040
FXUS63 KABR 091928
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
228 PM CDT Sun Aug 9 2026

.KEY MESSAGES...

- There is a Slight Risk (level 2 out of 5) for severe thunderstorms
late this evening through the overnight hours across central SD.
Large hail of 1 to 2+ inches in diameter and thunderstorm wind gusts
in excess of 60 mph are possible. However, considerable uncertainty
on whether storms will form or not exists due to disagreements upon
the models.

- There is a Marginal Risk, level 1 out of 5, for severe storms
across the entire forecast area for both Monday and Tuesday during
the evening and overnight hours. Main threats include large hail of
1 to 2" in diameter and wind gusts in excess of 60 mph.

- Wildfire smoke aloft is expected to persist the next several days,
however there is little potential for the smoke at the surface.

&&

.DISCUSSION...
Issued at 219 PM CDT Sun Aug 9 2026

West/northwest flow aloft continues over the region on the
downstream side of a low amplitude ridge over the western CONUS and
southwest of the ongoing large low/trough over the Hudson Bay. This
evening through the overnight hours, another weak embedded shortwave
(35-50kts) will move in out of MT/WY and track east/southeast across
the Dakotas/MN through Monday morning. At the surface the CWA is
sandwiched between a high to our north with an elongated northwest
to southeast frontal boundary along the lee of the Rockies (and
several weak lows along it) connecting to a wesFor
example HRRR/RAP do not show any development of storms, like at
all, with NAMNest keeping any convection over north central SD
while FV3 keeps convection over south central SD and south of
the CWA with more of a easterly track.t to east frontal
boundary, and its low, over the Central Plains. This leaves the
Northern Plains on the northern side of this system with east to
northeast winds at the surface to 850mb. WAA will filter in
overnight as these winds will shift south/southeasterly across the
CWA through Monday morning with surface dewpoints in the upper 50s
and 60s across the CWA.

Regarding potential convection tonight, the latest runs of the 12Z
models have backed off quite a bit on the development and evolution
of thunderstorms resulting in very low confidence in potential
outcome. Due to this, stuck with NBM for much of the near short term
in terms of pops. As of now, HREF mean indicates the development of
storms moving in over north central SD (around ~3-5Z), which is
about the same time we have weak shortwave pulses over this area. If
these cells do in fact form initially, the environment is favorable
for supercells as MuCape/MLCape is forecast between 1000-2500j/kg
(Rap higher with values 2500-3500 j/kg over potions of central SD)
with bulk shear between 40-50kts (again RAP higher at 50-60kts) and
steep mid level lapse rates between 7-8C/km into the cooler air
aloft. Given the elevated nature and parameters mentioned, large
hail will be the main threat early on, especially with any
development of elevated supercells or splitting supercells per
elongated hodographs above the surface. Within the Slight Risk over
central SD, the probability of severe hail is 15-29%, with a cig 1
hatch (2"+ in diameter potential), over north central SD, mainly
locations along and west of the Mo River. If additional convection
develops through the night, this could result in mergers and
clusters that could grow upscale as the system tracks east or
southeast. If this occurs, then the main threat would become
more of a damaging wind gust of 60-70 mph or potentially higher
gusts above 75 mph if a RIJ/bow forms. SPC highlights this
threat as well over central SD giving the cig 1 hatched (74mph+
wind threat) per SPC along and south of a line from Mobridge to
Redfield. However, the caveat to all of this is that everything
needs to come together and line up timing wise an there seems to
be quite a bit of disagreement between the CAMs as mentioned on
timing, storm mode, and track with the possibility of nothing
developing.

Not too much change in the pattern aloft for Monday and Tuesday with
the region in overall zonal to northwest flow. Weak embedded
shortwave/pulses will track east/southeast over the area Monday
evening into Tuesday morning and again Tuesday evening into
Wednesday morning in tandem with CAPE of 1500+j/kg and wind
shear 30+kts along with ongoing low level moisture. Higher
amounts of CAPE and dewpoints potentially in the lower 70s look
possible Tuesday afternoon/evening. The pattern of discrete
cells potentially growing upscale looks to continue, therefore
large hail and wind gusts of 60-70+ mph will be the main
threats. A Marginal Risk for severe weather is outlooked over
the entire CWA Monday and Tuesday. Otherwise, this ongoing
pattern results in chances of precip through the end of the
week. This flow will lead to ongoing smoke aloft with not much
in the way of near surface smoke. With this setup, temps will be
near normal (ranging in the 80s) with stronger CAA developing
for the end of the week (strengthening trough out east) with
highs a good 5-10 degrees below average and forecast highs in
the 70s!

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1206 PM CDT Sun Aug 9 2026

Terminals KABR,KATY,KPIR,KMBG

Smoke aloft continues through the TAF period, resulting in
ongoing hazy skies. VFR cigs are forecast through the end of
the TAF period as well. Winds are out of the northeast to east
and will switch to more southeasterly early Monday morning.
Isolated showers and thunderstorms are possible late tonight
into Monday morning that could pass over the KMBG and KPIR
terminals. However, differences between the models result in
low confidence especially in track and location of any storms
that may form. If storms can grow vertically enough and
strengthen, then large hail (potentially 2+ inches in diameter)
and wind gusts of 60-70 mph is possible.

&&

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

&&

$$

DISCUSSION...MMM
AVIATION...MMM