358
FXUS63 KABR 232031
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
231 PM CST Sun Nov 23 2025

.KEY MESSAGES...

- Winter conditions arrive on Tuesday, with strong northwesterly
winds and snow for many locations. Below normal temperatures are
also expected through the beginning of December, with below zero
wind chills possible over northern South Dakota.

- Rain on Monday night (70% chance) over northern South Dakota will
transition to snow on Tuesday morning. The snow will fall light to
moderately at times over northeast South Dakota and west-central
Minnesota on Tuesday afternoon. There is a 30 to 60 percent chance
for greater than an inch of snow over northeastern South Dakota
Tuesday through Tuesday night, with the highest amounts expected
over Marshall County. Patchy blowing snow will be possible Tuesday
into Tuesday evening over north central to northeastern South Dakota.

- Northwest winds will increase Tuesday morning, with gusts of 35 to
50 mph Tuesday afternoon. The strongest winds will be over south
central South Dakota, where gusts may occasionally reach 60 mph.
This will also lead to high to potentially very high Grassland Fire
Danger Index values over portions of central South Dakota on Tuesday.

&&

.SHORT TERM /THIS EVENING THROUGH MONDAY AFTERNOON/...
Issued at 220 PM CST Sun Nov 23 2025

The main highlight in the short term will be a storm system tracking
across the region early next week. Patchy to areas of fog is also
possible once again late tonight into Monday morning, mainly for
locations along the James River and over the Coteau.

By 00Z Monday, models agree on split flow aloft with a broad low
amplitude ridge stretching across the northern half of the CONUS
with an embedded shortwave, and its weak surface low, over southern
Manitoba. The southern stream consists of a nearly stacked 500mb
closed low to surface over Colorado. Through 12Z Monday, the
~1009mb Colorado low will track into western Kansas with models
overall agreeing on this location, with GEFS just a touch
northwest than the other models. Through the afternoon, this
Colorado Low will then track southeast (as its closed low turns
back into an open wave) with models overall agreeing on the center
of the low along the KS/OK border by 18Z (and its now open
shortwave trailing shortly behind). At the same time, a shortwave
will move in off the Pacific and over the Pacific Northwest with
its broad area of low pressure setting up over northeastern WY and
northwestward into MT. Luckily any precip with this CO Low will
remain south of our CWA. With a fropa dipping southward over the
CWA Monday (from this low in Canada) winds behind it will switch
out of the north/northeast.

&&

.LONG TERM /MONDAY EVENING THROUGH SUNDAY/...
Issued at 220 PM CST Sun Nov 23 2025

Primary focus of the long term part of the forecast will be the
transition from Fall to Winter on Tuesday, which will remain through
the start of December. The transition will be driven by a strong
shortwave over the Pacific that will move into the PacNW tonight and
then quickly move east into the northern Plains Monday night and
depart Tuesday evening. Expect this shortwave and associated weak
surface low (around 1009mb) to bring an initial push of light rain
to northern SD on Monday night. Then as the low moves east Tuesday
and intensifies over eastern MN and western WI during the afternoon,
it will wrap in much colder air on Tuesday morning, switching the
rain to snow from northwest to southeast and eventually putting the
northeast half of SD and west-central MN in wrap around snow into
the evening. The combination of the snow, with strong N-NWrly winds,
will lead to travel impacts for northeast SD and west central MN on
Tuesday.

First for the winds. The initial surge of cold air advection behind
the front will lead to the strongest winds over central and
especially south central SD on Tuesday, where 0.5km winds are in the
35-45kt range. Thus, expect gusts easily in the advisory range for
areas along and especially west of the Missouri River on Tuesday.
Wouldn`t be surprised to see some High Wind Warning gusts for
Jones/Lyman counties, which is supported by the NBM 24hr wind gust
probabilities of 55mph or greater being over 70%. Farther east to
the James River Valley, think that area should see some gusts to
advisory level (NBM has 24hr probs on Tuesday around 70%) and they
too may eventually need an advisory. That matches up with the EC-EFI
data highlighting much of SD, except the northeast, with 0.7-0.8
values, which traditionally lines up with advisory winds for our
area. Will need to watch the tightening pressure gradient Tuesday
aftn/evening near the MN/ND/SD border areas, as the surface low
strengthens. This could lead to an enhanced 6hr period of winds with
gusts reaching advisory level.

The strong winds and dry fuels will lead to elevated fire weather
concerns for locations that don`t experience precipitation on
Tuesday. That looks to primarily be in south central SD, so despite
RH values being up towards 60%, the strength of the winds may
support the need for a Red Flag Watch/Warning.

Finally, some additional details on the snow side of the forecast. As
mentioned previously, expect to see a steady transition from rain to
snow from northwest to southeast on Tuesday morning, as the cold air
surges into the area. With that transition, do expect snow
accumulations and winter impacts to increase as we go through the
day on Tuesday. EC-EFI Snow highlights ND as having the best chance
for more significant accumulations compared to model reforecasts,
with some higher EFI values (and shift of tails - indicating a few
models having some higher end snowfall amounts) over the northern
portions of the Prairie Coteau. For example, GEFS has a few members
up over 10" for Sisseton (and EC-Ens has 5 over 8") with a 10-1 SLR,
thus the shift of tails over 0 and towards 1. But when looking at
the plumes at this point, the thing that stands out is the large and
evenly distributed spread in the members (between nothing and the
previously mentioned high end amounts), thus leading to a higher
than normal uncertainty on amounts for Tuesday into Tuesday evening.
That makes sense with the northeastern part of SD currently being on
the southern edge of the heaviest snow. Thus, any shift north/south
of the track of that snow swath will greatly impact snowfall
amounts. In the end, the current 25th-75th percentile snowfall
amounts from the NBM for Sisseton are in the 1-6" range (and Trace
to 2" along a line from Eureka to Aberdeen to Watertown), so stay
tuned as we continue to refine the forecast over the next 24hrs.
Finally, with the expected winds and falling snow, do expect reduced
visibilities where they overlap and if we do see increasing snow
accumulation in the northern portions of the Prairie Coteau, could
see at least some isolated locations of visibitilies below 0.5 mi.

For the rest of the week...

A high moves in on Wednesday and remains into Thursday. Could be
some light precip moving into western SD later Thursday and sliding
southeast with time into Friday, associated with an shortwave
dropping southeast through the northwest flow aloft (and mid level
WAA). Still some uncertainty in the ensembles on the location and
amounts, but in general, seems like snow accumulations will be light
(NBM 24hr probs of 1 inch or greater is 50-70%). Beyond that,
uncertainty remains into the weekend, as an upper trough deepens
over the southwest CONUS this weekend and remains in the first part
of next week. Ensembles are consistent on the upper trough being
present, but differ on the location of the trough axis and how
amplified it will be. That being said, with the baroclinic zone
setup to the southwest of our area, stretching from western MT
through southwest SD and into central NE, we`ll still have the
potential for periods of light snow this weekend (30% chance). In
addition, high temperatures will be 10-15 degrees below normal and
in the 20s.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1132 AM CST Sun Nov 23 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast to prevail through the TAF period with
light winds. However, patchy to areas of fog may develop over
portions of the region late tonight through early Monday morning
which would bring a drop in visibility at times. Low confidence
in exact coverage at this time, but may affect the TAF sites.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

SHORT TERM...MMM
LONG TERM...SRF
AVIATION...MMM