074
FXUS63 KABR 050538
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1138 PM CST Tue Feb 4 2025

.KEY MESSAGES...

- There is a 40 to 65% chance of snow starting Wednesday afternoon
over northeastern SD and west central MN through Thursday morning.
Less than an inch of snow is expected. There is a slight chance (25%
or less) of freezing rain and/or sleet that could be mixed in at
times. Little to no ice accumulation is expected.

- Winds out of the northwest of 25 to 35 mph will result in some
blowing/drifting snow along and north of highway 12 Thursday.

- Our next chance of precipitation will be Friday into Saturday.
Probabilities of exceeding 6 inches have increased to 20-40% west
river/40-60% east river north of I90.

&&

.UPDATE...
Issued at 548 PM CST Tue Feb 4 2025

No significant changes have been made to the ongoing forecast at
this time. We`ll continue to monitor the temperatures, that will
be nearly steady through 15Z Wednesday.

&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
Issued at 201 PM CST Tue Feb 4 2025

As of 2PM, temperatures are still in the single digits as mid to
high clouds blanket the CWA and northeast to east flow at the
surface. Overall quiet weather expected heading into this evening
and tonight with this high to our northeast and zonal flow
continuing underneath a ridge aloft. As the ridge shifts east, mid
level flow will then shift out of the southwest as energy moves in
off the southern CA coast and tracks northeast, with a shortwave
setting up on the the lee side of the Rockies by early Wednesday
morning. This wave will track east over SD through the day. To the
east and northeast of this lee low, an inverted surface trough will
track west to east over the CWA as the center of this low will track
east/southeast and will be over southwestern SD/northwestern NE by
00Z Thursday. At the same time a low/shortwave will move across the
northern CONUS Wednesday evening through Thursday bringing
additional lift to the northern CWA Wednesday night into Thursday.
Behind these waves, another high pressure system moves in from the
northwest.

With this setup, CAMs/NBM do show the potential for precipitation
mainly over northern and northeastern SD into west central MN
Wednesday evening through early Thursday, with the highest chances
of precip (40-65%) between 00-12Z for this area as we will see
better lift. When looking at NAM/RAP soundings over the eastern CWA,
the consensus is that with southwesterly winds from 500-850mb, we
will have WAA with an apparent warm nose between 700-800mb (up to
2.5-3C), which will allow frozen hydrometeors (if they can form) to
partially melt (even totally melt!). Right below this, from around
5000ft to the surface, the column goes to below freezing (being in
this colder air mass). So having this warm nose aloft and the large
cold layer towards the surface does support the potential for sleet.
However, the column really does not fully saturate (with this weak
first shortwave) until later on in the evening, with the northern
wave. So any dryness in the lower to mid level would allow for
evaporation of the hydrometeors. Freezing rain/drizzle is also
possible if we can saturate and get precip below this warm nose in
the cold dome near the surface. So lots of questions therefore
confidence remains low on exact outcome and ptype. Latest NBM Ptype
does show about a 15-20% chance for freezing rain and 15-30% chance
sleet Wednesday afternoon/evening along with the snow. The column
does saturate better starting Wednesday evening and with CAA
filtering in on the backside of the system, Ptype should change to
all snow. Any snow will be light with less than an inch is
forecasted for this time period and little to no ice accumulation.

Temps will be a bit "warmer" than the past previous nights with
southeast flow at 925mb and clouds will help blanket the area. Snow
covered areas will remain chillier though. Overnight lows will range
from the single digits to around 12, warmest over south central SD.
Highs for Wednesday will be a bit warmer ranging in the 20s to even
the lower 40s over south central SD.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 201 PM CST Tue Feb 4 2025

The upper level pattern features a mainly west to east upper level
jet running coast to coast at between 120 to 145kts, and that
doesn`t really start to buckle until late in the weekend.

Main focus is on the late Friday/early Saturday system, with good
model agreement adding confidence that this will be an impactful
system, with the main question being to what degree?

First, will need to briefly look in on Thursday, which will feature
low level cold advection and a pressure bubble out west at the start
of the period. The surface gradient peaks a little earlier at about
10mb across the state. NAM BUFKIT soundings point to the cold
advection mixed winds for a few hours into the 30-40kt range along
with steep low level lapse rates in the afternoon. NAM probability
of exceeding 30mph hits all the ridge tops at between 30-60%. It
also identifies the trend that there is a surge with the initial
front/cold advection/pressure bubble followed by a lull and then an
increase with daytime heating. Will leave in mention of blowing snow
along and north of highway 12 where snow accumulations exceed an
inch.

So back to the main concern. We will already have a fairly cold
airmass in place being on the north side of the Arctic front late
Friday. The system is on a relative fast west to east trajectory
from the central Rockies late late Friday, across the state and on
into the Midwest by Saturday PM. NBM p-type is still predominantly
snow, with probabilities for exceeding 6 inches is now running at
around 20-40% for the Missouri valley and 40-60% east river north of
I90. Winds at least will be less impressive with this system with
only a 20-60% of exceeding 20mph. Thus blowing snow won`t be as much
of an issue overall.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1138 PM CST Tue Feb 4 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will continue for much of the time period. There
are 2 chances for mainly snow Wednesday afternoon and again in the
evening. The afternoon precipitation will be mainly over
northeastern SD (ABR/ATY), with the 2nd wave moving west to east
from MBG around 00Z to ABR around 02Z and then east to ATY. While
chances remain low, it was enough to add Prob30 to the forecast
for MVFR conditions including visibility restrictions of 5-6SM.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...KF
SHORT TERM...MMM
LONG TERM...Connelly
AVIATION...KF