626
FXUS63 KABR 311944
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
244 PM CDT Tue Mar 31 2026

.KEY MESSAGES...

- The first of two upcoming winter systems moves into the forecast
area late tonight into early Wednesday morning. Around 4"-7" is
expected over north central and parts of northeastern South Dakota
as well as western Minnesota. Between 2"-5" is expected for central
and parts of northeastern South Dakota. A Winter Weather Advisory is
in effect for all counties (except Jones, Lyman, and Buffalo) early
Wednesday morning through Thursday.

- The Wednesday and Thursday system will also bring chances for
freezing rain to parts of eastern South Dakota, particularly in the
Watertown area. While confidence is low, some parts of Deuel and
Hamlin counties may see upwards of a tenth of an inch of ice through
Thursday.

- Strong easterly winds will gust up to 25 to 35 miles per hour
Wednesday, decreasing Thursday to gust up to 20 to 30 miles per
hour. The combination of falling snow and strong winds will cause
decreased visibility, at times as low as half a mile on Wednesday
in particular.

- A second system will move in from the west Thursday night through
Saturday bringing potential for freezing rain and additional snow.
Impacts to travel are expected. There is a 40 to 70% chance of more
than 4 inches of snow northwest of a line from Murdo to Watertown to
Ortonville. Freezing rain will be possible Thursday night into
Friday morning from Pierre to Watertown.

&&

.SHORT TERM /THIS EVENING THROUGH THURSDAY AFTERNOON/...
Issued at 243 PM CDT Tue Mar 31 2026

The first of two systems bringing winter precipitation arrives
tonight, beginning over central South Dakota. Surface and low-level
temperatures are going to play a key role in determining the
precipitation type during this event, but expecting mainly snow out
of this system overall. There are a couple possible exceptions to
snow as the precipitation type during this event. The first comes on
the front end, where temperatures at the lowest levels may stay
above freezing for the first couple of hours and produce rain over
parts of central South Dakota. However, the freezing level is
expected to be quite low, and the melting layer may not be deep
enough to fully melt the snow before it reaches the surface. This
same concept also applies to Wednesday afternoon should high
temperatures reach above freezing. This may be a challenge however
given the cloud cover present through the day limiting insolation.
The second exception comes over parts of northeastern South Dakota
(the Watertown area in particular) on Thursday morning. Model
soundings indicate a warm nose aloft, and the major question will be
whether or not that warm nose will reach above freezing and melt the
snow falling through the profile. European ensemble runs trend that
warm nose a bit warmer, which is why we see some higher freezing
rain accumulation out of it. The GEFS on the other hand trends it a
bit colder, but is still hovering right around freezing. All this to
say that a subtle warmup in the ~700-800mb layer could be enough for
precip type to switch on a dime in future runs. The latest trends
indicate the the European model is closer to the right track over
parts of eastern South Dakota, and that Deuel and Hamlin counties in
particular may see up to two tenths of accumulation in total through
Thursday.

In terms of snowfall totals through this first event, the last few
NBM runs have consistently shown an upward trend in the median
snowfall amounts, as well as a slight shift north with the latest
run. The track in particular will be something to watch as the event
begins, as there is still some signal for a shift back to the south.
Through Thursday, much of the area is expecting between 3"-7" in
total, and the latest NBM probabilities of 6" have trended up to 50-
75% over parts of north central and northeastern South Dakota as
well as western Minnesota. However, the thought is that these higher
end values are less likely to materialize on the ground for a couple
of reasons. First, given the past few days having above normal
temperatures, most of the ground will be thawed, with current 4"
soil temperatures reading above 40 degrees at nearly all locations.
Therefore, for at least the onset of the event, there may be some
help from the warm ground in preventing snow from sticking until it
cools further. Secondly, given the duration of the event, the
expectation is that there will be plenty of time for compaction to
limit the accumulations. So while upwards of 6" may fall to the
ground, confidence is low on actually seeing 6" of accumulation and
the associated impacts.

A tightening pressure gradient will bring another element into the
equation with this system. Winds out of the east at 20-25 miles per
hour will gust up to 25-35 miles per hour, which when combined with
the falling snow may reduce visibility at times. Snow ratios are
generally expected to be around 10:1 through the event, so being a
bit on the wetter side the snow will likely be more difficult to
blow around from the surface. In addition, snowfall rates will
rarely (if ever) exceed half an inch per hour over the duration of
this event. Therefore, not anticipating blizzard conditions at this
time, although a close eye will need to be kept on visibility
observations through the event. The easterly wind direction will
also create favorable conditions for some potential upsloping along
the Prairie Coteau. This may lead to some localized higher snowfall
amounts may be possible over that area.

As a result of all of these factors, a Winter Weather Advisory has
been issued for all counties, with the exceptions of Jones, Lyman,
and Buffalo. Timing on this Advisory essentially lines up with the
onset and departure of the snowfall. Areas west of Brown and Spink
counties have the Advisory run from 1 AM CDT Wednesday through 1 PM
CDT Thursday. Areas from Brown and Spink counties and eastward are
six hours delayed, beginning at 7 AM CDT Wednesday and continuing
through 7 PM CDT Thursday. An upgrade to a Winter Storm Warning is
not out of the question alongside later forecast packages, but there
are currently no plans to do so at this time.

