548
FXUS63 KABR 020821 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
321 AM CDT Thu Apr 2 2026

.KEY MESSAGES...

- Snow will diminish southwest to northeast across the region
  later on this morning through late this afternoon. Additional
  snow accumulations of 1 to 4 inches expected mainly over the
  James Valley and eastward through west central MN. Light icing,
  up to a tenth of an inch, remains possible over portions of east
  central SD.

- Increasing confidence on heavier snow Friday into Saturday, with
  amounts in excess of 6 inches over the northern portions of SD.
  Confidence is also increasing on the freezing rain potential
  where icing amounts between a tenth to potentially a quarter of
  an inch is possible, with the higher amounts over the southern
  half of the region. A Winter Storm Watch remains in effect for
  northern SD into west central MN.

- Temperatures staying below normal until perhaps Wednesday of next
  week.

&&


UPDATE Issued at 224 AM CDT Thu Apr 2 2026

Radar indicates that most of of the snow has diminished over
Corson and Dewey Counties with light snow continuing over Stanley
County. Have cancelled the Winter Weather Advisory for these
counties. The Winter Weather Advisory remains in effect for
counties east of the Missouri River.

&&

.DISCUSSION...
Issued at 131 AM CDT Thu Apr 2 2026

The main highlight will be one system exiting the region today and
the next one moving in late tonight through Saturday, bringing
accumulating snow and the potential for freezing rain/sleet. As of
midnight, the surface low is over western Kansas with its negative
tilted shortwave over eastern Colorado through NM. Current radar
indicates light to moderate snow falling over much of the CWA as it
tracks northeastward with temps hovering right around the freezing
mark for much of the area.

By 12Z, global and HREF ensembles agree on the negative tilted
shortwave continuing to track eastward over the Central Plains with
its nearly stacked 850mb to surface low over NE/KS/IA/Mo border.
This system will then track northeast through IA and over WI and
Michigan late tonight. With the CWA on the northern quadrant of this
low, CAMs/NBM are pretty consistent on mainly snow continuing to
fall with the possibility of rain mixing in over our far southern
CWA. There is still the potential this morning for freezing rain
and/or sleet mixed in over east central SD as a warm nose sets up
aloft for a few hours per NAM/EC soundings. However RAP/GFS keep the
column colder. So it will be all based on temps within the warm nose
and the surface. NBM probability of freezing rain over here is about
20-45% between 9-16Z and prob of sleet up to 50% (more Grant/Deuel
Counties). As colder air filters in aloft on the backside of this
low, precip will then change to all snow. CAMS/NBM indicate precip
will end southwest to northeast across the CWA with the last of the
snow chances over far northeastern SD/western MN late this afternoon
or early evening. Additional snow amounts of 1-4" possible James
Valley and eastward, highest over far northeastern SD/western MN.
Half inch to 2 inches is possible along and west of the Mo River.
Ice amounts up to a tenth of an inch possible, especially over
southeastern Hamlin into Deuel Counties. The Winter Weather
Advisory remains in effect through 1PM CDT for central SD (except
the southern 3 counties) and 7pm James Valley and eastward.

Our attention then turns to our next system coming in hot right
behind this system. Water Vapor imagery as of midnight indicates
quite the large mid level moving off the coast over
Washington/Oregon. It will track eastward across the Rockies today
(and deepen) with this nearly stacked low over the western
Dakotas/eastern MT/WY by 12Z Friday. This puts the CWA on the PVA
side of this low/downstream side of shortwave in southwest flow.
Then we start to split as the elongated surface low extending from
WY southeastward through CO becomes the main surface low that will
track east early Friday morning over ~NE/KS border with the 850mb
low tracking across the Northern Plains. ENS-AI has the track of the
lows more southward with ENS/GEFS actually in pretty good agreement.
The surface low and its upper level low plowing through the Dakotas
along with a good amount of moisture (PWAT values run about 1-2
standard deviations above climo and the northeasterly WV transport
into the Northern Plains) will bring more snow and ice.

