029
FXUS63 KABR 120007 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
707 PM CDT Tue Aug 11 2026

.KEY MESSAGES...

- There is a Slight Risk (level 2 of 5) for isolated to
  scattered storms for the Missouri valley in the late
  afternoon and evening, and then a Marginal risk (level 1 of 5)
  for severe storms in northeast SD during the overnight hours.
  Main threats include 1 to 2 inch diameter hail and wind gusts
  of 60 to 70 mph.

- There is a Marginal risk (level 1 of 5) for severe storms to
  develop Wednesday afternoon through the overnight hours. Main
  threats include 1 inch in diameter hail and wind gusts of 60
  mph.

&&

.UPDATE...
Issued at 643 PM CDT Tue Aug 11 2026

Updated PoPs across Brown county and surrounding areas earlier
this evening to account for convection moving out of ND. Severe
Thunderstorm Watch 570 was issued earlier this evening as well,
for northern SD. Storm has since diminished after entering SD.
Otherwise, seeing scattered severe storms across the western
Dakotas which will try to approach the western CWA over the next
few hours.

&&

.DISCUSSION...
Issued at 135 PM CDT Tue Aug 11 2026

As of 18z, there are scattered afternoon cumulus clouds developing
over central and northeastern SD. Instability values of 2000-3000
J/kg this afternoon as well as a lot of moisture in the atmosphere
will help with storm development this evening into the overnight
hours. The main concern with the developing storms will be if the
weak forcing can get the storms to develop and stay alive into the
night. High-res models are showing the storms developing off of the
Lee of the Rockies surface trough in western SD late this afternoon
into the evening and then moving to the east/southeast into central
SD this evening into early overnight hours. The next question is if
there will be enough forcing to support the storms into the
overnight hours as they try to move through central and portions of
northeastern SD. This will come down to if the low level jet, as
some models have the jet develop and then support the storms through
the overnight hours while other models keep the jet from developing
and then the storms die off during the late evening. The models are
also showing the environment over central and northeastern SD has
elongated hodographs, which hint that the storms will become
splitting supercell. The splitting supercells are known to produce
large hail, and with the stronger lapse rates, there could be hail
up around 2 inches. Stronger winds are also possible, especially if
the low level jet develop, with wind gusts of 60-70 mph possible.
There is a slight risk (level 2 of 5) over central SD for storms to
become severe if they develop and a marginal risk (level 1 of 5)
over northeastern SD for severe storms if they move into the area.

The models are also hinting at some storms developing in ND early
Wednesday morning that could then move southeast into north central
or northeastern SD. There is currently lower confidence on this due
to the variability in the models, mainly from if there are stronger
storms this evening that will decrease the instability and stop the
storms in the morning, or if there are not storms that happen then
there will be more instability to support the storms in the morning.
Through Wednesday, the instability will be building over central and
northeastern SD. More storms are forecast to develop along the Lee
of the Rockies surface trough in western SD and ND Wednesday
afternoon and then move east and southeast through central and
northeastern SD during the late afternoon and evening. The NAM is
showing stronger shear values with these storms, but not very strong
lapse rates. This hints that very large hail will not be a large
threat. However, there is still a marginal risk (level 1 of 5) for
the storms to become severe with hail up to 1 inch and wind gusts of
60mph.

There will continue to be wildfire smoke aloft over central and
northeastern SD through today and into Wednesday. While this smoke
will likely only cause hazy skies across the area, there are some
areas east of the Missouri River that could get a bit of this smoke
to come to the surface, which could cause some problems to those who
are sensitive. Temperatures will be coolings slightly Wednesday,
with highs in the upper 70s to mid 80s. Wednesday night, colder
temperatures will be pushing in behind the the storms that move
through. This will help to cool the temperatures through the end of
the week into the weekend to be 5-10 degrees cooler than normal.
Highs will be in the 70s during this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 643 PM CDT Tue Aug 11 2026

Terminals KABR,KATY,KPIR,KMBG

Threat for TSRA exists across central SD (KPIR/KMBG) tonight,
and to a lesser extent over northeast SD (KABR/KATY). Outside of
any TSRA activity, expect VFR conditions at the start of the TAF
period, with smoke aloft remaining over the region. There may be
some patches of lower cloud cover (sub-VFR) that try to settle
in across portions of the region late tonight into early
Wednesday morning, but confidence in this is low at this time.

&&

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

&&

$$

UPDATE...TMT
DISCUSSION...12
AVIATION...TMT