&&

.LONG TERM /THURSDAY EVENING THROUGH TUESDAY/...
Issued at 243 PM CDT Tue Mar 31 2026

Primary focus for the long term part of the forecast is the second
wave of wintry precipitation for Thursday night into Saturday.

This second wave of precipitation is tied to another upper trough
dropping through the western CONUS, phasing with the southern stream
jet and developing a low in the lee of the Colorado Rockies on
Thursday evening. That low will then track through the KS/MO/NE/IA
intersection region Friday afternoon before lifting northeast
towards WI by Saturday morning. Will note that the AIFS-Ens MSLP
lows does have the track a little farther south and slower than the
EC-EPS/GEFS membership, so will be something to monitor with future
shifts. While the forecasted track is a little south from where we
usually like it for heavy snowfall across our CWA, that appears to
be offset somewhat by the track of the 500mb shortwave/low across
SD, and the similarly with the 700mb low (while model locations
vary, still appears to be in SD). Thus, we should have solid upper
level support for widespread precipitation late Thursday night and
into Saturday. The primary questions come down to how much QPF and
the P-Type. First for QPF, EC-EPS EFI data continues to highlight
this second wave with EFI values in the 0.6-0.7 range for Friday
into Saturday (slightly lower on Saturday). While the EC-EPS had
been a little lower on QPF 24hrs ago, definitely seen a trend up by
around 0.1-0.25" for the 24hr period ending 06Z Saturday. So the
going forecast has followed that trend with QPF trending upward,
which has consistency across all of the ensembles (traditional and
AI ones like AIFS-Ens/AIGEFS). Final position will depend on the
track of the upper low and moisture/lift on the north/west side of
it. This currently looks to be focused across northern and
especially north central SD at this point, with 48hr probabilities
of 0.5" of QPF over 75% across much of the CWA (decreases to 20-40%
chance of 1").

The focus then turns to P-Type for this event. Seeing an increased
FZRA potential for Thursday night (starting in central SD) and then
shifting east through Friday morning into east-central and northeast
SD and into west-central MN. This is tied to a warm air nose between
850-750mb that pivots through while surface temps are expected to be
below freezing. EC-EPS is the most aggressive on the freezing rain
potential from Pierre to Watertown area, while the GEFS is less
impressed on any RA/FZRA potential and only on the leading edge of
the precip. NBM P-Type probs have FZRA as the dominate p-type
through Fri morning in that Pierre to Watertown area, before the
warm nose erodes and snow becomes the focus. Once the p-type
switches to snow, should see it remain that way for the rest of the
event. SLRs will likely be in the 9-11:1 range for the event, and
with the current QPF amounts, our 48hr totals stretch from 4-8",
greatest over the northwest half of the CWA. Factoring in 25th-75th
percentile values from NBM v5.0, we`re looking at 2-4" range for
48hrs over the southeast part of our CWA, while the northwest is 5-
10" range. One item of note for our snowfall amounts is that they do
not factor in compaction or any melting from the ground, so they may
end up running a little high compared to final numbers. Of course,
we also still have a couple days for things to adjust/change too.
Finally, would expect us to need at least an advisory at this point,
but will hold off on any headlines at this point so we don`t have 4
day long product.

Beyond the system, a ridge over the western CONUS will become
established again and lead to northwesterly flow aloft over the
region. At this point, other than a weak shortwave brushing the
northeast part of the area on Sunday night, looks to be dry through
the rest of the extended forecast. With the expected snow on the
ground, should see temps slowly warming for the middle/end of next
week towards more normal values, but that timing will all depend on
how quickly the snow we receive melts.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1222 PM CDT Tue Mar 31 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR ceilings that have persisted this morning are expected to clear
out over the next couple of hours, giving way to VFR conditions
through the rest of the day today and into early tonight. The main
focus of this forecast is the incoming snow, which begins over
central South Dakota this evening and arrives over northeastern
South Dakota and western Minnesota early Wednesday morning. The
heaviest snowfall is currently anticipated over north central
South Dakota. Falling snow rates will be fairly light, less than
half an inch per hour expected. However, visibility reductions due
to the snow will be present, generally to MVFR/IFR conditions,
but perhaps as low as half a mile at times when combined with
winds gusting upwards of 25 knots.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 7 AM Wednesday to 7 PM CDT Thursday
     for SDZ006>008-011-018>023.

     Winter Weather Advisory from 1 AM CDT /midnight MDT/ Wednesday
     to 1 PM CDT /noon MDT/ Thursday for SDZ003>005-009-010-
     015>017-033>037.

MN...Winter Weather Advisory from 7 AM Wednesday to 7 PM CDT Thursday
     for MNZ039-046.

&&

$$

SHORT TERM...BC
LONG TERM...SRF
AVIATION...BC