Models indicate precipitation will move in over far central SD,
mainly along and west of the Mo River late tonight and will spread
eastward across the CWA through early Friday morning. NBM indicates
mainly a rain/freezing rain mix, and maybe even sleet, over central
SD late tonight with freezing rain becoming the dominant ptype
(warm nose between 800-700) east of the Mo River by 12Z (with
maybe some rain over south central SD). As the freezing rain/sleet
tracks east over the James Valley we start to see the colder air
filter in behind it as the main ptype will become snow over
central SD. As the freezing rain moves out with the track of the
low this snow will overspread the CWA as we sit within the
northern/northwest quadrant of the low especially over northern SD
where the deformation zone looks to line up. Also, with the 850mb
low tracking across the CWA and backside of the surface low, the
majority of the CAMS does indicate a dry slot setting up over
central SD to possibly east central SD around 14Z-22Z before the
wrap around snow moves in. NAMNest/HiRES shows this dry slot
extending well northward over the CWA while others do not. NBM has
not really picked up on it yet. So low confidence right now on
the position exactly of this dry slot. If this set up, this will
help lessen snow totals a bit. Snow will fill back in on the wrap
around part of the low, with the northern half of SD into ND still
within the deformation zone that looks to extend through northern
MN. With such a tight gradient, a northerly track of the low
would put the higher snow totals/deformation zone more into ND and
southerly track would bring the higher snow totals more south.

QPF amounts really only decreased slightly with the latest NBM but
still quite hefty ranging from a half inch to nearly 1.25", highest
over north central SD. Snow totals have diminished every so slightly
with amounts potentially of 5 to 10"+ inches north of highway 212,
with the highest accumulations along the ND/SD border. EC EFI
highlights this well with values of 0.7 to 0.9 and SOT of zero over
north central SD for snowfall and QPF. Probability of 8" is 60 to
80% north of highway 212, highest over north central SD. Prob of 12"
is 30-55% along and north of HWY 12. Worst case scenario (high end
amounts) could be 12-20" north of HWY 212. HREF does indicate the
potential for 3/4 to an inch/hr snowfall rates over north central
SD/ND border Friday morning with this threat shifting eastward.
This could lead to quick accumulating snow within this deformation
zone as the snowband probability tracker highlights this as well.
There has been an uptick in ice accumulations over the CWA,
helping to increase confidence as models have been consistent with
this the past couple of days. Probability of ice>0.10" is 50-75%
from a line and south of Gettysburg to Watertown and prob of 0.25"
is 20-30% highest over eastern Hughes/Sully through Hand/Hyde
Counties. A Winter Storm Watch remains in effect across the
northern half of the CWA, however, a Winter Weather Advisory or
even a Winter Storm Watch may need to be issued for the southern
half of the CWA for this ice potential. Will hold off on any
new/upgrading headlines on this shift.

Winds generally will increase on the backside of this low late
Friday night into Saturday. Lack of CAA will keep down the potential
for higher gusts with this being more of a steeper pressure gradient
scenario so kept with straight NBM for now. As of now, gusts of 25-
35 mph is possible. With the snow being heavier/wet this will help
cut down on it being lofted, however, the latest BLSN indicates
drifting to isolated areas of blowing snow more on Saturday which
could reduce visibility at times. No whiteout conditons are expected
at this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1242 AM CDT Thu Apr 2 2026

Terminals KABR,KATY,KPIR,KMBG

IFR CIGs and MVFR/IFR VSBYs will remain prevalent at all terminals
through this forecast cycle. Cannot rule out LIFR CIGs at times as
well. -SN/SN should be the more prevailing condition at
KABR/KMBG. A -RASN/-SNRA situation will be possible at KPIR and
KATY with the potential for even -FZRA/FZRA at times through the
early to mid morning hours, although KATY will have a better
chance to see this freezing precipitation versus KPIR. There will
be a lull in the precipitation by midday through the afternoon at
all terminals before the next wave of precipitation moves into the
KPIR/KMBG areas near the end of this forecast period.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 7 PM CDT this evening for
     SDZ006>008-011-018>023.

     Winter Storm Watch from Friday morning through Saturday evening
     for SDZ006>008-011-018.

     Winter Storm Watch from late tonight through Saturday afternoon
     for SDZ003>005-009-010-015>017.

     Winter Weather Advisory until 1 PM CDT this afternoon for SDZ004-
     005-009-010-016-017-034>037.

MN...Winter Weather Advisory until 7 PM CDT this evening for MNZ039-
     046.

     Winter Storm Watch from Friday morning through Saturday evening
     for MNZ039.

&&

$$

UPDATE...MMM
DISCUSSION...MMM
AVIATION...Vipond