623
FXUS63 KABR 231137 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
637 AM CDT Wed Sep 23 2026

.KEY MESSAGES...

- Spotty rain showers (30-55%) are possible through the morning,
mainly across portions of central SD to the James River. Additional
rain (60-90%) and weak thunderstorm expected midday through Thursday
morning with the bulk of the rainfall falling this evening and
overnight. Chance of rainfall of a quarter inch or more is 50-90%
mainly along and east of I29.

- Occasional rain chances continue for the end of the week with the
highest chances (50-85%) Friday evening through Saturday morning,
east of the Missouri River.

&&

.UPDATE...
Issued at 622 AM CDT Wed Sep 23 2026

The aviation discussion has been updated for the 12Z TAFS.

&&

.DISCUSSION...
Issued at 138 AM CDT Wed Sep 23 2026

The bulk of the low to mid level moisture (RAP 1000-500mb RH>70%) is
over southern SD through NE. This will continue to surge northward
(thanks to a 25-35kt southerly LLJ) interacting with a weak
shortwave aloft. Cams indicate this spotty potential for light rain
across portions of central SD through the James Valley with pops
diminishing by late morning or so as the shortwave continues to exit
to the northeast. Cams seem to handle this potential fairly well but
there is a difference in intensity/coverage area and how far north
these showers could go in the CWA. So low confidence on who will see
the rain with NBM highlighting the bulk of this (30-55%) over south
central SD and southward of the CWA. So pops may need to be adjusted
through the morning.

The main feature is the negative tilted shortwave that will be over
MT/WY by 12Z where it will track northeastward through Thursday
morning, clipping the northern half of SD in the process, with
southwesterly winds. At the surface, winds will continue out of the
southeast ahead of its weak surface low moving in over southwestern
ND this evening with another weak low developing over western SD.
With this forcing, and ongoing LLJ over central SD pumping in
moisture, models indicate precip moving in, mainly across north
central SD mid/late morning to even the midday. NBM is the most
aggressive with the rain moving in closer to 12Z while HREF mean
indicates more 15-18Z as ENS a bit slower on the rain timing entering
with GEPS being the quickest. So low confidence on exact timing. As
the system tracks northeast, and the low level jet eastward (and
weakens bit), rain chances also spread a bit eastward. Again HREF
mean and CAMS really keep this rain spotty along the WAA side of the
system this afternoon through the evening with the bulk staying
closer to the axis of the trough over ND. NBM is still aggressive
on pops so they may need to be adjusted as well closer to time.
Precip chances and coverage area does increase per CAMS/HREF
around ~04-06Z (thus increasing confidence) with the bulk of the
pops of 50%+ James Valley and eastward with 80%+ along and east
of the Coteau as drier air will already be moving in over
central SD on the backside of this system. This is in part to an
increase in southwesterly winds aloft at 700mb (25-30kts) and
the LLJ strengthening again to around 35-40kts pulling in that
moisture. During this time PWAT values are forecast to range
between 1.25-1.5" east of the Mo River and highest eastern SD/MN
which is about 3 standard deviations above climo per NAEFs. EFI
does highlight 0.5 to 0.7 Coteau and eastward with a SOT of
zero over far SD/ND/MN border meaning most members are near
reforecast climatology and not expecting anything too anomalous.
Probability of 24hr QPF>0.25", ending 18Z Thursday is 50-90%
James Valley and eastward, and highest along and east of the
Coteau. Prob of a half inch is 30-65%, again highest Coteau and
eastward. A few of the HREF members do show the potential for
weak thunderstorms as MUCAPE will be up to 750j/kg. However no
severe weather is expected. Any stronger rain shower or storm
will lead to the potential of higher QPF. We are also not
outlooked on ERO so flooding is not expected. As the system
continues into Canada and dry air spreads eastward Thursday
morning, pops will continue to diminishes west to east with the
last of rain exiting eastern SD/MN by mid to late morning.

Dry conditions are then expected through early Thursday evening.
Chances of precip returns Thursday night across the southern CWA
with this moisture spreading northward Friday per a south to north
tracking shortwave from the central plains. It then combines and
gets absorbed by a negative shortwave trough moving in from the
southwest (ahead of a large trough sitting over the PacNW). This
system will then track northeast across the region through Saturday
morning. The highest pops of 70-85% will be Friday evening through
Saturday morning, highest James Valley and eastward (thanks to a
strengthening southerly LLJ). Pops diminish west to east as the
system moves out by late Saturday morning. Could see another few
tenths of an inch of rainfall from this. As of now high pressure
moves in behind it with dry conditions expected for the rest of
Saturday and Sunday. This unsettled weather pattern setup continues
with precip chances again early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 622 AM CDT Wed Sep 23 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR cigs will remain a prevalent trend at all terminals
through this forecast cycle. Spotty -SHRAs will be possible at
KABR through mid morning or so with more numerous -SHRAs/-TSRAs
possible later this afternoon into tonight at all TAF sites. IFR
cigs and MVFR vsbys will be possible in the more steady, heavier
showers or storms. CIGs may begin to show some signs of
improvement late in the period across central SD and in
particular at KPIR. Expected a stronger southeast wind to
persist through the day and into tonight with gusts ranging
between 20-30 kts.

&&

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

&&

$$

UPDATE...Vipond
DISCUSSION...MMM
AVIATION...Vipond