textproduct: Bismarck

KEY MESSAGES

- Scattered to numerous showers across much of western and central North Dakota this morning, becoming widespread and expanding eastward through the afternoon and evening. A few afternoon thunderstorms could produce heavy downpours.

- Cooler again today, with highs mostly in the lower 50s to lower 60s.

- 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 900 AM CDT Fri May 22 2026

Moderate radar returns are found over portions of western and central North Dakota at the time of this mid morning update. We're starting to see some more scattered, pop-up showers develop over the north central, slightly ahead of schedule. The expectation is that these showers will continue to fill in through the morning into the afternoon. With this earlier development, will need to monitor for isolated rumbles of thunder over the next few hours, though the cap is still progged to remain in place through at least the late morning. The next surge of precipitation, associated with a stacked low analyzed over southern South Dakota at this time, is also anticipated to slide in across central North Dakota later today.

UPDATE Issued at 645 AM CDT Fri May 22 2026

Overall, the rain is unfolding as expected early this morning. Minimal changes are needed for this update, and were based on observed and latest modeled trends. This did include removing the mention of thunder until late morning.

DISCUSSION

Issued at 432 AM CDT Fri May 22 2026

Early morning upper air analysis shows two closed upper lows bookending a trough axis from southern Saskatchewan to eastern Wyoming. At the surface, an inverted trough axis lies across the western Dakotas. The inverted trough has been and will continue to be the broad focal area for scattered to numerous showers through the morning. There is a relative lull in shower activity at the time of this writing, but that should quickly change as the low at the base of the upper trough spins northeastward into western South Dakota, pushing the current batch of rain over the Black Hills northward. The closed low will continue spinning northeastward throughout the day, dragging a surface low into southeast South Dakota this afternoon. Strong synoptic scale forcing from mid level DCVA and low level warm air advection to the north and northeast of the nearly-stacked low pressure system is expected to bring a large shield of mostly stratiform rain across the eastern two thirds of the state from south to north later this morning through this evening. Most of the state outside of the far west is favored to receive around a quarter to half inch of rain through tonight, which is in addition to what has already fallen since yesterday. The James River Valley has higher odds for exceeding half an inch, and even medium chances for three quarters to one inch of rain. In contrast, there is a potential for a narrow corridor of lower rain amounts over central North Dakota due to an area of diffluence in the low level wind field, which may not allow the area of rain associated with the inverted surface trough to fully adhere to the northward moving stratiform rain shield. This inverted dry slot footprint is quite prominent in the HREF probability- matched mean QPF, which places it from the Turtle Mountains to eastern Morton County. One final note about the rain forecast for today is that there is another potential for afternoon thunderstorms, mainly along the inverted trough axis. The risk for stronger storms appears lower than yesterday, but any training or nearly-stationary convection would produce locally higher rain amounts.

Regardless of rain amounts, it will be a cool and cloudy day for most of the state, with highs mostly in the 50s. Lower 60s could be achieved along the Montana border if clouds clear early enough, and also near the Turtle Mountains where rain-cooled air and thicker cloud cover may not arrive until after peak heating. The rain should depart from southwest to northeast this evening through tonight, leaving behind a potentially favorable setup for fog formation. Forecast lows tonight are mostly in the upper 30s to mid 40s. There could be a few spots in southwest North Dakota that dip to near freezing, but as of this writing, lows in the mid 30s or colder are not expected to be widespread enough to warrant a Frost Advisory.

Saturday will mark the beginning of a substantial warming trend through the holiday weekend, with the NBM projecting highs in the upper 60s to mid 70s on Saturday, upper 70s to mid 80s on Sunday, and mid 80s to lower 90s on Memorial Day. Flow aloft remains cyclonic on Saturday as the departing mid/upper level low stalls over southern Manitoba. This could allow a few afternoon showers and thunderstorms to develop. Forecast CAPE and shear parameters do not appear supportive of severe convection on Saturday, but a couple of CAMs do simulate a few stronger storms. The highest probability for isolated thunderstorms is in north central North Dakota, but is still no greater than 20 percent. On Sunday, flow aloft turns quasi- zonal as a ridge building over the Four Corners region begins to push mid level height rises into the Northern Plains. There is uncertainty on whether an embedded shortwave could briefly interrupt the height rises and initiate convection Sunday afternoon and evening. In the 00 UTC suite of guidance, this feature is only pronounced in the deterministic GFS and a very low-membership ensemble cluster, so we will continue to advertise dry weather on Sunday. Confidence in dry weather is even higher on Memorial Day as the upper ridge becomes fully established over the Northern Plains.

A very strong upper level low/trough will dig into the western CONUS by Tuesday, further amplifying the central CONUS ridge and potentially setting up an omega-blocking pattern through the end of May. Ensemble guidance tends to favor the Northern Plains lying under the southerly flow aloft pattern between the upstream trough and downstream ridge, but in closer vicinity to the ridge. This renders low predictability for any shower and thunderstorm chances, although the NBM does have a period of 30-40 percent PoPs late Wednesday through Thursday. Interestingly, there is also a weak signal in GEFS-based machine learning guidance for a low-end severe thunderstorm risk next week. While moisture and CAPE will certainly be at the highest they've been so far this season, the shear forecast remains highly uncertain. Higher confidence aspects of the forecast for next week under the favored pattern are temperatures remaining above normal and an increase in southerly winds, both of which are beginning to be highlighted by the ECMWF EFI products.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 900 AM CDT Fri May 22 2026

Scattered to numerous showers will continue across much of the western half of the state through this afternoon. Meanwhile, a separate area of rain will expand northward from South Dakota into the eastern half of the state later this morning and afternoon. The widespread rain is forecast to diminish from southwest to northeast this evening into tonight. Expect periods of MVFR to IFR visibility with heavier showers and more persistent areas of rain. A low chance of thunderstorms returns to central North Dakota this afternoon.

Ceilings are forecast to fall to MVFR levels from southwest North Dakota to between KXWA and KMOT by mid morning, with IFR possible at KDIK. By late morning, low ceilings should begin expanding over KBIS (prevailing MVFR) and KJMS (MVFR lowering to IFR). KMOT is likely to maintain a VFR ceiling until MVFR arrives this evening. Meanwhile, KXWA could remain at VFR through the forecast period. Low ceilings are forecast to prevail over much of central and eastern North Dakota through tonight, ranging from MVFR from KMOT to KBIS to possibly as low as LIFR at KJMS. There is also a potential for fog developing later tonight across the western half of the state.

Winds today will generally be northerly around 5-10 kts in western North Dakota and easterly around 10-15 kts in central and eastern North Dakota. Light and variable winds are then expected for the western half of the state tonight, with a 10 kt wind turning from easterly to northwesterly at KJMS.

BIS WATCHES/WARNINGS/ADVISORIES

None.