901
FXUS63 KABR 010659
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
159 AM CDT Wed Apr 1 2026

.KEY MESSAGES...

- The first of two upcoming winter systems moves into the region
this morning and continues through Thursday evening. Snow amounts of
4 to 8 inches is expected north of Highway 212, with the highest
snow totals over the Leola Hills and the eastern slopes of the
Sisseton Hills. South of Highway 212, 0.5 to 3" of snow is expected.
A Winter Weather Advisory is in effect for all counties (except
Jones, Lyman, and Buffalo) through Thursday.

- Freezing rain is possible late this evening through Thursday
morning to parts of eastern South Dakota, particularly in the
Watertown area. While confidence is low, portions of Day/Clark
Counties and eastward through Grant/Deuel Counties may see upwards
of a tenth of an inch of ice.

- Strong easterly winds will gust up to 25 to 35 miles per hour
today, 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, today
in particular. No whiteout/blizzard conditions anticipated.

- 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. Probability of 6" of snowfall or
more is 60 to 95% along and northwest of a line from Eagle Butte to
Sisseton, highest over north central SD. Probability of 8" or more
of snowfall is 40 to 75% for this same area, highest over north
central SD. Freezing rain will be possible Thursday night into
Friday morning along and south of Highway 212.

&&

.DISCUSSION...
Issued at 144 AM CDT Wed Apr 1 2026

The main concern will be the back to back systems that will bring
accumulating snow, rain, and the potential for freezing rain.
Temperatures during these events will play a key role in exact
precipitation type along with where the freezing line ends up. The
onset of precipitation with this first event will need to overcome
dry air so precip may be spotty to begin with before the entire
column saturates later on today and better forcing aloft. So low
confidence on snow amounts and exact Ptype at this time. Once the
system is upon us and we know exactly what is going on, several
updates to the forecast may need be needed. So make sure to stay
up to date!

Today Through Thursday Evening (System #1)

Both HREF along with GEFS/ENS are in agreement on the shortwave
aloft, with the axis over the southwest US by 12Z this morning with
the CWA on the downstream side of the trough in southwest flow.
Through this evening, this shortwave will track eastward then
northeast as it becomes more negatively tilted over the central
Plains by Thursday morning. Not too much change in the models as
the surface low will be over WY this morning where it will track
southeast (and deepen) along the lee of the Rockies over Colorado
by this evening. Models are somewhat consistent on the placement
of this low, however, intensity does differ a bit, anywhere from
993 to 996mb (GEFS/CMC are the lowest). Through the overnight,
this low will track eastward across southern NE/KS with the low
over NE/KS/IA border by 12Z Thursday and continuing to track
northeast and over MN/IA by 00Z Friday. GEFS is just ever so
slightly more north and east with this low than ENS and a faster
track. EC AI has a more southern track. Upper level support looks
to really be from the 700mb low that will track across SD as the
upper shortwave is displaced more south. In terms of moisture,
PWAT`s are about 2-3 standard deviation above climo with IVT about
2-3 above climo, however, this is more south of the CWA.

