212
FXUS63 KABR 101722 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1222 PM CDT Fri Apr 10 2026

.KEY MESSAGES...

- Around a 60% chance of light rain showers early Saturday over
  the Glacial Lakes region, with just a few hundredths of
  precipitation. 20-30% chance of light rain showers Saturday
  night (isolated to scattered coverage).

- Well above normal temperatures Sunday, highs in the 70s to low
  80s (15 to 25 above normal). West winds 25 to 35 mph.
  Grassland Fire Danger increases to High/Very High category.

&&

.UPDATE...
Issued at 1220 PM CDT Fri Apr 10 2026

See below for an aviation forecast discussion for the 18Z TAFs.

UPDATE Issued at 804 AM CDT Fri Apr 10 2026

Fog`s burning off. The rest of the forecast is in good shape. No
changes planned to the today period forecast.

&&

.DISCUSSION...
Issued at 1255 AM CDT Fri Apr 10 2026

Fog has developed over the recently acquired snowpack, with only 1-3
degree dewpoint depressions during the late evening and fog already
picking up on webcams and GOES nighttime microphysics. Its pretty
localized to mainly Highway 12 in Brown/Edmunds counties, and even
here through the last 2 hours has come and gone. Southwest low level
winds may provide enough mixing to counter cooling. No headlines at
current.

Today: Upper trough coming into the western CONUS, with a departing
wave to the east putting us into northwest flow initially, with a
broad ridge building in upstream and then overhead tonight. At the
surface we start with high pressure across the east of the state,
moving into the Western Lakes region later today. On the backside of
the high we see a developing pressure gradient, with the strongest
gradient west river through the afternoon (21Z) spreading east
overnight. The gradient tops out at 12-16 mb by Saturday morning
(09Z-12Z) and by then is more universally spread across the state.
For the day, with the surface high over the east, low level flow is
south southwesterly and not very strong. 850mb warm advection is
pretty weak as well. Lingering fog, and snow cover may make an
initial dent in holding back warming today, but not very confident
it will have a strong impact in comparison the the current NBM which
has highs in the 50s. We`re pretty close to the 50th percentile, and
its only about 3-4F between the 25th/75th so no good evidence to
shift one way or the other. Mixing overnight to keep us quite mild.
NBM deterministic is 2-4F warmer over the mean, also with a 3-4
degree spread between the 25th/75th percentiles. Lows in the 30s to
near 40 degrees represent 5 to 10 degrees above climo.

Saturday: Start the day with that pressure gradient and 1/2km winds
between 30 and 40kts. NAM BUFKIT mixed winds are around 20 to 30kts.
NAM/GFS and RRFS profiles also highlight a fairly stable boundary
layer. Aloft, a broad upper ridge has set up across the eastern
CONUS, putting us into a southwest flow regime. There is a very
subtle wave in the NAM moving across the CWA early in the day, with
a slightly stronger wave late in the day/early overnight. For most
of the day, the NAM BUFKIT profiles indicate the moisture associated
with the first feature is mostly above 10kft or trapped at 4kft
below the inversion. Even in the mid level deck, we`re only seeing a
few microbars of lift. There is an hour or two in there with full
saturation of the profile before mid levels dry back out again.
Deterministic models all show some output across eastern South
Dakota/western Minnesota. Going through the CAMS also indicates some
fairly light, sporadic moisture. NBM probability for moisture are
around 25% James valley and 50/60% for the Glacial Lakes region from
this setup. Output is only a hundredth or two and looking at the
profiles woudn`t be surprised if this is just scattered sprinkles.
May better refine the time range however, with CAMS pretty limited
before 09Z, peaking around 15Z and everything east by 21Z. Second
wave is only depicted as mid level moisture with in NAM BUFKIT
profiles with a deep dry and very warm subcloud layer. Deterministic
models also have much less precipitation output, with a dry GFS/NAM.
GEFS plumes are limited to 2 members, though these have greater than
0.1" with one member for Mobridge coming in with 0.65" suggesting
that we cant rule out some form of convection. NAM BUFKIT profiles
do show some weak, elevated CAPE to support this theory. For
temperatures Saturday, deterministic NBM is 4-5F below the 50th
percentile, with a 5-8 degree range in the 25th/75th percentiles.

Sunday: For the upper levels, there will be a subtle ridge coming in
from the intermountain west as a broad upper trough evolves over the
western CONUS. We also have the departing shortwave early Sunday
into east central North Dakota. A surface low associated with this
wave is located over western North Dakota to start the day, and
moves east. That results in westerly low level flow with a gradient.
Additionally, there is a plume of some very mild air aloft. Sunday
06-12Z, GEFS 850mb thermal anomaly peaks at 2 standard deviations
above climo and as such NBM temperatures are running 18 to 25
degrees above climo. Here`s the kicker! Deterministic NBM is in the
70s, tops out around 80, which is only about the 10th percentile.
But if we look at both NAM/GFS profiles, we see a very strong
inversion/warm airmass just off the surface, but that weakens
through the morning, countered by daytime heating later. The reason
ends up being the departing wave also takes the core warmest air
east. Westerly flow and weak cold advection would end up enhancing
mixing though, countering the loss of warmer air aloft. Not sure if
we`ll be making changes during this timeframe, but current NBM is
getting close to red-flag.

This is also the second day here with an deterministic NBM low bias
though one doesn`t exist for Today (Friday). As such, not sure where
to go with adjusting NBM.

Monday: Brief period of dry weather late Sunday into the first half
of Monday. Pattern appears to be split flow, with waves moving east
out of the 4 Corners region and a second in WY/MT moving through
ND/northern SD. NBM POPs increase to about 40% with this WY/MT
southwest flow shortwave, though we`re starting to see at this range
differences in placement/strength of the wave and associated surface
low locations. This timeframe is when we are SPC outlooked in the
east, but its too far out to start in on any details with
confidence. With the surface low potentially overhead or to the
south, outside the southeast CWA were into more stable and slightly
cooler northeast flow, with a thermal gradient from north to south.

Mid-Week: Its an active pattern with the 4 Corners wave lifting
northeast. Another wave coming into the Pacific Northwest starts
taking shape into the next upstream trough. 850mb temperatures and
anomalies point to seasonal, possible slightly milder in comparison
to climo.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1220 PM CDT Fri Apr 10 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected through 12Z Saturday. KPIR may end
up being the only terminal to remain VFR to the end of the TAF
valid period on Saturday. It`s really just going to depend on
where/when the low stratus develops Saturday morning. KABR/KATY
(and possibly KMBG) should be under these low clouds by 18Z
Saturday and are to remain so through the end of Saturday. Winds
will be gradually gaining strength, from a southerly direction,
through the rest of today and all of tonight. Expect wind speeds
overnight into Saturday to ramp up to 15 to 25 knots with gusts
of 25 to 35 knots. Also, mainly between 12Z and 18Z Saturday,
there are some low probability chances of light rain showers
over the KATY terminal; covered for the time being with a couple
of PROB30 groups.

&&

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

&&

$$

UPDATE...10
DISCUSSION...07
AVIATION...10