textproduct: Bismarck

KEY MESSAGES

- Showers and thunderstorms late Sunday evening through Monday night. There are medium to high chances to exceed 1 inch of rain from south central to northeast North Dakota. A few storms could be strong.

- Temperatures favored to remain near to slightly above normal until late next week.

UPDATE

Issued at 156 AM CDT Sun Sep 27 2026

Patchy dense fog persists ahead of the stalled frontal boundary from around Lake Oahe to the James River Valley. Model guidance has been persistent that the front should slowly surge southeastward through the night, clearing out the fog. But that has yet to be observed, and the footprint of the fog has shown little to no change in the last couple hours. The fog is likely to persist where it is currently observed until winds turn to the west/northwest.

Radar is picking up some returns entering the southwest corner of the state. These appear to be high based showers with little to no precipitation reaching the ground.

UPDATE Issued at 937 PM CDT Sat Sep 26 2026

Overall, the cold frontal boundary has stalled in south central North Dakota, though continues to gradually move eastward in the north central. Dewpoints in the upper 50s and low 60s persist east of the front, but dip into the 30s in western ND. Overall, this should keep conditions generally fog free in the west and north central. However, fog development has recently been observed ahead of the frontal boundary, including in south central parts of the state. As the entire front starts moving east again tonight, fog should dissipate from west to east as much drier air continues filtering in.

UPDATE Issued at 654 PM CDT Sat Sep 26 2026

Models are suggesting fog development again tonight in the south central and James River Valley. This is contrary to rapidly drying dewpoints and model forecast soundings that aren't the most bullish. However, mostly clear skies and light winds should lead to decent radiational cooling. Therefore, opted to add patchy fog for tonight into Sunday morning that dissipates from northwest to southeast.

DISCUSSION

Issued at 145 PM CDT Sat Sep 26 2026

Currently a cold front is sweeping through the state west to east, clearing out the low stratus clouds. Behind the front winds are gusting up to 30mph. This trend will continue through the evening. In the low stratus mist and sprinkles are falling, reducing visibilities at times. Aloft a large broad trough has formed across the Pacific Northwest. The rest of this weekend will be in the 60s to lower 70s. That broad trough will bring southwest flow back into the state Sunday, leading to showers and thunderstorms beginning Sunday evening south of the interstate. After sunset, the chances will increase as a disturbance from the Rockies forms a surface low and moves into the Dakotas.

Showers and thunderstorms will continue through Monday as a shortwave and front move in behind the low. There is a chance for thunderstorms as there will be 200-500 J/kg of MUCAPE available Sunday night with 40-50kts of shear. Severe storms cannot be ruled out Sunday with a potential low level jet across the Dakotas, but as of now it remains a very low risk. Monday some models have a small axis of 1000 J/kg of MUCAPE but others don't, so again low confidence in severe storms Monday, but not zero. Monday with the surface low in northern South Dakota cold air funnels or even a legit tornado could maybe be possible but it would be a very conditional risk. Through these 3 period there are medium to high chances of at least 1 inch of rain.

The rest of the week zonal flow takes over the northern CONUS, keeping temperatures seasonal in the mid 60s. Afternoon humidity values will lower back under 50 percent. Overnight lows will hang around the mid 40s and possibly upper 30s in the far north. Looking towards next weekend another shortwave could move in, lowering highs into the 50s with a chance of rain.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 156 AM CDT Sun Sep 27 2026

Patchy dense fog will impact areas from around KBIS to KJMS overnight. The fog should lift by sunrise as light winds become west to northwest. VFR conditions are otherwise expected through the forecast period. A few showers are possible across southern parts of the state from time to time throughout the forecast period, with much higher chances for showers and thunderstorms developing after 06Z Monday. Light and variable winds are expected for most areas through Sunday afternoon.

BIS WATCHES/WARNINGS/ADVISORIES

None.