So precip wise, CAMs indicate rain and snow will move in over south
central SD this morning with precipitation spreading east/northeast
across the CWA through this afternoon as the CWA will be on the
northeast/northern side of this low. It may take some time to
initially start (or be spotty) as a few of the CAMs do show this,
especially HRRR as there is dry air to overcome with this high
pressure system and less forcing early. As it shifts east so will
this dry air and we see better overall coverage in precip this
evening. As temperatures do warm above freezing, precipitation will
change to rain or a rain/snow mix. CAMS do vary on where this
freezing line ends up. For example by 00Z, NAM/NamNest/RAP keep
mainly snow over north central SD while rain or rain/snow is south
of here. On the other hand, HiRESARW keeps temps cooler where mainly
all snow is falling and really only rain over south central SD. HREF
ensemble by this time show mainly all snow with the exception of
south central SD with ptype being rain. As I will say several
times, type will be temp dependent. Models do indicate a warm
nose aloft (ENS quite more aggressive in this compared to GEFS)in
which freezing rain will be possible over east central SD late
this evening through Thursday morning between the warmer air/rain
to our south and colder air/snow to our north, mainly Day/ Clark
and eastward through Deuel County, as most of the CAMS indicate
this along with HREF FRAM. As temperatures cool below freezing and
we are then on the wrap around side of the low, snow will
continue over the CWA through Thursday morning (and possible
ongoing freezing rain over east central SD before the column
cools) and exiting the far northeastern CWA by Thursday afternoon
or so. So to reiterate, ptype will be HIGHLY dependent on exact
temperatures as ENS is a bit cooler on temps than GEFS but only by
a few degrees as highs today will range in the 30s to around 40.
So PType could switch from rain to snow and vice versa, or a mix,
very quickly. NBM 25-75th spread in 2m temps is about 2-4 degrees,
increasing to 3-6 degrees this afternoon and evening with the
highest spread over south central SD, and back to 2-4 overnight
through Thursday. Also another caveat is the warmer temps lately
so NBM is most likely running on a warm bias, so if temps are
cooler than NBM,we could see more snow overall then rain. With
collab from surrounding offices, we did lower highs for
today/Thursday to match better with the HREF/global models. So
overall low confidence on snowfall amounts and exact Ptype with
this system.

So as mentioned the bulk of the precipitation will fall this evening
through Thursday morning. The good news is we certainly need this
moisture. GFS QPF amounts through 00Z Friday indicate 0.4 to 1.25"
from Jones County northeastward through Marshall and eastward with
amounts increasing the further east your go, with the highest
amounts over east central SD. EC ranges from 0.6 to 0.9" for this
same area. Canadian and NAM keep the higher QPF southeast of the CWA
with the highest amounts of 0.4 to 0.6" over far east central SD.
New run of NBM QPF lowers amounts west of the Mo River with amounts
of 0.4 to 1" east of the Mo River, highest along the eastern slopes
of the Coteau due to easterly winds/upslope flow. With temperatures
hovering around freezing to a bit above, snow ratio will average
around 10:1, a bit lower over the southern CWA. So latest snow
totals actually decreased amounts given the possibility of warmer
temps/more rain with deterministic amounts of 0.5 up to 8", lowest
over south central and highest along eastern slopes of the Coteau
and Leola Hills. Probability of 6" or more is about 50% for this
area and 30% for 8" or more (mainly Leola Hills). The best case
scenario (more rain/track is further south and east) 10th percentile
amounts range from 0 to 3 inches. If temps are cooler and ptype is
more snow or a more north and west track, 90th percentile will be 2
to 10 inches, lowest over south central SD and highest Leola
Hills/Coteau. NBM is a bit lower than WPC at this time with both
QPF/Snow totals on the order of an inch or two for any one location
across the CWA. EC EFI does highlight values of 0.5 to 0.7 and SOT
of zero right over the Leola Hills area for today with values of 0.6
to 0.8 east of the Mo River for Thursday, highest over eastern SD
with a SOT of zero here.

With the snow totals, it has been quite warm over the past several
weeks with zero frost depth meaning most of the ground is thawed.
For at least the onset of the event, there may be some help from the
warm ground in preventing snow from sticking on sidewalks and
roadways until it cools further. There will also be plenty of time
for compaction to limit the accumulations. So while upwards of 6-7"
may fall to the ground, confidence is low on actually seeing these
higher amounts and the associated impacts. Snow rates per HREF
indicates up to a half inch per hour but only over north central
SD later on this morning and again along the eastern slopes of the
Coteau overnight, otherwise expect a tenth to quarter of an inch
snowfall per hour. This also will help lessen any chances of quick
accumulating snow on roadways. Ice amounts have really not
changed ranging from 0.02 to potentially a tenth of an inch over
east central SD, highest from Day/Clark and eastward through
Grant/Deuel County. Again with the ground being warm, this may
form on grassy surfaces, trees, cars, etc.

