textproduct: Bismarck

KEY MESSAGES

- Above normal temperatures for the most part through the middle of this week, with medium to high chances for showers and isolated thunderstorms late tonight through Monday night.

- Low chances for a wintry mix Monday morning and again Monday night into Tuesday morning across the far north.

- Significant cool down possible for the end of this week, with medium chances for both rain and snow.

UPDATE

Issued at 1058 PM CDT Sun Apr 12 2026

No major changes are needed for this update. Current conditions and trends have been blended into the forecast. Some light rain showers are now moving into the southwest corner of the state. There is still a small chance for a thunderstorm later tonight in the southwest, spreading northeast into central North Dakota Monday morning. Severe weather is not expected through Monday morning, but we are still evaluating a potential for strong to possibly severe thunderstorms in far southwest North Dakota late Monday afternoon. 00Z CAMs have a more consolidated updraft helicity footprint (using HREF neighborhood probabilities) that touches the ND/SD border.

UPDATE Issued at 728 PM CDT Sun Apr 12 2026

The chance for a thunderstorm developing in the James River Valley appears to have ended, as satellite imagery no longer shows agitated cumulus in the area of concern, or anywhere across our forecast area for that matter. Current conditions and trends along with the latest ensemble guidance have been blended into the forecast for this update.

Several CAMs have been advertising a complex of stronger thunderstorms moving into southwest North Dakota late Monday afternoon ahead of a stronger vort max ejecting off the Bighorn Mountains. Projected CAPE does not appear to be overly impressive and is forecast to be decreasing over time, but there is no shortage of effective bulk shear. A couple of CAMs, most notably the 18Z HRRR, have actually generated UH tracks whose strength would be sufficient for a severe storm. We will wait and see if these trends hold in the 00Z suite of CAMs before introducing strong thunderstorms to our messaging.

DISCUSSION

Issued at 254 PM CDT Sun Apr 12 2026

This afternoon, the synoptic pattern was characterized by a closed low and attendant trough moving onshore over the western CONUS, with broadly west to southwest flow across the Dakotas. An embedded shortwave was moving into northern Minnesota, in line with a surface low analyzed in the same general area that was producing showers and thunderstorms. This activity moved through the forecast area earlier this morning and has since exited, with a mild and pleasant albeit breezy day across western and central North Dakota. Plenty of sunshine with afternoon high temperatures around 60 F north to the mid 70s south.

A cold front is beginning to move into northern North Dakota, demarked by a line of low stratus and a shift to more northerly winds. This front will continue to sink south through this afternoon and evening, with a low chance of an isolated shower or thunderstorm in the James River Valley area, but otherwise the main impact will be cooler air filtering into the state behind the front.

As the aforementioned western CONUS trough begins to split, the northern stream is progged to eject a shortwave over the Northern Rockies late tonight through Monday, with more widespread precipitation chances beginning tonight in southwest North Dakota. Deterministic guidance is advertising up to a couple hundred J/kg of instability available while bulk shear is much stronger, so can't rule out isolated thunderstorms and potentially some small hail at the most. Precipitation chances increase further on Monday, especially across western North Dakota where they peak at 60 to 80 percent. Latest NBM has a medium chance of at least 0.25" of QPF for much of western and north central North Dakota over this period. Late tonight into Monday morning there is also a low potential for a wintry mix across far northern North Dakota, with morning lows around freezing and a warm nose aloft that could potentially lead to freezing rain, although whether this occurs or if precipitation falls as snow, not expecting enough to make much of an impact. There could also be some patchy fog tonight into Monday morning across the entire forecast area, although high-res guidance implies this might not be long-lived at any one location.

Highs on Monday will range from the lower 40s north to the upper 50s far southwest. Widespread low to medium chances for rain continues through Monday night before conditions start to improve on Tuesday as the shortwave exits to our east. Shortly after, the western trough consolidates more and brings additional precipitation chances south of the forecast area, with Tuesday and Wednesday looking dry overall. Highs rebound relatively quickly, with highs in the mid 50s to mid 60s on Tuesday, and the lower 60s to lower 70s on Wednesday.

Bigger changes emerge to end the work week, as ensemble guidance continues to advertise a potent trough dropping into the Pacific NW before tracking into the Northern Plains. Confidence is highest in this system bringing widespread precipitation chances Thursday and Friday, along with cooler temperatures to start the weekend. The uncertainty lies in the speed of the system, with large temperature spread in NBM percentiles signaling a variety of solutions regarding when the front comes through. This will influence p-types which is the other main area of uncertainty in the forecast. NBM 5.0 snow probabilities have decreased quite notably from this time yesterday, although overall precipitation probabilities are still broadly 30 to 50 percent. Expect both Thursday and Friday to be windy ahead of and behind the main cold front associated with the upper wave, although ECMWF EFI isn't showing anything anomalous at this point. There is moderate confidence in temperatures warming up to around normal by the end of the weekend, but overall a cool and cloudy end to this week is expected.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 1058 PM CDT Sun Apr 12 2026

Low ceilings are expected to expand over all of western and central North Dakota by Monday morning, spreading southwestward through the night. Mostly expecting IFR ceilings through Monday morning, but southern North Dakota could see a period of LIFR, and the northwest is more likely to remain at MVFR. MVFR ceilings are then likely to prevail at all terminals through Monday afternoon, with pockets of IFR possible at times.

An area of scattered showers will move into southwest North Dakota late this evening and slowly lift northeastward overnight and through the day Monday. Confidence in persistent rain on Monday is highest across the north. The rain could cause MVFR visibility at times. There could also be patchy fog across western and central North Dakota tonight into Monday morning, with the highest concentration expected south of KDIK, KBIS, and KJMS. Near the end of the forecast period, a complex of thunderstorms could enter southwest North Dakota.

Winds will turn from northerly to easterly tonight into Monday, sustained around 10-15 kts.

BIS WATCHES/WARNINGS/ADVISORIES

None.