951
FXUS63 KABR 072048
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
248 PM CST Sun Dec 7 2025

.KEY MESSAGES...

- Light snow moves from the James valley to the Sisseton Hills
region this afternoon/evening. Inch or less type snowfalls today.

- Potential for Sisseton hills downslope winds (30 to 40 mph) with
blowing snow issues Monday afternoon.

- Next clipper will most likely (60-80% chance of occurrence) be
preceded by a brief period of light freezing rain Tuesday morning
before temperatures thaw Tuesday afternoon across northeast
SD/western MN.

- Northwest winds Tuesday afternoon and evening could gust in excess
of 50 to 60 mph across central and north central South Dakota. 45 to
55 mph gusts for the northeast Tuesday evening/overnight.

- Some of the coldest air of this winter season could be settling
over the area by the end of the week, including high temperatures
around or slightly above 0F and low temperatures down into the
single digits below to teens below zero and wind chill values Friday
morning as low as -20F to -35F.

&&

.DISCUSSION...
Issued at 247 PM CST Sun Dec 7 2025

North to south band of snow continues to migrate east and is just
now into Aberdeen. Some light snow continues within the stratus to
the west below the radar beam as well. Accumulations on webcams
appear to be light, and there has also been some blowing/drifting
noted with winds west of here in the 15 to 25 mph range. Still
sticking with the "around an inch" messaging with this feature.

As we go through Monday, southerly flow develops out ahead of a weak
surface low that moves through North Dakota. A weak gradient for us
will limit the ability to mix out the coldest air in the northeast
until late, when the low moves into the Red River valley. It should
be noted that while flow is mostly unidirectional aloft, there is a
weak signal for Sisseton hills downslope winds across the northeast
in the afternoon. Despite warming temperatures, there is quite a bit
of blowable light/fresh snow up in the northeast, so bumped up the
wording for blowing snow in the downslope area as BUFKIT shows about
35kts in the critical layer.

The weak clipper moves on, with a weak ridge in place Monday
night/Tuesday morning ahead of a stronger clipper system building in
Alberta/Saskatchewan.  Between  12Z and 00Z it will have zipped from
Canada into the far northeast of South Dakota with a surface
pressure of between 992 and 985mb. Each deterministic model has come
up with a slight variation with this central pressure over the last
few runs, and also with slight variations in placement/track. This
plays into confidence in regards to wrap around precipitation (that
we will address later).

Firstly, out ahead of this system there is already warm air in
place, having previously arrived with the first system and left over
from Monday.  21Z Tuesday, 850mb temperatures are mostly in positive
territory, though models vary on the strength of the warm air.
Generally speaking, its about a standard deviation above climo.
BUFKIT profiles suggest there may be enough of a shallow cold layer
below the warm nose to present a freezing rain threat with any
moisture across the northeast. How much rainfall? NBM 25th/75th
range is a tenth to a quarter inch, with a mean of about a tenth or
two meaning a large range for just a light amount of moisture.
Almost 20 percent of ensemble members fail to generate QPF for
Sisseton for that matter. And with warm advection and a shift to
westerly flow enhancing mixing, temperatures will continue warm as
perception is ongoing. Thus, while freezing rain is a real threat,
the duration is limited to mainly during the onset of rainfall with
a thaw through the day.

Moisture falling on snowpack and the warming temperatures (on top of
what may have been experienced Monday) will severely limit the
blowability of any snow on the ground moving forward.

With the onset of cold advection, winds will see a substantial
upward trend. A 20 to 24mb gradient, with pressure rises of upwards
of 16mb/6 hours will likewise enhance winds. GEFS 850mb winds are 3
standard deviations above climo, and EC EFI/shift of tails continues
to highlight South Dakota for potential high winds. As such, issued
a high wind watch for most likely areas impacted by high winds. East
of this headline, additional headlines will need to be evaluated.
Will it require a wind headline or some sort of winter weather
related headline with wrap around moisture possibly moving into the
CWA? BUFKIT profiles aren`t overly supportive for snow (lack of ice
in the dendritic growth zone) in the wrap around Tuesday night.
Deterministic NBM is only a few hundredths of QPF. There is still
time between now and when this system gets going so any slight
southward shift in the track would result in high potential for snow
falling in a core of 40 to 50 mph winds across the northeast.

That cold air that follows for late in the work week. 850mb
temperatures are a standard deviation below climo. While much of the
snowpack will have been modified at this point, there may be another
round of light snow on Thursday/Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1130 AM CST Sun Dec 7 2025

Terminals KABR,KATY,KPIR,KMBG

An area of MVFR CIGS/VISBY in snow is headed away from the
KPIR/KMBG terminals towards KABR/KATY later this
afternoon/evening. CIGS not expected to improve much though VISBY
will once the snow moves out.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...High Wind Watch from Tuesday afternoon through late Tuesday
     night for SDZ003>005-009-010-015>017-033>037-045-048-051.

MN...None.
&&

$$

DISCUSSION...07
AVIATION...07