textproduct: Bismarck

KEY MESSAGES

- Isolated thunderstorms this morning and again this afternoon through tonight. The threat for severe weather is low.

- Above normal temperatures for the most part through the middle of this week, with additional medium to high chances for rain with isolated thunderstorms on Monday.

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

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

UPDATE

Issued at 1005 AM CDT Sun Apr 12 2026

Surface analysis shows low centered in southeast North Dakota, with showers and thunderstorms on the northwest side across the James River Valley. A few of the thunderstorms have gotten somewhat strong, with pea-sized hail observed at the office this morning as they passed through. As the surface low has moved through, fog has been diminishing rather quickly, with only a few isolated spots in the southern James River Valley showing any real reduced visibility. We did let the Dense Fog Advisory expire as planned, but could still see some isolated patchy fog through the rest of the morning. No big changes to the gridded forecast with this update.

UPDATE Issued at 645 AM CDT Sun Apr 12 2026

Dense fog continues to be reported this morning, thus the Dense Fog Advisory remains in effect for much of central and eastern North Dakota. Surface low also bringing showers and isolated thunderstorms this morning to western and now into some central portions. Look for this low and these showers to push eastward through the morning. This could also help lift fog throughout the morning. Overall the forecast remains on track.

DISCUSSION

Issued at 400 AM CDT Sun Apr 12 2026

Surface low will continue to bring showers and thunderstorms across the forecast area this morning. Meanwhile abundant low level moisture in the central and east will continue dense fog this morning until the surface low pushes this eastward. Thus the Dense Fog Advisory will remain as is. A somewhat breezy northwest flow then develops behind this surface low today. Cold front still looks delayed thus temperatures will again be warm today, and used NBM50th for highs with widespread 60s and 70s. This brings some lower RH values this afternoon, although winds should remain below critical fire weather conditions. Weak instability ahead of an advancing cold front could bring some isolated thunderstorms to central portions later this afternoon into this evening. Shear is a bit more increased today, although instability remains low. If any organized storms can develop then some small hail and gusty winds are possible. This mentioned front then combines with a mid level shortwave tonight through Monday bringing better chances for showers and thunderstorms. Some cooler air in the north could provide for a wintry mix in the north Monday morning, although impacts from snow or even brief freezing rain should be limited. Depending on timing of the upper level wave, some fog could return tonight into Monday morning. Added in some patchy fog mention to account for this possibility. Highs on Monday will be much cooler given the cold front passage with 40s in the north to the 50s in the south. Winds will become easterly on Monday. Rain showers with some wintry mix in the north could then linger Monday night into early Tuesday morning. Lows will continue to cool and generally be in the 30s. Depending on precipitation timing, fog is again possible Monday night into Tuesday morning. Given the uncertainty left out mention of fog during this time period.

Zonal flow for Tuesday and Wednesday will bring warming temperatures and generally dry conditions. Highs in the 60s to perhaps lower 70s will be found each day. Some lower RH values may return on Wednesday, although winds look to be below critical fire weather criteria. Lows at night mid week will also be mild and generally in the 30s and 40s. Clusters still showing a decent trough moving through later in the upcoming work week. High confidence this will bring cooler temperatures as indicated by the NBM temperatures spreads. Less confidence in the chances for rain and accumulating snow during this time period. Clusters with Canadian and European ensembles showing more snow than clusters with GFS ensembles. The two scenarios are about equally split at this time. NBM chances for over an inch of snow in a 24 hour period to end the week are currently at around 10 to 30%. The split wave nature of this trough could also limit precipitation and potential snowfall. Overall a pattern shift could be found to end the week, along with the chances for accumulating snow which will be worth monitoring going forward.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 645 AM CDT Sun Apr 12 2026

IFR to LIFR conditions will continue with low clouds and fog across central and eastern portions through mid morning today. Meanwhile showers and isolated thunderstorms will push from west to east this morning, perhaps bringing some MVFR conditions. Widespread VFR conditions are then expected today, although some lingering MVFR clouds could be found in the east, including KJMS. A few isolated thunderstorms may also develop later this afternoon. Tonight, low clouds and perhaps some fog may return. For now placed in MVFR to IFR ceilings at most TAF sites. Chances for showers and thunderstorms may also return this evening through tonight. Confidence is only moderate for these showers tonight, thus used PROB30 groups for some western TAF sites. Light and variable winds will turn west- northwest today, then becoming easterly tonight.

BIS WATCHES/WARNINGS/ADVISORIES

None.