425
FXUS63 KABR 180112 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
812 PM CDT Mon Aug 17 2026

.KEY MESSAGES...

- There is a Slight Risk, level 2 of 5, for isolated to
  scattered severe storms this afternoon and evening along and
  east of a line  from Murdo to Redfield to Sisseton. Main
  threats are large hail, 1 to 2" in diameter, and wind gusts of
  60 to 70 mph. A tornado or two can not be ruled out. Brief
  heavy rainfall is also possible.

- There is a Marginal Risk, level 1 out 5, for isolated severe
  storms north of a line from Pierre to Aberdeen. These storms
  may form in the heat of the afternoon, but may also move
  through with a wave overnight. Main threats include 1 inch
  diameter hail and wind gusts of 60 mph. Brief heavy rainfall
  is also possible.

&&

.UPDATE...
Issued at 759 PM CDT Mon Aug 17 2026

Short term guidance suggests weak northerly low level flow will
eventually pick up tonight behind this broad surface trof
working through turning southwest winds to a more north or
northwesterly direction. Despite the ample low level
moisture/instability, deep layer shear and 100+knot upper level
jet streak in play aloft, the atmosphere has not been able to
muster widespread severe weather, thus far, this evening over
central/eastern South Dakota. Isolated/widely scattered storms
earlier produced some wind gusts/damage mainly along and west
river. A few storms held hail signatures in them for 30-60
minutes, give or take. Still a couple pockets of shower/weak
thunderstorm activity occurring over the CWA. But, by and large,
the most active/strong storms that could come into/come close to
this CWA are off to the west-northwest in the far western
Dakotas and Montana. Hi-Res CAMs highlight another round of
convection to work through the region later tonight. Meanwhile,
current SVA Watch #591 is in effect until 11 PM CDT.

UPDATE Issued at 647 PM CDT Mon Aug 17 2026

See below for an aviation forecast discussion for the 00Z TAFs.

&&

.DISCUSSION...
Issued at 108 PM CDT Mon Aug 17 2026

Two focus areas for storms in the next 24 hours. The west/northwest
flow regime remains in place, with a surface trough just east of the
Missouri valley. There is one upper wave on the way out on Water
Vapor, not really much of an upper level wave during peak heating
today (neutral flow), and a second wave that develops in response to
increasing flow aloft as a upper trough over Canada deepens.  As
such, CAMS are pretty inconsistent in coverage and locations for
convection during peak heating, with more coverage during the
overnight hours wave.  During the afternoon, we`re looking at around
2 - 2.5k j/kg CAPE between the RAP/NAM/HREF. Out west/central this
afternoon, the profiles indicate mid level moisture, deep dry
subcloud layers and skinny CAPE with the HRRR showing an
inverted-v type profile. West/northwesterly flow translates
into long/straight hodographs. Thus, the severe weather threat
may be a wind/hail combo out west/central and more of a
hail/splitting supercell environment in the east.

Some minor nuance impacts of the environment: Flow out ahead of the
surface trough is southwesterly as the surface high continues
to migrate southwards. This would trend us slightly warmer and
less humid in comparison to NBM typically. The HRRR appears to
capture this drying and more stable conditions on the east side
of the boundary. Southwesterlies, even if not that strong, also
typically results in longer/straighter hodographs in the low
levels which we are picking up at KATY in the NAM/RAP. Likewise,
0-1km SRH is limited to 100m2/s2 across western Minnesota, with
the Sig Tor parameter at 1 or less. As such, tornado
development may be contingent on storm interactions.

The eastern CONUS trough deepens, with a ridge out west
intensifying, strengthening northwest flow aloft. As such,
temperatures will remain close to what they have been over the last
several days which is near normal, with additional subtle waves
for Wednesday and late Thursday. That pattern may break down
during the weekend.

In regards to smoke impacts, there remains a steady stream of
elevated smoke coming in from the Pacific Northwest thanks to this
persistent flow aloft. During the day today, most of that is
expected to move across North Dakota/northern Minnesota, but will be
more directly overhead for Tuesday. Likewise Smoke intensity aloft
(how thick and thus how it will impact temperatures) has seen a
downward trend in comparison to a week ago. With the trough/frontal
passage later today, northerly flow off high pressure is pretty weak
and there isn`t a lot of fires in the source region of this airmass,
so there isn`t much of a concern though the HRRR/RAP both have some
lower concentrations coming into the west tonight.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 647 PM CDT Mon Aug 17 2026

Terminals KABR,KATY,KPIR,KMBG

Scattered thunderstorms are working over central, north central
and northeast South Dakota. Strong thunderstorm wind gusts are
the primary severe threat, although hail up to an inch is
possible, too. Most of this round of rain should be ended or
clear of the TAF sites by 06Z. However, regional radar and very
short term guidance suggests there could be an additional round
or two of storms working through the forecast area later tonight
after sundown. Southwest winds are switching to northwest
overnight as well.

&&

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

&&

$$

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