150
FXUS63 KBIS 090917
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
417 AM CDT Thu Oct 9 2025

.KEY MESSAGES...

- Mild and dry weather continues today through Friday.

- Sub-freezing temperatures possible across parts of western
  and north central North Dakota tonight into Friday morning.

- Windy with increasing chances for rain this weekend.
  Temperatures remain slightly to well above normal through
  Sunday afternoon.

- Much cooler next week, with medium chances for rain around
  mid week.

&&

.DISCUSSION...
Issued at 414 AM CDT Thu Oct 9 2025

A mid level shortwave embedded in southwest flow aloft that is
transitioning to zonal flow is crossing the western Dakotas early
this morning, but the atmosphere remains too dry to even support any
clouds with this wave. A surface trough is analyzed across western
North Dakota and slowly drifting eastward. A pooling of boundary
layer moisture and lighter winds along the interface of the trough
has allowed patchy dense fog to develop. The fog will likely
continue until mid morning and be migratory with the surface trough,
but should remain west of Highway 83.

A potent shortwave over northern Saskatchewan early this morning is
forecast to dive southeastward towards the western Great Lakes this
afternoon through tonight, turning flow aloft to the northwest. The
surface trough will also continue to drift eastward and be followed
by another surface high pressure. Another mild and dry day with a
mostly sunny sky is anticipated, with high temperatures in the mid
60s to mid 70s. Model consensus positions the center of the surface
high squarely over the western half of the state late tonight. The
only possible mitigating factor to a full night of strong
radiational cooling is stronger winds above the surface, but these
winds are forecast to relax over the western third of the state by
the middle of the night. The low temperature forecast for tonight
has therefore been lowered to the 10th percentile of the NBM
distribution, giving mid 20s to lower 30s across most of western
North Dakota. Central North Dakota could see a few pockets of sub-
freezing lows tonight, but should more broadly remain in the mid 30s
to around 40.

The surface high is forecast to drift into the Red River Valley on
Friday while a trailing upper ridge axis shifts into the western
Dakotas. This should promote a cooler day across central and eastern
North Dakota and a comparatively warmer but much breezier day in the
west. Highs on Friday are mainly forecast in the 60s. Southeast
winds could gust as high as 25 to 30 mph along the Montana border
Friday afternoon. On Saturday, a longwave trough is forecast to
deepen over the western CONUS, shunting the north central CONUS
ridge axis to the east. The resulting southwest flow is forecast to
pick up monsoonal moisture and shortwave energy from the remnants of
Tropical Storm Priscilla and bring them into the Northern Plains.
Although both the moisture and forcing will not be nearly as potent
by the time it reaches the Northern Plains, there could still be
some scattered light rain showers and perhaps a rumble of thunder on
Saturday. The time period from Friday night through Saturday night
is also expected to feature a persistent and strong southerly return
flow that could keep overnight temperatures as warm as 50 degrees in
western North Dakota Friday night and central North Dakota Saturday
night. Highs on Saturday could be limited to the 60s across central
North Dakota, where chances for rain are relatively higher, while
far western parts of the state are more likely to reach the 70s. It
will also be windy on Saturday, with southerly winds gusting to 30
to 40 mph.

There is strong model consensus that a potent shortwave will eject
from the base of the western CONUS longwave trough into the Northern
Plains Saturday night into Sunday, inducing surface cyclogenesis
over southeast Montana. The surface low and its parent shortwave are
projected to track northeastward into southwest Manitoba by Sunday
night and occlude by Monday morning. Ensemble cluster analysis
reveals only subtle timing and location differences with the track
of the surface low. Furthermore, there is high confidence in a
strong dynamical system, with ensemble mean MSLP around 992 mb and
medium point-specific probabilities for MSLP less than 990 mb. This
system could be responsible for a variety of notable weather
phenomena over our area from late Saturday night through Sunday
morning. The highest confidence is in a strong wind forecast. The
attendant cold front is forecast to cross the state during the day
Sunday, with deterministic guidance showing strong magnitudes of
cold air advection and pressure rises. Mean mixing potential
initially appears to be around 35-40 kts through Sunday afternoon,
but increases closer to 45-50 kts as the low really begins to wrap
up over southern Manitoba Sunday evening. This would place the
strongest winds over northern parts of the state Sunday evening
through Sunday night. Because this most-likely outcome has just
recently solidified itself, will refrain from making forecast
adjustments to winds for this forecast cycle, although there is a
much higher probability that the current NBM output is too weak.

There are several potential sources of precipitation from this
system. Initially, the lead shortwave that originated from the
remnants of Priscilla could continue to produce scattered showers
Saturday night into Sunday morning, but the eastern half of the
state is more favored to see this activity. Much of the state could
end up in the dry slot during the day Sunday, but depending on
timing, the nearly stacked forcing of the surface cold front and
strong DCVA could ignite a line of showers or thunderstorms during
the afternoon. Ensemble mean CAPE is lower than 500 J/kg, but
conceptually, this seems like the type of system that could produce
stronger warm air and moisture advection than is being modeled. If
so, a low CAPE/high shear severe environment cannot be ruled out.
Last up is the deformation wrap-around precipitation. Latest model
guidance shows this primarily impacting northwest and far north
central North Dakota Sunday evening through early Monday morning.
The concern now with its timing and placement is that it could
become cold enough for precipitation to mix with or change over to
snow Sunday night. The NBM is showing a 20 to 40 percent chance of
measurable snow and a 10 to 20 percent chance for at least an inch
of snow in the northwest, although that doesn`t take into account
initial melting on contact with the ground. This signal also shows
up in cluster analysis, although the GEFS is clearly skewed colder
than the ECMWF ensemble system. If it does end up snowing, there is
then the question of how much the wind would impact conditions with
the falling snow. There are still a lot of forecast details to be
worked out with this system, but it seems to be trending in a more
impactful direction.

It will become much colder behind the front, with Sunday night lows
forecast in the upper 20s to upper 30s and highs on Monday mostly in
the mid 40s to mid 50s. Temperatures similar to these are favored to
continue through at least the middle of next week. A period of drier
weather is in the forecast for early next week until another deep
western CONUS trough sends another shortwave or series thereof into
the Northern Plains by the middle of the week. Cluster analysis
reveals two distinctly different precipitation outcomes for next
Wednesday and Thursday, but it is worth noting that higher
membership clusters are consistently wetter than their lower
membership counterparts.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 414 AM CDT Thu Oct 9 2025

Patchy dense fog will impact parts of western North Dakota
until around 15Z, including at KDIK. VFR conditions are
otherwise expected through the forecast period. Winds will
become northwesterly around 10 kts this afternoon, with some
higher gusts possible across the north.

&&

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

&&

$$

DISCUSSION...Hollan
AVIATION...Hollan