391
FXUS63 KABR 091453
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
853 AM CST Tue Dec 9 2025

.KEY MESSAGES...

- Approaching clipper system will (60-95% chance of occurrence)
  generate a period of light freezing rain today, starting out
  early this morning across north central South Dakota, before
  shifting over into northeast South Dakota and west central
  Minnesota by mid morning through early afternoon. Temperatures
  warm above freezing from west to east throughout the morning
  into early afternoon today. A Winter Weather Advisory remains in
  place this morning for the freezing rain potential.

- Northwest winds this afternoon through tonight are expected to
  gust in excess of 50 to 65 mph across central and north central
  South Dakota. Gusts in excess of 50 mph are also expected over
  northeast South Dakota and west central Minnesota by early this
  evening, persisting into the early morning hours on Wednesday. A
  High Wind Warning is in effect for these dangerously strong
  winds.

- By the end of the week, colder air is expected to move in. High
  temperatures will be in the single digits above 0, with
  overnight lows as low as the teens below zero. Wind chill values
  Friday and Saturday morning could be as low as -20 to -30
  degrees.

- Multiple rounds of snow will be possible late this week.
  Northeastern South Dakota into western Minnesota has a 30-50%
  chance of 2" of snow Thursday through Friday. A band of snow may
  impact the area over the weekend, although there is still a lot
  of uncertainty in the tracks and amounts.

&&

.UPDATE...
Issued at 849 AM CST Tue Dec 9 2025

While DOT 511 site still shows some areas of slippery/icy road
conditions in north central South Dakota, temperatures along the
northern end of the Highway 83 corridor have warmed into the mid
30s, with the SDSU mesonets supporting above freezing temperatures
since about 6 am. As such, have removed the western most counties
from the winter weather advisory.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY AFTERNOON/...
Issued at 357 AM CST Tue Dec 9 2025

At 3 AM CST, there was a pocket of freezing fog in the James River
valley (mainly Brown County), although, Watertown briefly dropped
visibility into some fog as well. It is cloudy over the CWA this
morning, with temperatures west of the James River valley
predominantly in the mid 20s to upper 30s (warmest out along and
west river). Within and east of the James River valley, temperatures
were mainly in the teens to mid 20s. Precipitation is overspreading
the northern high plains of Montana and far western North Dakota,
heading in this direction.

Only adjustments to the Winter Weather Advisory for freezing rain
was to add a couple more tiers of counties for a few hours for the
early part of this morning when WAA-forced precipitation (rain)
reaches north central South Dakota (expected prior to 12Z). The MRMS
Sfc Probability of subfreezing road temperatures over the next 60
minutes supports this brief expansion of the freezing rain headline
over to Corson/Dewey counties from 11Z to 16Z this morning. Did
break off a piece of the pre-existing "northeast SoDak" wint wx
headline area in order to create a "between the MO and James River
valleys" hazard segment to include Campbell, Walworth, Potter and
Faulk counties, running from 12Z to 18Z. Otherwise, the rest of the
Winter Weather Advisory is basically the same, timing/coverage-wise,
and the High Wind Warning remains in place, unchanged from what the
Monday day-shift crafted when they issued the High Wind Warning.

Should be looking at a corridor of time this morning when freezing
rain is happening from west to east across the CWA, predominantly
throughout and north of the U.S. Highway 212 corridor. Strong post-
cold frontal 0.5km mixing winds on a 16+hpa 6-hourly pressure rise
bubble should be able to produce sustained winds at 40 mph for an
hour or more, or gusts well in excess of 60mph sometime between late
this afternoon and late tonight. Regarding post-clipper system
snowfall on the backside of the system late tonight into Wednesday
morning, there is now a small section of terrain-influenced "near
blizzard"-type blowing snow being produced by the blowing snow model
across a portion of Marshall and Roberts counties tonight between
roughly 05Z and 10Z when winds and temperatures and upslope on the
Prairie Coteau may be able to overcome the general lack of any sort
of meaningful snowfall-rates to produce some localized/isolated
rather poor visibility in falling/blowing snow. A new wrinkle for
the next shift to debate.

Despite the warming process coming to an abrupt halt yesterday at
the James River valley (temperatures did warm up quite a bit west of
the James River valley yesterday), still going with a significant
warm-up today, CWA-wide. So, after two days of snowmelt, topped with
several hours of rainfall potential, there should be no blowing snow
concerns across central/north central South Dakota. Once
temperatures fall back below zero this evening, the remaining
modified snowfield should transition into blocks/sheets of ice.
Similar outcome expected across northeast SoDak and west central
Minnesota this afternoon/evening, although CAMS/deterministic GSM`s
do hint at there being some falling snow (generally less than an
inch except up on the far northern portion of the Prairie Coteau)
potential later tonight into Wednesday morning across far northeast
South Dakota and west central Minnesota.

