470
FXUS63 KABR 111129 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
529 AM CST Thu Dec 11 2025

.KEY MESSAGES...

- Wintry mix of snow, sleet, and freezing rain expected across
  portions of mainly central and north central South Dakota, with
  mainly snow and some sleet expected across portions of northeast
  South Dakota now through late this afternoon. Ice accumulation
  of a few hundredths to a couple tenths of an inch expected
  across central/north central South Dakota. Snow accumulation
  will generally be around 1 to 3 inches across northeast South
  Dakota.

- Another band of snow is expected to move into the area Saturday.
  There is still a lot of uncertainty in the storm track and
  amounts, but there is a 30 to 50% chance for central South
  Dakota to see upwards of 2" of snowfall accumulation.

- A blast of very cold air is expected to bring temperatures 20-30
  degrees below normal Saturday into Sunday. Highs will be in the
  positive single digits Saturday, while overnight lows Saturday
  into Sunday could get as low as -20 degrees. Wind chills of -30
  degrees or lower will be possible early Sunday morning.

&&

.UPDATE...
Issued at 523 AM CST Thu Dec 11 2025

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/...
Issued at 310 AM CST Thu Dec 11 2025

At 3 AM CST, a few pockets of light snow were trying to happen
between the James and Missouri River valleys. The main takeaway this
morning, though, is the increasing/widespread coverage of freezing
rain developing across western into central South Dakota beneath a
large 150-170knot upper level speed max enhancing mid-level
WAA/frontogenesis over the region. Temperatures throughout the CWA
range from the single digits above zero over west central Minnesota
to the low/mid 20s west river. Winds were southeast around 5 to 15
mph.

No changes planned to the headlines. There continues to be some
shifting/changes in placement/amounts of freezing rain/sleet/snow
and their corresponding ice and snow accumulation footprints.

Ensembles/deterministic GSMs/CAMs still generating a stripe of
freezing rain ice accumulation in the 0.10 to 0.20 inch range, but
have shifted things west, now centered along a line from near
McLaughlin to Onida to Wessington area. Snow amounts have come up
some (0.5 to 1.5 inches) across northeast South Dakota and a little
bit further west in the CWA compared to 24 hours ago. Instead of
canceling counties along the eastern edge of current advisory
coverage, will leave in place for now, in case the next couple of
iterations of guidance should "pendulum swing" snow/ice accum
footprints back to the east. Should be seeing decreasing uncertainty
as the event is beginning to unfold, but instead, models/guidance
are still shifting things around.

By 00Z this evening, today`s snow/sleet/freezing rain event should
be diminishing to scattered flurries/very light snow for several
hours into the tonight period across north central and northeast
South Dakota (minimal snow accum potential currently expected with
any lingering overnight snow). On the heels of this event, low level
CAA will commence, along with moderate pressure rises as surface
high pressure begins to build into the region. As winds pick up to
15 to 25 mph with gusts to 35 mph ("breezy") out of the northwest,
the blowing snow model is generating drifting to isolated blowing
snow conditions sporadically across the CWA from west to east. Looks
sub-advisory at this time, but will continue to monitor. Friday
looks mostly dry and cold with surface high pressure shifting east
in the region, as the next clipper low begins to work into the
region from the west.

&&

.LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/...
Issued at 310 AM CST Thu Dec 11 2025

As the long term period begins Friday night into early Saturday
morning, another band of precipitation will be moving into the
forecast area supported by a jet streak aloft. Timing wise,
precipitation will begin late Friday night and be out of the area by
Saturday afternoon. The heaviest precipitation is expected between
00Z and 06Z Saturday morning.

There is still quite a bit of uncertainty with the amounts and the
track of this system, as both have changed significantly from the
previous forecast cycle. In terms of forecast track, model guidance
have continued to shift the axis of heaviest precipitation southwest
over the past few cycles. The highest precipitation totals now sit
over central South Dakota, but if this trend continues it is
possible that the precip could shift out of the forecast area
entirely. Snow is the expected precipitation type through the event,
and the totals have increased over the past forecast cycle. 50th
percentile values in the NBM have jumped up from around 2" at the
most in the forecasts from 12 and 24 hours ago to 3-4" with the
latest run. This increase in snow totals makes sense when looking at
model soundings, which indicate that a deep, saturated DGZ extending
from near the surface to ~600mb will exist. This will support the
production of light, fluffy snow, with ratios up to 20:1 or greater
possible. Looking at NBM`s current 90th percentile as a "worst case
scenario" shows about 6" of accumulation in central South Dakota,
mainly in the Pierre area. With the continuing shift in the storm
track and the uncertainty in amounts, no headlines will be issued at
this time. However, should the track settle in and snowfall amounts
either remain the same or increase further, a headline would
definitely be warranted over central South Dakota.

A shot of extremely cold air is expected this weekend, with 850mb
temperatures dropping to -20 degrees Celsius in parts of
northeastern South Dakota. This will push surface temperatures 20 to
30 degrees Fahrenheit below mid-December normals Saturday afternoon
into Sunday morning. Highs Saturday will struggle to get above 0
degrees, particularly in northeastern South Dakota. Overnight lows
will approach -20 degrees Fahrenheit, and a record low at Sisseton
is very achievable (the current daily record low for December 14th
being -20, set in 1989). With air temperatures so low, it won`t take
much to drop wind chills to be dangerously low. The latest long-
range ensembles put the probability of needing a Cold Weather
Advisory (-30 degrees wind chills) at 30-50 percent over
northeastern South Dakota into western Minnesota. The highest
chances are highlighted in the James River Valley.

Next week, the upper-level ridge that has been in place will finally
begin to transition east and flatten out, ending the parade of
clipper systems the region has been under recently. Chances for
additional precipitation appear low at this time. With this return
to mainly zonal flow aloft, temperatures will warm up to become
normal to above normal by mid-week (highs into the 30s and 40s). The
entirety of the forecast area is currently expected to see above
freezing temperatures by Tuesday, meaning that the existing snowpack
will be able to melt.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 523 AM CST Thu Dec 11 2025

Terminals KABR,KATY,KPIR,KMBG

CIGs are expected to lower to MVFR/IFR through the TAF period
along with the arrival of fzra/SN at KPIR/KMBG/KABR, with VSBY
down to MVFR/IFR in heavier precipitation. SN should be reaching
KATY prior to 18Z today. Confidence on timing of precipitation
and changeover times remains not very high, but best estimates
are in the TAFs. Later tonight (after 00Z), northwest winds should
pick up to 10 to 20 knots with gusts at or above 30 knots. This
may cause some minor drifting/blowing snow overnight, mainly at
KABR/KATY.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Ice Storm Warning until 5 PM MST this afternoon for SDZ003.

     Winter Weather Advisory until 6 PM CST this evening for
     SDZ004>006-009-010-016>018-034>037-051.

     Winter Weather Advisory until 6 PM CST this evening for SDZ011-
     019>023.

     Winter Weather Advisory until 3 PM CST /2 PM MST/ this afternoon
     for SDZ015-033-045-048.

MN...None.
&&

$$

UPDATE...10
SHORT TERM...10
LONG TERM...BC
AVIATION...10