416
FXUS63 KABR 071036 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
536 AM CDT Mon Sep 7 2026

.KEY MESSAGES...

- There is a Marginal risk (level 1 out of 5) for severe storms over
central and northeastern SD and west central MN today. The primary
hazards in the morning and afternoon will be 1 inch in diameter hail
and 60 mph wind gusts. Additionally, the threat for a tornado or two
over east central SD cannot be ruled out. For the evening and
overnight, the primary hazard will be 60 mph wind gusts with small
hail also possible.

- Northwest wind 15 to 30 mph and gusts of 25 to 45 mph, low
relative humidity, and dry cured fuels may result in fire weather
concerns over north central SD on Tuesday.

&&

.UPDATE...
Issued at 535 AM CDT Mon Sep 7 2026

Updated for 12Z Aviation Discussion below. Also, did minor
tweaks to the PoPs to better align them with the areal coverage
of the thunderstorms that have developed in central SD.

&&

.DISCUSSION...
Issued at 130 AM CDT Mon Sep 7 2026

For today through Tuesday morning, there will be 3 different
causes of showers and storm chances from different forcings moving
through. There is a Marginal risk (level 1 of 5) for the storms
today to become severe, with slightly different hazards from the
different causes. For the first cause, an upper-level shortwave
moving along the upper-level ridge that continues to sit over SD
will help to provide upper-level support for scattered showers and
storms early this morning into the afternoon. Similar to the
previous mornings, a low level jet will be providing the main
support for development as it develops over warm air and moisture
advecting into central SD early in the morning, which then shifts
over northeastern SD and west central MN later in the morning and
into the afternoon. CAPE values during the morning are forecast to
be between 1000-2000 J/kg, which will help with the development of
elevated clusters of showers and storms in the weakly forced
environment. Lapse rates between 5-7 C/km as well as bulk shear
values between 30-45kts in the environment could help the storms to
become severe. With the elevated nature to the storms, hail up
around 1 inch and wind gusts of 60 mph will be possible.

Along the western edge of the moisture advection, there looks to be
a weak dry line/outflow that might develop during the afternoon into
the evening, which will be the second cause of convection
developing. This boundary looks to mainly move through southeastern
parts of SD, though portions of south central SD east of the
Missouri River and east central SD could be clipped by it. With a
strong pressure gradient over eastern SD helping to support the low
level jet sticking around into the afternoon hours as well as
stronger lapse rates helping to get those winds to the surface,
surface winds will be able to gust up around 30-40 mph over areas
east of the Missouri River. This will help to create a fair bit of
low level shear during the afternoon. While the weakly forced
showers and storms talked about will be elevated in nature and not
able to access this shear, the weak dryline/outflow moving through
in the afternoon and evening will be able to. Because of this, the
development of a tornado or two cannot be ruled out in these storm
after around 1 pm CDT over southeastern and east central SD. The
shear will also help the storms develop hail up around 1 inch and
wind gusts of 60 mph.

An upper-level trough will be pushing the upper-level ridge out of
SD Monday evening and overnight while also supporting a cold front
at the surface moving through Monday afternoon overnight into
Tuesday morning. This cold front will be the third cause of
convection that could produce showers and storms. While models vary
the timing of the front, it is forecast to move into central SD late
Monday afternoon/early evening and then move through northeastern SD
late evening overnight into Tuesday morning. The other causes of
convection will have used up a lot of the instability over southern
and northeastern SD through the day which will help to keep showers
and storms from developing when the front moves through those areas.
However, there will still be around 1000-2000 J/kg of CAPE over
northern SD and ND as well as a fair bit of moisture to get some
isolated showers and storms to develop over north central SD this
evening and far northeastern SD and west central MN overnight. The
environment will have weaker lapse rates while also having about 35-
50 kts of bulk shear in the atmosphere to help the storms become
severe. Since the storms will be forming along a frontal boundary
with a lot of shear, strong winds will be the primary hazard, with
gust up around 60 mph possible. There could also be some smaller
hail that develops, though it should be less than 1 inch.

After the cold front moves out Tuesday, a high pressure slips in
over southwestern SD. This helps a stronger pressure gradient to
develop over northern SD and ND, which will create stronger winds
aloft that could get to the surface during the afternoon. There is a
30-60% chance that there will be wind gusts greater than 35 mph
Tuesday afternoon over north central SD. Additionally, with colder
and drier air moving in behind the front, the relative humidity
values will be lower. Right now, models are showing humidity values
between 20-30% over areas west of the Missouri River. In areas where
the strong winds and low humidity values overlap, there will be some
fire weather concerns, especially with dry fuels already in those
areas. This potential should be watched over the coming model runs
as a Red Flag warning might be needed for portions of north central
SD. The past few model runs have shifted the stronger winds to the
north out of northern SD, and if they continue this trend, then a
Red Flag warning might not be needed. With drier air moving in,
central and northeastern SD and west central MN will be getting a
couple day break from all the weakly forced scattered showers and
storms that have been happening the past few days.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 535 AM CDT Mon Sep 7 2026

Terminals KABR,KATY,KPIR,KMBG

Main focus of the TAF period was to attempt to time out the
shower/thunderstorm potential through the afternoon. We do have
weak lift aloft, which has helped produce the showers and
thunderstorms in central SD. That should continue to lift to
the east-northeast through the morning and afternoon hours.
Confidence still wasn`t high enough at KABR to add tempo for
thunder. Think it will probably be a 1-2hr period, but with some
trends towards farther south, opted to keep the PROB30 going.
Otherwise, KPIR likely has a several hour period of showers and
occasional thunderstorms to start the TAF period. Both KPIR and
KMBG have also picked up a low end MVFR or high end IFR cloud
deck, but with all of the high clouds, confidence is low on how
long it will persist. Forecast models don`t really hold onto it
much past 14Z.

&&

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

&&

$$

UPDATE...SRF
DISCUSSION...12
AVIATION...SRF