textproduct: Bismarck

KEY MESSAGES

- Lows tonight into Tuesday morning dip into the upper 20s to lower 30s. Freeze Warnings and Frost Advisories have been issued. Cold temperatures again possible Tuesday night/Wednesday morning, mainly east.

- Isolated showers remain possible overnight west and south central. Patchy fog possible in the far northwest.

- Unsettled weather pattern develops mid to end of the week. Greatest and most widespread chances (about 30 to 60 percent) come Thursday into Friday.

UPDATE

Issued at 1025 PM CDT Mon May 18 2026

Showers have generally exited to the east of western and central North Dakota at the time of this mid evening update. Weak radar returns linger over portions of central North Dakota, though with such poor forcing only sprinkles are anticipated at this time. Otherwise, with clearing skies found upstream to the northwest of the forecast area, did opt to add some patchy fog to northwest for the early to mid morning.

UPDATE Issued at 630 PM CDT Mon May 18 2026

Light rain continues across portions of south central North Dakota at the time of this early evening update, with sporadic reports of drizzle also found further to the west. Precpitation is generally expected diminish from west to east through the evening. More isolated showers will be possible across the west and south central overnight, though additional accumulation is would be light. Have tweaked the PoP grids in line with the latest CAM guidance. Will also need to evaluate the potential for additional fog development tonight, especially across the northwest where low stratus is expected to diminish the quickest. Overall, the forecast remains in good shape at this time.

DISCUSSION

Issued at 223 PM CDT Mon May 18 2026

Current surface analysis places low over the upper midwest with notable frontal boundary stretching to the southwest through the central plains. High remains over southern Saskatchewan into central Montana. Upper level analysis places trough over Saskatchewan southward towards the central Rockies. Southeast flow over our area with some embedded short waves is resulting in broad shower activity over much of South Dakota into southeast/south central North Dakota.

For tonight, ongoing showers will continue into this evening before departing to the east/northeast. In the meantime, surface high settles into the area, mainly western locations, with cool air continuing to slide in. This will result in sub freezing temperatures over parts of western and north central North Dakota, therefore a Freeze Warning has been issued. Further east, confidence is a little lower as to how cold it will get given the persistant cloud cover. With that said, lows look to dip close to or reach freezing, so have decided to go with a Frost Advisory for that area even though technically "frost" will not form, but sensitive plants could be damaged, especially if temperatures are a degree or two lower than forecast.

Trough pushes east early Tuesday, with a low amplitude ridge passing over for Tuesday into Wednesday. Expect a gradual warm- up for high temperatures, but Tuesday night may see some freezing lows, mainly over our east given the high passing over and clearing skies.

Next trough digs in over the western CONUS on Thursday with our flow shifting southwesterly before the system closes off and ejects to the northeast to close out the week. Greatest chances for precipitation come Thursday into Friday (about 30 to 60 percent chance). Warming trend expected going into the weekend with NBM temperature spreads being quite confident in seeing well above average temperatures by late weekend.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 1025 PM CDT Mon May 18 2026

Widespread MVFR and sporadic IFR ceilings are found at all terminals as low stratus persists across the region. Rain showers continues across the south central, occasionally promoting the aforementioned IFR ceilings and some MVFR visibility reductions. Ceilings are expected to generally improve through the evening across the far west, with also generally diminishing through this period. Ceilings are then expected to improve across the east overnight through Tuesday morning. North winds will diminish through the evening, becoming light overnight through Tuesday morning as they turn more northwesterly. Gusty winds are then expected to develop in the south central late Tuesday morning through the afternoon, with sustained speeds around 15 knots and gusts up to 25 knots at times.

BIS WATCHES/WARNINGS/ADVISORIES

Freeze Warning until 9 AM CDT /8 AM MDT/ Tuesday for NDZ001>005-009-010-012-017>020-022-031>033-040-041-043-044- 055>059. Frost Advisory until 9 AM CDT /8 AM MDT/ Tuesday for NDZ013- 023-025-035>037-042-046>048-050-051-060>062.