After how warm it will be today, Wednesday will feel like quite a
shock to the system, when high temperatures will only be in the
upper teens to low 30s over the CWA.

&&

.LONG TERM /WEDNESDAY EVENING THROUGH MONDAY/...
Issued at 357 AM CST Tue Dec 9 2025

The pattern of the Northern Plains remaining on the front side of
the upper-level ridge over the western CONUS. With this setup, a
couple of jet streaks will move over the area, providing enough
divergence aloft to support precipitation Thursday through early
Friday. Model soundings indicate that snow is the most likely
precipitation type through the event, but there will be chances for
rain and freezing rain as well. The latter precip types could occur
with a de-saturation of the DGZ aloft during the event, which could
transition from ice formation to liquid formation aloft depending on
how cold temperatures at the top of the saturated layer remain.
Latest ensemble medians have broad coverage of 0.10"-0.20" in liquid
totals through Friday morning, with the highest totals over north
central into northeastern South Dakota. This will translate to
around 1"-2" across much of the forecast area, although varying snow
to liquid ratios (~10:1 over north central South Dakota ranging to
~15:1 over northeastern South Dakota) may create a disparity between
the highest liquid equivalent and highest snowfall locations. Latest
probability of at least two inches peaks over northeastern South
Dakota, ranging from 30 to 50 percent.

With this setup, a strong blast of cold air is expected to move into
the region Friday into Saturday. 850mb temperatures by Saturday
morning are expected to be in the teens below 0 Celsius, which is
below the 10th percentile for this time of year. The presence of
this cold air will lead to overnight lows at the surface below zero
Fahrenheit Friday and Saturday mornings. At these temperatures, wind
chills are expected to reach -20 degrees Fahrenheit in most of north
central and northeastern South Dakota, and potentially even approach
the Cold Weather Advisory Criteria of the northern counties of -30
degrees Fahrenheit. Friday morning is of particular concern, because
while temperatures are slightly warmer than Saturday morning,
northwesterly winds of 20-25 miles per hour gusting to 35 overnight
will counteract that difference. The latest long-range ensemble
guidance put the probability of hitting -30 degrees Fahrenheit for
the minimum overnight wind chill in northeastern South Dakota at 20-
40% on Friday morning, easing up to around 10-20% Saturday morning.

Yet another round of snow may impact the region this weekend, this
time being more banded with a swath of heavier precipitation totals.
There is still a lot of uncertainty remaining, but it is worth
noting that forecast snow totals have jumped up over the latest
forecast cycle. The latest NBM currently puts a band of 50%
probability to see 2" of snowfall accumulations, with a band of 20-
30% chance for up to 4".

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 531 AM CST Tue Dec 9 2025

Terminals KABR,KATY,KPIR,KMBG

Still dealing with a couple of pockets of fog/low clouds at
KABR/KATY this morning. IFR fog/stratus should abate by 15Z, just
in time to grapple with VFR/MVFR conditions in freezing rain.
Temperatures should warm up enough for plain rain to take over at
KABR/KATY by early afternoon, just in time to grapple with very
strong northwest winds developing. Sustained winds over 30 knots,
with gusts over 45 knots are expected. Low level wind shear
potential will exist for much of the afternoon into this evening,
as well.

VFR conditions, to start, at KPIR/KMBG could have brush with MVFR
visibility in rain (at KPIR) or freezing rain (at KMBG) this
morning. Otherwise, VFR condition are expected at KPIR/KMBG from
about 18Z to the end of the TAF valid period. Very strong
northwest winds are expected at KPIR/KMBG, as well, by early this
afternoon, with sustained winds over 35 knots and gusts over 50
knots. Low level wind shear potential will exist for much of the
afternoon into tonight, as well.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...High Wind Warning from 3 PM this afternoon to 6 AM CST Wednesday
     for SDZ006>008-011-018.

     High Wind Warning from 11 AM this morning to 2 AM MST Wednesday
     for SDZ003-015.

     High Wind Warning from 3 PM CST /2 PM MST/ this afternoon to 3
     AM CST /2 AM MST/ Wednesday for SDZ004-005-009-010-016-017-
     033>037-045-048-051.

     Winter Weather Advisory until noon CST today for SDZ005>008-010-
     011-017>023.

     High Wind Warning from 6 PM this evening to 6 AM CST Wednesday
     for SDZ019>023.

MN...Winter Weather Advisory until 3 PM CST this afternoon for MNZ039-
     046.

     High Wind Warning from 3 PM this afternoon to 6 AM CST Wednesday
     for MNZ039-046.

&&

$$

UPDATE...07
SHORT TERM...10
LONG TERM...BC
AVIATION...10