344
FXUS63 KABR 181752
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1252 PM CDT Sun Oct 18 2026

.KEY MESSAGES...

- Patchy to areas of frost is possible across portions of north
central and northeastern SD early Monday morning. No freeze is
anticipated.

- Slightly warmer than normal temperatures stick around through the
midweek with the potential for temperatures to be 15 to 20 degrees
above normal by the end of the week.

- Dry conditions continue through Thursday with rain chances (30-
50%) potentially returning Friday evening into Saturday. Low
confidence in exact track and timing of the system along with
estimated rainfall amounts at this time.

&&

.DISCUSSION...
Issued at 1252 PM CDT Sun Oct 18 2026

The cold front is currently extending over west central MN and
southwestward though west central NE connected to a 982mb low over
northeastern Manitoba/Hudson Bay. With the exception of
east/southeast SD still ahead of the front, the rest of the CWA is
in north to northeast flow with some gusty winds (20-35 mph)
tracking right behind it, per weak CAA, over central SD to the James
River. Downsloping winds off the Coteau will continue to diminish
and finally end once the wind shifts to the northeast.

The ~1023mb high pressure will continue to slide in from the
northwest, with the center over ND/MT/Canada border by 06Z. This
high will remain dominant over the region Monday as we continue with
dry conditions. Per this high and ongoing weak CAA, temps will be a
few degrees cooler at any one location overnight than what we saw
earlier this morning and around the same over the Coteau per
inversion. Overall low temps are forecast to range in the upper 30s
to the lower 40s. Probability of temperatures below 36 degrees (for
frost formation) is 40-65% but spotty over north central and
portions of northeastern SD (mainly along the ND/SD border and James
Valley) per REFS/NBM. Probability of temps at 35 decrease a bit (20-
40%) for these areas with a 0% chance of temps dipping at 32 or
lower. So patchy to areas of frost are in the grids for these areas
with no freeze expected at this time. Highs for Monday will be the
"coolest" of the week with temps ranging in the lower to mid 60s.
This high will track east Monday with the CWA between this high and
broad area of low pressure to our west Tuesday with ongoing dry
conditions. Lack of any moisture in this dry air mass keeps the
forecast dry through Thursday.

Looking at the pattern aloft by midweek, it will consist of
southwest flow over the region as Clusters overall agree on a closed
cutoff low developing over the Pacific and nearing the CA coast by
Wednesday morning with a weaker open wave developing over the Gulf
of Alaska. Due to this a broad ridge will build east of the Rockies,
and really amplifying over the region Thursday, shifting eastward on
Friday. Winds will be south/southeasterly at the surface and
southwest at 850mb ahead of the low within the warm sector these
days. This will also lead to a bit more moisture to return at lower
levels as dewpoints are forecast to increase back into the 50s.
Highs are forecast in the 70s, however, the 25-75th spread is 5-7
degrees as we are several days out. Clusters indicate this southern
cutoff low becomes an open wave as it tracks over the western CONUS
Thursday with a bit of a difference in ensembles on whether these 2
waves phase together or remain separate in split flow as the overall
trough tracks east/northeast into the central and northern CONUS.
With its developing surface low over the Northern Rockies Friday,
models indicate the return of precip (30-50% NBM) Friday into
Saturday as the low/cold front is forecast to strengthen as it
tracks northeast in Canada Saturday. Models seem to have a good
handle of this setup but exact placement and intensity of the
surface low (and wave aloft) does vary a bit as GEFS indicates a
stronger wave/sfc low with GEPS a bit weaker and ENS right in
between. This results in low confidence of precip timing and QPF
amounts which is why NBM pops are broadbrushed. Looking at the
probability of or exceeding 0.25" per mean ensemble (GEFS/ENS/GEPS)
is only about 25-35%. Again this is several day out, so
probabilities for precip and QPF amounts will change.

With this incoming system/steeper pressure gradients ahead of the
low will lead to winds increasing along and west River Thursday
afternoon, with gusts up to 35 mph. Widespread stronger winds are
forecast Friday as this low deepens with gusts potentially ranging
from 35 to 45 mph Friday afternoon across the CWA with a prob of
over 45 mph per NBM is 35-45% here and there for now. Relative
humidity at this point looks to stay above 40% but with the lack of
rain/dry air we have been dealing with and the warmup expected for
the end of the week, the Grassland Fire Danger Index jumps into the
High Category along and west River Thursday and High Category pretty
much over the entire CWA Friday. This is still a few days away and
mentioned above, depends on strength of low/pressure gradients which
results in what the gusts will be, but this is something to watch
for any elevated fire danger concerns.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1218 PM CDT Sun Oct 18 2026

Terminals KABR,KATY,KPIR,KMBG

VFR cigs prevail through the TAF period with passing high
cirrus clouds at most. The cold front currently extends from
west central MN and southwestward through north central NE. With
the exception of KATY still in southwest flow, the rest of the
TAF sites are behind the fropa with north to northeast winds.
Weak CAA behind the front is leading to breezy winds with gusts
of 20-35 mph across central SD. As the front tracks further
away from the CWA winds will diminish this evening as a high
moves in over the region. Light winds will continue out of
northeast overnight, switching to more of a easterly direction
through Monday morning west to east across the region.

&&

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

&&

$$

DISCUSSION...MMM
AVIATION...MMM