAP hodographs at Crosby show crosswise vorticity in the 0-1 km layer, rendering tornadogenesis less favorable.

Medium chances for showers and thunderstorms continue on Thursday as broad mid level shortwave troughing in the middle of the longwave ridge stalls over the Northern Plains. A medium to high CAPE and low to moderate shear environment could support a few severe storms Thursday afternoon and evening, but details remain uncertain. A slight cool down is expected on Thursday, but with highs remaining in the mid 80s to mid 90s. Similar high temperatures carry into Friday as the shortwave dives southeast into the Upper Mississippi and Lower Missouri River Valleys. This forces the upper ridge back over the western CONUS where it looks to rebound, but that could be temporarily inhibited by another shortwave ejecting off the Northern Rockies on Friday which could bring a few thunderstorms into western North Dakota later in the day. The upstream ridge is favored to become highly-amplified once again over the weekend and develop a positive tilt as a strong upper low digs into British Columbia. The thermal ridge axis reaches the western Dakotas on Sunday, which could allow high temperatures to return to 100 to 105. A strong southerly return flow is also forecast on Sunday, which could increase fire weather concerns. A cold front is forecast to move through the state late Sunday into Monday, which may be accompanied by gusty winds and scattered showers and thunderstorms. The post-frontal air mass should bring much cooler temperatures to start the work week, with highs mostly in the 70s and 80s. But there are signs in longer-range ensembles that the upper ridge could try to build into the central CONUS once again later next week.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 1155 AM CDT Tue Jul 28 2026

VFR conditions are expected through the 12Z TAF period. Generally light and variable winds through the period 12 knots or less. Isolated thunderstorms can not be ruled out, but too much uncertainty to even include a PROB30 at any TAF site. Patchy fog can not be ruled out either late tonight into Wednesday morning but too much uncertainty to include any fog at this time.

BIS WATCHES/WARNINGS/ADVISORIES

None.