518
FXUS63 KABR 091114
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
614 AM CDT Thu Oct 9 2025

.KEY MESSAGES...

- Strong south winds during the morning hours will top out between
25 and 35 mph with some local gusts over 40 mph in the favored
downslope areas. Winds will slowly diminish through the afternoon.

- Light rain this weekend, mainly for the James River Valley and
eastward. Probability of rainfall of a quarter of an inch or more
ranges from 30 to 60 percent for this area, highest along and east
of the Sisseton Hills.

- Winds will increase out of the southeast Saturday with gusts of 30
to 40 mph through Sunday before diminishing Sunday night.

&&

.SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/...
Issued at 217 AM CDT Thu Oct 9 2025

This morning there are steady winds (20-30+ mph) across much of the
forecast area with a tight surface pressure gradient on the west
side of a broad high pressure system. In that southerly flow there
is also a shallow stratus layer up around 6kft over the eastern CWA.
All of this migrates east through the course of the day, so while we
do have a core of low level winds up around 40kts in the east by
daybreak, that mixes out and shifts east with slackening winds
through the afternoon with the passage of a weak front. Another
broad high pressure system noses into the north central part of the
state tonight, and sits overhead for Friday.

Favorable mixing as winds shift with the trough, and mild
temperatures aloft, with the clouds mainly in the far east, should
be easy to make NBM temperatures in the low to mid 70s. The core of
higher humidity is also still in place with low to mid 50 dewpoints
but will also shift out of the area with the front.

&&

.LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/...
Issued at 217 AM CDT Thu Oct 9 2025

Quite an interesting setup aloft this weekend into early next week.
The best way to put it is that we have a split flow troughing
pattern over the western CONUS and western Canada with a ridge over
the region Friday evening. The axis of a shortwave trough, in this
overall longwave trough pattern over the western CONUS, tracks
northeastward and over the Northern Plains through the weekend as it
tracks into Canada. The northern wave over western Canada tracks a
bit southeast and gets entangled with the southern wave (Fujiwara
effect!), where a closed low forms over the Pacific Northwest ~early
Monday morning. This low then slowly tracks south becoming an open
wave by the middle/end of next week. Clusters overall agree on this -
PNA pattern but do differ on the exact intensity/position of this
trough towards the end of the long term period.

At the surface Friday evening through Saturday morning, a high
pressure system will be working its way eastward (and ridge aloft)
and exiting the region with the center of the Canadian low over
~Alberta by 12Z Saturday. The low will track east then northeastward
across Canada as it occludes. Another low pressure system forms over
~MT Saturday (and deepens) as it tracks east then northeastward
(over the Northern Plains) into Canada through Sunday evening, where
it is forecasted to occlude as well. Ensembles agree pretty well
with the position and track of the low. With this setup, a couple of
rounds of precip is possible over the CWA. The first round will be
light as NBM pops only have a 15-25% Saturday through Saturday
evening associated with the warm front. As this broad low is then
positioned over western Dakotas early Sunday, ensembles are in
better agreement, with NBM pops increasing to 40-65% (excluding
south central SD) through the day as the low crosses over the
region, with the highest pops east of the James River. Pops decrease
southwest to northeast over the CWA Sunday evening as the low tracks
out of the region. Probability of rainfall>0.25" is 30-55%, highest
Coteau and eastward. Light pops do return to the forecast area Tues-
Thurs (20-30%) as another system could affect the area, however,
confidence is low on exact timing and setup this far out.

With steepening pressure gradients ahead of the incoming low,
southerly winds will increase aloft with 850mb winds by Saturday
afternoon ranging from 30-45kts and 700 mb winds 20-30kts. Mixing
heights, per GFS soundings, are forecasted around ~2-3K feet with
momentum transfer at the top of the mixed layer ranging from 25-
35kts, highest over central SD. This will lead to winds at the
surface to increase, with gusts of 30-40 mph, highest over central
SD by Saturday afternoon. Winds will remain breezy Saturday night,
per LLJ/mixing and ongoing steeper pressure gradients, with gusts of
25-35 mph, highest over and along the Coteau. Winds will continue to
be gusty Sunday, with gusts up to 35 mph and more widespread over
the CWA. Highs will range in the 60s on Saturday and 70s to near 80
on Sunday. However, the NBM 25-75th spread is quite large (7 to 12
degree). It does cool down early next week with the incoming high
pressure system, with forecasted highs only in the mid 50s to the
lower 60s Monday and Tuesday and lows in the 30s and 40s.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 613 AM CDT Thu Oct 9 2025

Terminals KABR,KATY,KPIR,KMBG

Will start TAFS with strong south winds and LLWS but through the
day those winds decrease in intensity, with a shift to westerly
this afternoon/evening. Otherwise VFR with a 1-2kft thick deck at
6kft near KATY.

&&

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

$$

SHORT TERM...07
LONG TERM...MMM
AVIATION...07