979
FXUS63 KBIS 311154
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
654 AM CDT Sat Oct 31 2026

.KEY MESSAGES...

- Cloudy and seasonably mild this weekend, with low chances for
  light rain, drizzle, and dense fog from time-to-time.

- High chances for rain across most of the state Sunday night
  through Monday night. Rainfall could exceed 1 inch (60 to 90
  percent chance) in the southern James River Valley.

- Near to above normal temperatures and drier weather favored
  mid to late next week.

&&

.UPDATE...
Issued at 653 AM CDT Sat Oct 31 2026

Light rain and drizzle continue to be more limited than what
had been anticipated, although some very light drizzle or mist
is likely falling from around the Killdeer Mountains to the
southern James River Valley as indicated by 5-6 mile visibility
in surface observations. The forecast has been adjusted
accordingly. Within the last hour, areas of dense fog have
developed in the southwest corner of the state. A Special
Weather Statement has been issued to address this.


&&

.DISCUSSION...
Issued at 405 AM CDT Sat Oct 31 2026

A negatively-tilted upper level ridge extends from Alberta/
Saskatchewan to Georgia/Florida early this morning. The ridge
axis cuts through the Dakotas over a veering low level wind
profile. Low level warm air and moisture advection will persist
through the day today as underlying surface flow remains
easterly between a surface ridge axis extending northwest from
the Great Lakes and a lee cyclone over Wyoming. Low stratus is
forecast to expand northward across the state this morning and
afternoon, and the depth of the near-surface saturated layer may
be sufficient for areas of mist or drizzle. Isolated to
scattered showers could also develop over central and eastern
North Dakota today ahead of 700 mb DCVA, but subsidence aloft
could be a deterrent. Because of the extensive cloud cover, the
high temperature forecast for today was lowered closer to the
25th percentile of the NBM distribution, which gives upper 40s
north central to mid 50s south.

Most of the state will remain under a deeper low level layer of
saturation tonight into Sunday, which may continue to promote
areas of mist and drizzle. Models that simulate visibility would
indicate widespread dense fog tonight into Sunday, but this
seems more like a low stratus episode where ceilings could lower
to the surface along areas of higher terrain. Low to medium
chances for light rain also remain in the forecast tonight into
Sunday, becoming more focused over northwest North Dakota as a
mid level shortwave drifts through the area. Temperatures will
remain mild overnight, with near-record warm lows mostly in the
mid 40s to lower 50s. Sunday should be slightly warmer than
today, but still closer to the NBM 25th percentile highs of
lower 50s northwest to lower 60s south central and southeast
given an overcast sky prevailing for most areas.

A deep upper level trough will begin crossing the Rockies
Sunday night, inducing lee cyclogenesis over Colorado.
Meanwhile, a northern stream wave is projected to dig into the
southern Canadian prairie provinces Monday morning and interact
with the Colorado low and its parent upper trough. This sets
the stage for a widespread rain event that will impact most,
but perhaps not all of North Dakota. The highest chances for
rain (90 to 100 percent) enter southwest North Dakota late
Sunday night and migrate eastward through the day Monday,
departing to the east Monday night. Lower chances for lighter
rain (20 to 40 percent) remain in the forecast for central and
eastern North Dakota through Tuesday, with higher- membership
ensemble clusters favoring a slower departure of rain. Ensemble
mean QPF and threshold probabilities are lowest over north
central North Dakota and increase in all southward facing
directions. The highest amounts/chances by far are in southeast
North Dakota, but there is a secondary local maximum from
southeast Montana into southwest North Dakota. NBM calibrated
QPF output remains higher than that of raw global ensembles,
especially at higher thresholds. But even global ensembles are
now showing medium chances for exceeding 2 inches of rain in
the southern James River Valley. In addition, the ECMWF EFI and
shift-of-tails products do support an anomalously high QPF
event, so the NBM calibrated QPF may not be overly aggressive.
Temperatures will remain above freezing through the duration of
the precipitation event. Sunday night lows are forecast to
remain in the 40s, followed by mid 40s to mid 50s for highs on
Monday. Monday night will be colder than Sunday night, but
forecast low temperatures below freezing are only anticipated
if and/or where precipitation ends. Lastly, the passage of the
surface low to the south and east will likely bring a period of
strong northeast to northwest winds across southern North
Dakota Monday through Monday night, with medium chances of
winds reaching advisory criteria.

Ensemble consensus broadly supports upper level ridging over
the central CONUS for the middle of next week, but
deterministic guidance implies the ridge could be interrupted
by lower-amplitude shortwaves that are being washed out in mean
height fields due to timing and location uncertainty.
Significant ensemble spread in the synoptic pattern emerges by
the end of next week, but the jet stream is favored to remain
south of the Northern Plains. The NBM maintains near to above
normal temperatures and a dry forecast from mid to late next
week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 653 AM CDT Sat Oct 31 2026

Low ceilings will continue spreading across the state from
south to north this morning, settling at mostly LIFR across the
south to MVFR across the north by this afternoon. Improvement to
IFR is possible in southern North Dakota this afternoon before
LIFR ceilings cover the whole state tonight. Periods of mist and
drizzle are possible under the low clouds, which may reduce
visibility to MVFR or IFR levels at times. Some light rain
showers are also possible, mainly near KJMS this afternoon and
from KXWA to KMOT this evening through tonight. But the rain
will not cause categorical restrictions lower than those caused
by ceilings. Winds will remain easterly to southeasterly around
5-10 kts through the forecast period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Hollan
DISCUSSION...Hollan
AVIATION...Hollan