Luckily winds both at the surface and aloft will not be terribly
windy with winds out of the east gusting between 25-35mph today
and up to 30 mph Thursday. With a lack of any fresh snow on the
ground, the latest run of the BLSN model shows drifting to
isolated areas of blowing snow, which may reduce visibility at
times, however, blizzard/whiteout conditions are not expected due
to lower winds and lower snowfall rates, as mentioned. With the
snow being wetter it will also cut down on being lofted. If
traveling, please still use caution as WSSI indicates Minor
Impacts over much of the CWA with moderate impacts along the
eastern slopes of the Coteau and portions of Leola Hills per
higher elevations and higher snow totals Today and Thursday.

No changes made to the headline as a Winter Weather Advisory is in
effect for the entire CWA, with the exception of James, Lyman, and
Buffalo Counties.

Early Friday through Saturday (System #2)

As the shortwave from the previous storm exits the region Thursday
evening, a small and quick low amplitude ridge will build over the
region early Friday morning before a large mid level low, centered
over WY by 12Z Friday with the CWA returning to southwest flow ahead
of this system. This closed low will track eastward across the
Northern Plains through Saturday, with the CWA on the backside of
this low by Saturday afternoon. Its surface low is very similar to
this first system as it forms over WY with the area of low pressure
dipping southward with a lee of the Rockies low forming Thursday
night/Friday morning. It will then track across NE/KS and track
northeast through IA/MN by Friday evening. ENS a bit further north
with the track of the low where ENS-AI has the low over KS/OK/TX
border by 12Z Friday and continuing with a more southerly and slower
track. So confidence is low on track and intensity at this time.
Enough support aloft with the 700mb low/shortwave will cause for a
more widespread precip event late Thursday night/early Friday
morning through Saturday afternoon. Rain, snow, and freezing rain
looks likely as the models all really indicate this freezing rain
potential Thursday night/Friday morning with the EC model being the
most aggressive. Ensemble indicates quite the warm nose at 850mb
(ranging from +1 to +4) at 850mb along and south of highway 212
early Friday morning, then northeastern SD/western MN before cooler
air filters in on the backside of this low/wrap around (ptype
changing to all snow as column cools) with surface temps below
freezing.

NBM prob of freezing rain is about 20-40% over central SD early
Friday morning transitioning to along and east of the Mo River 09Z-
12Z and James Valley and eastward 12-18Z before diminishing. Overall
QPF amounts range from 0.4 to 0.8" per NBM, highest over central SD.
As of now, the highest snow amounts look to be over north central SD
with amounts diminishing south and southeast over the CWA.
Probability of 6" is 60 to 95% from Eagle Butte through Sisseton and
northwest. Prob of 8" is 40 to 75% for the same area, again highest
over north central SD. Probability of 0.10" of ice is 40 to 60%
along and south of HWY 212 and Coteau eastward. Just like the
previous storm, SLR`s will be on the lower end ranging from 8-11:1,
increasing to around 14:1 Saturday morning as that colder air
filters in. WSO probability of exceeding warning criteria coincides
to where the higher snowfall is expected over north central SD with
probability at 50-80%. No headlines have been issued yet for this
second system as we will wait for this first system to pass.
Headlines will be issued either next shift or the shift after.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1231 AM CDT Wed Apr 1 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail through the early morning hours at all
TAF sites. Chances for light snow will begin to increase at
KPIR/KMBG closer to a 10Z-12Z time frame later this morning and
then continue in an on/off fashion through the remainder of the
morning hours. Some blowing snow will be possible as east winds
gust to around 25 kts. Light snow may become more steady during
this afternoon into tonight and become mixed with rain at times at
KPIR. MVFR/IFR CIGs and VSBYs are expected closer to midday and
prevail through the remainder of this forecast period.

Light snow chances spread east into the KABR/KATY areas later in
the day, moreso during the afternoon hours and then into tonight
through the end of this forecast cycle. Light snow will become
mixed with rain by late this afternoon into tonight with MVFR/IFR
CIGs and VSBYs becoming more prevalent with time. Easterly winds
will also gust to around 25 kts late this morning through the end
of this forecast cycle.


&&

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

     Winter Weather Advisory until 1 PM CDT /noon MDT/ Thursday for
     SDZ003>005-009-010-015>017-033>037.

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

&&

$$

DISCUSSION...MMM
AVIATION...Vipond