998 FXUS63 KBIS 150644 AFDBISArea Forecast Discussion National Weather Service Bismarck ND 144 AM CDT Mon Sep 15 2025
.KEY MESSAGES...
- Dense fog in northwest North Dakota through mid Monday morning.
- Shower and thunderstorm chances continue through much of the week.
- Highs mostly in the 70s through Tuesday, then cooling into the 60s by the end of the work week.
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.UPDATE... Issued at 142 AM CDT Mon Sep 15 2025
Observed visibility from Crosby to Tioga has consistently been at zero. The fog could briefly lift if a band of rain moves over the area, but otherwise do not see any indication of improvement until after sunrise. A Dense Fog Advisory has been issued for the 4 northwest counties until 10 AM CDT.
Latest RAP analysis shows a closed 500 mb low over Hettinger, embedded in a negatively-tilted trough with a major axis from northeast Montana to south central South Dakota. Bands of showers are generally lifting north-northwest across the western third of the state at the time of this writing, and there has recently been only very infrequent lightning observed in Grant County. The broader area of rain is expected to begin lifting to the north- northeast by early Monday morning, focusing along the Highway 83 corridor from Minot to Bismarck.
UPDATE Issued at 936 PM CDT Sun Sep 14 2025
Conditions have tamed down greatly over the area as most of the convection has lifted into Manitoba/Saskatchewan. Some showers continue to linger over the area, which will be the trend through the night. With that said, can not rule out a clap or two of thunder, but expect any storm to remain tame. Only possible concern is if a heavier shower were to linger over an area of central North Dakota that received heavy rain this past afternoon/evening. Otherwise, only other concern would be the possibility of some fog given the moist lower levels and light winds given the surface low lifting in. Have broad-brushed patchy fog in for now for most areas and will see how this evolves going into the overnight.
UPDATE Issued at 723 PM CDT Sun Sep 14 2025
Thunderstorms continue to lift through central North Dakota into the James River Valley. Current tornadic storm lifting through McHenry County continues to run right along a gradient of around 30kts of 0-3km shear, which has been the general trend through this event. A line of storms has also blossomed on the southern end of an area of elevated instability, moving into a more unstable airmass. So far the main possible threat with these storms would be wind, though brief heavy rain fell in Jamestown leading to some street flooding. The expected general trend with this whole system is to continue to lift northward, and also expect a downward trend with the loss of daytime heating, especially on the eastern storms.
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.DISCUSSION... Issued at 231 PM CDT Sun Sep 14 2025
Surface low now lifting northward, centered between Pierre and Mobridge, SD, with warm front wrapping into the north side of the low. Broad area of showers and storms have developed over south central into southwest North Dakota. In this vicinity, more low-level SRH rich air in the vicinity of the warm front will bring a tornadic threat. This has been confirmed by multiple tornadoes that have already occurred over far south central North Dakota. There also is a limited large hail/wind threat. Another great concern given the moisture rich environment is heavy rain, thus the potential for flooding. The threat for the severe weather continues into this evening before dissipating.
System will meander north through the night. Models still show a bit of timing uncertainty with the departure of the low into Canada on Monday, now generally sometime in the afternoon/early evening. This keeps high chances for showers but comparatively lower chances for thunderstorms in the forecast on Monday, decreasing from south to north in the afternoon through the evening. Not long after the departure of the low late Monday, another wave deepening over the Northern Rockies will begin sending DCVA into the region on Tuesday, which keeps a 20 to 40 percent chance of rain in the forecast. Guidance then shows another shortwave digging down from Canada on Wednesday. This wave is likely to bring a cooler air mass into the region, which may hold through the end of the week as the wave interacts with the other aforementioned wave and meanders around the Upper Midwest. The NBM maintains a 30 percent chance of rain on Wednesday, followed by only a 20 percent chance Thursday through Saturday.
For Monday and Tuesday, high temperatures are mostly expected to be in the 70s, though parts of southwest and south central North Dakota could stay in the mid to upper 60s should it rain most of the day. Ensembles then show a distinct cool down for the second half of the week, with highs mostly in the 60s Thursday through Saturday. Forecast lows tonight remain closer to summertime values of mid 50s to lower 60s, then gradually cool to around 45 to 50 for the second half of the week.
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.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 142 AM CDT Mon Sep 15 2025
Showers with an occasional thunderstorm will continue across the western half of North Dakota overnight, slowly lifting north- northeast through Monday afternoon. Rain could reduce visibility as low as IFR levels at times. Dense fog and LIFR ceilings have developed in northwest North Dakota. These conditions may reach KXWA early Monday morning. MVFR to IFR ceilings are expected across central North Dakota overnight. The low ceilings may swing toward KJMS Monday morning before lifting northward Monday afternoon. Central North Dakota will see southwesterly winds increase to around 10-15 kts Monday afternoon, with northwesterly winds around 10 kts farther west.
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.BIS WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 10 AM CDT this morning for NDZ001-002- 009-010.
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UPDATE...Hollan/JJS DISCUSSION...Anglin/Hollan/JJS AVIATION...Hollan
NWS BIS Office Area Forecast Discussion