621
FXUS63 KABR 211148 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
648 AM CDT Mon Sep 21 2026

.KEY MESSAGES...

- Bands of rain will continue this morning across the region,
  with the exception of far northeastern SD into west central
  MN. Rain will taper off northwest to southeast through late
  this afternoon. Rainfall amounts exceeding 0.25" is 40 to 55%
  along and south of a line from Eagle Butte to Watertown.

- There will be a brief break on Tuesday before spotty chances
  of rain returns Tuesday night across central South Dakota.
  Occasional rain chances continue Wednesday through the end of
  the week with the highest chances (50-80%) Wednesday
  afternoon through Thursday morning from north central through
  northeastern SD into western MN.

- Temperatures will remain near to slightly below seasonal
  averages through Tuesday before climbing above normal toward
  the middle of the week.

&&

.UPDATE...
Issued at 638 AM CDT Mon Sep 21 2026

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

UPDATE Issued at 348 AM CDT Mon Sep 21 2026

With heavier bands of rain falling across Spink County and
eastward, did up the QPF a bit over this area for higher
amounts potentially reaching a half inch through this afternoon.

&&

.DISCUSSION...
Issued at 123 AM CDT Mon Sep 21 2026

As of 1am the large and wavy ridge continues to our north and
beneath this, a persistent and slow moving upper level low is
spinning over southern/southwestern SD and northern NE border. This
is continuing to bring bands of rain showers to the region with the
bulk of the moisture over southeastern to east central SD with more
spotty precip over central SD as the bands tracks north and west per
counterclockwise flow. Through the morning, this low will continue
to track east and southeast along the border (and weaken) with the
open wave over ~NE/IA border by 21Z. As this system moves out rain
will diminish northwest to southeast (used a blend of
NBM/Conshort/ECAM) with the last of the rain exiting east central SD
this afternoon. QPF (or additional rain for some) ranges from around
a quarter to potentially half of an inch over portions of south
central to east central SD with QPF decreasing significantly, to a
couple hundredths of an inch to nothing, the further north and
northeast in the CWA due to the storm track as well as drier air
from a large mid level to surface high that resides over Ontario.
With the region on the western to southwestern side of this high,
overall dry conditions are expected tonight. Dry weather continues
Tuesday, however, weak shortwave energy (under the ongoing ridge)
will be over the region which will bring back some clouds to the CWA
and slight chances of pops over portions of south central SD in the
afternoon. With help from an increasing LLJ (25-35kts), the chance
of light rain spreads, as both EC/GEFS does highlight this. NBM
indicate spotty coverage of pops of 20-45% across central SD,
highest over far south central SD (mainly Lyman/Buffalo counties and
southward Tuesday night/early Wednesday.

As the high drifts off towards the east/northeast, a negative tilted
shortwave will track northeast (that developed over southern
CA/Pacific) and move in over the western Dakotas/MT/WY Wednesday
evening and tracking over ND/MN through Thursday morning. There is a
bit of a difference between the models on exact track and intensity
of this trough at this time. This will bring the return of moisture
to the area with models at this point having the precip move in over
north central SD Wednesday morning and becoming more widespread
across the CWA by Wednesday night (NBM pops 50-80%) with rain ending
west to east across the CWA by Thursday afternoon as the shortwave
exits the region. Again, timing between models varies a bit on when
the last of the rain exit with GEPS being the slowest. Probability
of 24hr QPF>0.25", ending 12Z Thursday is 35-65% from north central
through northeastern SD/western MN, highest over northern Corson
into ND and along and east of the Coteau. With this -PNA
pattern setting up for the end of the week, another shortwave
moves in for Friday (per southwesterly flow). This feature
interacting with southerly flow and pulling in moisture will
result in additional rain chances Friday/Saturday. Low
confidence in exact setup/track at this time and overall
coverage of rain. As of now NBM pops ranges from 20-40% along
and east of the Mo River and highest James Valley and eastward.

Our windiest day of the week will be Tuesday afternoon (west of the
Mo River of 20-30kts) as the high exits and increasing pressure
gradient on the back side of it and east of a lee front. This
increased gradient/development of a 30kts LLJ, the gusty winds will
spread eastward across the CWA through Wednesday afternoon with NBM
gusts between 20-35kts. Ongoing easterly flow at 850mb to surface
(and lingering clouds) will keep temps cool again today withs highs
in the upper 50s to the lower to mid 60s. Low level winds will be
more southeasterly for Tuesday, but with the high still influencing
the area, temps will only warm up a few degrees with highs overall
in the 60s. South to southwest flow (and high moves out) will lead
to temps warming back up to above normal with the warmer air
spreading eastward across the CWA for the end of the week with
highs in the upper 60s and 70s.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 638 AM CDT Mon Sep 21 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR cigs will be most prevalent at KATY/KPIR terminals
through the daytime hours today. KABR/KMBG terminals will see a
more prevailing VFR/MVFR ceiling through the day. Light showers
will continue to hang around through at least a portion of the
morning hours before slowly fading away. KATY/KPIR will hold
onto the light shower chances the longest. East to northeast
light to moderate winds can be expected today before turning
more southeast late in this forecast cycle.

&&

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

&&

$$

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