textproduct: Bismarck

KEY MESSAGES

- Areas of fog, dense at times across much of western and central North Dakota this morning.

- Seasonable temperatures through early next week, with highs mostly in the 60s and 70s.

- Medium to high chances for rain across western and far southern North Dakota tonight through Friday, continuing in the west through much of the weekend.

UPDATE

Issued at 422 AM CDT Thu Sep 17 2026

We issued a Dense Fog Advisory for most of western and central North Dakota. Fog continues to expand across the forecast area with many locations at or below a quarter mile. Included all but a portion of the west central. There are some areas within the advisory where visibilities are okay, but needed to connect areas and we do expect conditions to deteriorate as we head towards sunrise.

DISCUSSION

Issued at 343 AM CDT Thu Sep 17 2026

Currently, surface high pressure is situated over southern Saskatchewan and Manitiba, and into northeast North Dakota. Clear to partly cloudy skies were noted across western and central ND, but patchy fog was indicated on Satellite and looks to be increasing in areal coverage. The extent of fog and possible hazards will be the main forecast issue in the short term period.

After today, the focus shifts to an impulse that tracks across South Dakota tonight into Friday morning, bringing precipitation to far southern ND, then to western ND this weekend as an upper level low approaches the area.

The impulse tonight should bring some beneficial light rains to far southern portions of the forecast area. Yesterday at this time there was a northward trend in the qpf. If anything, today the trend is back south, with only the far southern tier counties seeing more than a tenth of an inch. The probability for at least a quarter inch of rain from 1 AM Friday to 1 AM Saturday, is around 50 percent over the far southern James River Valley, and quickly tapers as you go north.

There is another area of showers, and possibly a thunderstorm that models continue to focus on, the northwest portion of the state, and possibly into the far north central. An area of elevated instability is situated from northeast MT/northwest ND and into southern Manitoba, ahead of an approaching northern stream wave and associated cold front. This is also within an area of strong warm advection and increasing moisture transport ahead of the Canadian cold front. Unless you get a thunderstorm, don't think the qpf amounts will amount to much up here, with the higher totals remaining in southern Canada. The latest NBM is showing low to medium probabilities (20 to 60%) for at least a quarter inch over northwest ND in the 24 hour period ending 7 PM Friday. That instability axis lingers through Saturday along the International Border, but qpf amounts here remain light with high pressure situated over southern Manitoba.

The upper level low will be tracking through the Northern Rockies and into the Northern High Plains Saturday through Saturday night, then into the Northern Plains Sunday through Sunday night. Overall, the trend has been drier with this system. The track of the upper level low looks to be farther south. We see sort of a High over Low blocking pattern develop with an upper level ridge and surface high pressure situated over southern Canada, keeping the track of the low to our south and limiting the northward extent of moisture. QPF totals continue to diminish over western ND. QPF totals in western ND from Friday evening through Sunday evening range from a quarter to a half inch, and are mostly limited to the far northwest and far southwest, with less than a couple tenths most areas. On Monday, the upper low exits the area and any low precipitation chances will be limited to southern portions of the forecast area. Beyond Monday, there may be another wave bringing some low precipitation chances mid-week, but uncertainty in this remains high.

Temperature wise we remain seasonable with high temperatures remaining mainly in the 60s and 70s and low temperatures in the 40s to lower 50s. There is a signal for a gradual warming trend as we head through the work week, with deterministic and ensemble models showing an upper level ridge over the central portion of the U.S. by the end of the work week. However there is uncertainty as to whether or not this is a strong ridge yielding warmer temperatures, or a flatter ridge in our neck of the woods, keeping temperatures closer to normal. Although NBM ensemble temperatures do increase gradually through the week, NBM ensemble temperature spreads also increase through the week. Confidence in a gradual warming trend in medium to high, but confidence in a significant warm-up, although possible, remains low at this time.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1223 AM CDT Thu Sep 17 2026

Low ceilings and fog are forecast to develop across much of western and central North Dakota late tonight into Thursday morning. Conditions should improve back to VFR by Thursday afternoon. Expect light and variable winds through tonight, becoming east to southeast during the day Thursday at around 10 kts in central North Dakota to near 20 kts in the west.

BIS WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 11 AM CDT /10 AM MDT/ this morning for NDZ001>005-009-010-012-013-018>020-022-023-025-033-035>037- 040>044-046>048-050-051-055>062.