textproduct: Bismarck

KEY MESSAGES

- Showers ending from southwest to northeast tonight.

- Areas of dense fog across western North Dakota late tonight into Saturday morning.

- Temperatures warm to well above normal for the first half of next week, with highs mostly in the 80s to lower 90s. Tuesday and Wednesday could be windy.

- Other than a few isolated showers or thunderstorms on Saturday, the holiday weekend is expected to be dry.

UPDATE

Issued at 203 AM CDT Sat May 23 2026

Quick update to issue a Dense Fog Advisory for much of western North Dakota. Latest satellite trends show fog becoming more established along the corridor mentioned in the previous update discussion, and models are in strong agreement that this fog will persist through early Saturday morning. A few counties, such as Divide, Golden Valley, and Bowman, were preliminarily left out of the advisory as it was hard to justify their inclusion with no observable fog within or even near those counties at this time.

UPDATE Issued at 132 AM CDT Sat May 23 2026

At 1 AM CDT, surface low pressure was analyzed between Aberdeen and Sisseton, SD, and the upper low was spinning northeastward toward Grand Forks. Persistent rain continues mainly east of Highway 83 and north of Highway 200, with isolated to scattered showers roaming across the James River Valley. Rain should continue to diminish from southwest to northeast through the rest of tonight into early Saturday morning.

The main concern for the short term period is quickly becoming dense fog. Surface observations and satellite imagery show a narrow corridor of dense fog over western North Dakota that includes Tioga, Watford City, Killdeer, Dickinson, and Hettinger. Glen Ullin has also recently dropped below a quarter mile visibility right up against the western edge of the stratus. A Special Weather Statement has been issued to address the fog, but would not be surprised to see it later elevate to needing a Dense Fog Advisory. Will also need to monitor southeast parts of our forecast area for dense fog development, which are in close proximity to the surface low.

UPDATE Issued at 923 PM CDT Fri May 22 2026

A few thunderstorms did wind up occurring over parts of the north central since the last update. However, a localized pocket of slightly higher instability has decreased as the sun sets, and as such, lightning hasn't been observed in the past half hour or so. While a rogue lightning strike isn't entirely out of the question, thunderstorm potential for the rest of the night is low. Otherwise, adjusted PoPs and sky cover a bit to match the latest satellite and radar trends.

UPDATE Issued at 646 PM CDT Fri May 22 2026

Widespread showers continue across much of central and eastern North Dakota, though have mostly ended over western North Dakota. A few heavier and more isolated showers have developed mainly in the north central west of the main precipitation shield. While there were a few strikes of lightning earlier, these have generally remained thunder free so far. Still, a few of these showers could develop into thunderstorms and produce brief heavy downpours over the next couple hours. Showers will gradually end from southwest to northeast through the night tonight.

DISCUSSION

Issued at 210 PM CDT Fri May 22 2026

Aloft, a positively tilted trough axis is draped between two low centers, one over southern Saskatchewan and one over eastern North Dakota. At the surface, a stacked low pressure system is lofting across western and central North Dakota this afternoon. Widespread showers associated with the broad precpitation shield extending off this low is found across portions of western and much of central North Dakota. CAMs continue to advertise the development of thunderstorms along an inverted surface trough extended across the north central later this afternoon, with model MUCAPE values generally around 500 - 750 J/KG. While the potential for server weather remains very low, the potential for redeveloping storms as the whole system lifts further north invites the potential for locally heavy rainfall. In general, additional rainfall totals of around 0.25" to 0.50" is forecast through the afternoon and evening, a period through which precpitation is expected to diminish from southwest to northeast as the inciting low pressure system moves off into southern Canada. Otherwise for today, cooler highs broadly in the 50s are anticipated with the prevalent cloud cover, though some portions along the ND/SD border could approach the lower 60s by the mid afternoon. Overnight low are forecast to drop mainly into the upper 30s to lower 40s, though diminishing cloud cover across the west late tonight into early Saturday could allow some areas in the southwest to drop into the lower to mid 30s. Notably, with the fresh precpitation and light winds expected overnight, patchy fog may develop Saturday morning behind the retreating edge of the cloud deck as it moves off to the east.

Cyclonic flow is expected over the northern Plains on Saturday as the merger between the two upper level lows stalls over the southern Canadian Prairies through the early weekend. With such a pattern, near daily low chances chances for isolated showers or thunderstorms will be possible, mainly in the afternoon and evening hours. Otherwise, mainly dry conditions are expected on Saturday. With the eventual displacement of the merged lows further off to the northeast, and with an building ridge moving in across the Great Plains this weekend, North Dakota is expected to fall into a a warming trend through the first half of the coming week. With this, highs mainly from the 60s and 70s on Saturday are expected to rise up into the the 80s and lower 90s by Monday and Tuesday. Mainly dry conditions can similarly be expected throughout this period, though isolated showers or storms are not impossible Sunday afternoon as flow turns zonal ahead of the building ridge. Amplification of the building ridge is then expected by late Tuesday into Wednesday, as a robust Pacific trough/closed low is progged to make landfall in the western CONUS. The ensemble seems to have fairly decent agreement in at least some displacement of the ridge further to the east by the incoming trough. Cluster analysis reveals that the ensemble is split between two broad scenarios depending on how far east the ridge is displaced. In the first scenario, an open wave nudges the ridge slightly to the east, allowing for low chances (10 to 30 percent) for precpitation across the west some time Wednesday through the end of the workweek. Scenario 2 advertises a more robust closed low bumping the ridge much further eastward, allowing for similarly low chances for precpitation across much of the west and portions of central North Dakota. In either scenario, overall rain totals are anticipated to be light at this time, with only a low chance (30 percent) for portions of the west to exceed 0.25" through this period. Notably, the CSU machine learning algorithm does paint low chances for severe hazards on day 5(Wednesday through Thursday), so we'll need to watch this period over the next few days.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 132 AM CDT Sat May 23 2026

Rain will continue to end from southwest to northeast through the night. Low ceilings will prevail across central and eastern North Dakota into Saturday morning, primarily at IFR to LIFR levels. Meanwhile, dense fog is developing over parts of western North Dakota, including at KDIK. The dense fog could expand across much of the western half of the state before dissipating mid Saturday morning. After the fog lifts and ceilings scatter and rise by early Saturday afternoon, VFR conditions are expected through the rest of the forecast period. A few isolated showers or thunderstorms could develop across central North Dakota Saturday afternoon and early evening. Winds will become westerly to northwesterly around 10 kts on Saturday.

BIS WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 10 AM CDT /9 AM MDT/ this morning for NDZ002-009-010-017-018-032-033-040>042-044-055-059.