392
FXUS63 KABR 131137 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
637 AM CDT Sun Sep 13 2026

.KEY MESSAGES...

- Cooler than normal temperatures expected through Wednesday
  (highs in the 60s to low 70s) with the exception of a brief
  warmup on Monday (highs in the mid to upper 70s over much of
  the forecast area). A gradual warming trend will begin mid-
  week and continue through the weekend.

- Confidence is high on widespread rain and perhaps weak
  thunderstorms overnight tonight through Monday afternoon.
  Highest rainfall totals are expected along the US-212
  corridor, where totals may exceed one inch (40-60% chance).

- Strong northwesterly winds take hold behind a cold front
  Monday afternoon into evening. Along and west of the
  Missouri River, wind gusts will reach as high as 35 to 45
  miles per hour.

&&

.UPDATE...
Issued at 626 AM CDT Sun Sep 13 2026

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.DISCUSSION...
Issued at 154 AM CDT Sun Sep 13 2026

Monitoring the potential for some early morning rain showers this
morning. Area of focus is mainly over central South Dakota, although
there is some signal in model guidance for some rain over parts of
northeastern South Dakota and western Minnesota as well. There is a
fair degree of model consensus for these showers to develop and move
overhead beginning around 08-09Z and continuing through sunrise and
into the morning hours. Expecting only light rain out of these
showers, with little accumulation.

More robust chances for rain arrive Sunday night into Monday
morning. Ensemble medians for precipitation continue to increase,
and models have trended the heaviest precipitation further south as
well. The heaviest rainfall is now expected over parts of eastern
South Dakota, with medians up over an inch in that area. NBM
probability to see an inch or more for the 24 hours ending Monday
evening ranges from around 40 to 60 percent along the US-212
corridor. While no severe weather is expected with this rain, there
is some hint to some flooding potential due to heavy rain. The main
driver of this signal is a plume of strong moisture into the area,
and PWATs sit at around 1.5"-1.75" Monday morning. This would be
well over 90th percentile values for this time of year by about
0.25"-0.5". Given the warmth above the surface, the warm cloud layer
is expected to be somewhere between 11000-12000 feet, another
ingredient in the flooding formula. With forcing coming from a 50+
knot low-level jet, storm motion will likely be fairly quick,
meaning that a training storm setup will be necessary for flooding
to develop. Perhaps the greatest limitation is a lack of instability
in the area. MUCAPE values struggle to hit even 500 J/kg, so there
is much to be desired. All this to say that while flooding can`t
quite be ruled out, it does appear to be somewhat of an edge case
with otherwise benign rainfall. Latest Flash Flood Guidance values
still exceed NBM 90th percentile values, so in all likelihood
whatever rain falls, the ground will be able to handle. It should
also be noted that while there is currently a focus on the US-212
corridor, the recent shift southward should be a reminder that
further shifts of the axis of heaviest rainfall will still be
possible despite a limited time frame before the precipitation
arrives.

Behind the rain Monday morning, a cold front will pass through the
forecast area Monday afternoon. As the front passes, winds will turn
from southerly out ahead to northwesterly behind. These
northwesterly winds will increase to 20 to 30 miles per hour,
particularly along and west of the Missouri River. Gusts may exceed
Wind Advisory criteria at times, although the latest NBM guidance
keeps those chances (~20-50%, increasing moving northwest) over
Corson and Dewey Counties. While no product will be issued on this
shift, a headline may be needed with future forecast packages,
especially with the NBM`s tendency to under-forecast wind
speeds under a cold air advection regime.

Temperatures Tuesday will return to slightly below normal (highs in
the mid to upper 60s) after a brief warmup to near-normal on Monday.
Mid-week, a weak upper-level ridge begins to build overhead. This
will lead to a gradual warming trend through the end of the week.
Expect multiple shortwaves to make their way into the region and
bring additional chances for rain to the forecast area.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 626 AM CDT Sun Sep 13 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast with mid/upper level CIGS during the
first 18 hours of the TAF valid period. After 06Z Monday, the
return flow set up of strong south-southeast 15 to 25 knot winds
will be drawing low level moisture up into the region. This sets
the stage for some potential sub-VFR cigs, and perhaps even some
pockets of IFR fog, particularly over the KPIR/KMBG terminals.
A couple bands of light rain have developed over the region.
Have transitioned the PROB30 groups to TEMPO groups. By 15Z, the
majority of this light precipitation should be out of the area,
leaving conditions dry until later tonight when the next round
of showers with embedded thunder begin to develop and move up
into central and north central South Dakota. Light east winds at
or less than 10 knots this morning will eventually settle into a
southeasterly direction today and increase tonight to 15 to 25
knots with higher gusts.

&&

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

&&

$$

UPDATE...10
DISCUSSION...BC
AVIATION...10