402
FXUS63 KABR 161935 CCA
AFDABR

Area Forecast Discussion...CORRECTED
National Weather Service Aberdeen SD
235 PM CDT Wed Sep 16 2026

.KEY MESSAGES...

-There is a slight risk (level 2 of 4) for excessive and heavy
 rainfall across portions of central and northeastern SD and west
 central MN Thursday afternoon through Friday evening. This heavy
 rainfall may lead to flooding in some areas.

-Heavy rain is expected beginning late Thursday afternoon and continuing
 through Friday evening. The highest accumulations are expected
 over eastern and south central South Dakota. The probability to
 see two inches of rain or more reaches 50-70% over eastern and
 south central South Dakota (decreasing elsewhere as you move
 north and west).

-Near-normal temperatures continue today and tomorrow, as highs
 will be in the low to mid 70s across much of the forecast area.
 Friday and through the weekend will have slightly cooler
 temperatures, with highs generally in the upper 60s to low 70s.

&&

.DISCUSSION...
Issued at 219 PM CDT Wed Sep 16 2026

As of 2pm, there are currently some elevated showers moving over
central and northeastern SD. These showers will be moving east and
slowly dissipating through the afternoon into the evening. The
showers are being driven by a low-level jet moving over the warm and
moist air advecting into this area, and mixing in the atmosphere
could help to get the stronger southeasterly winds to the surface.
There is the potential for wind gusts to be up around 30-40 mph for
a bit this afternoon. As the jet dies off this afternoon, the winds
will weaken and showers start to dissipate.

After the showers move out this afternoon, precipitation chances
will stay out of central and northeastern SD tonight into Thursday
morning. During this time, the moisture will continue to advect into
the state both aloft and at the surface. This will help to prime the
environment for the next system to come in. A surface low will be
moving out of the southwest US tonight and into NE/SD Thursday into
Friday, with a frontal boundary moving into the area a bit before
the low. Some models show a few scattered showers moving in earlier
in the afternoon along this boundary while other models lack some of
the instability to develop anything along the boundary. In this
case, precipitation moves in along the northern and western side of
the low Thursday evening. The low then moves northeast through SD
Thursday night into Friday. The most current model ensemble runs
have shifted the track of this low system to the north slightly, by
a county or two, which has shifted the area with the highest
rainfall amounts. This shift in the track will need to be watched in
the coming ensemble runs to see if it continues to shift the
rainfall amounts to the north, or if they start to move it back to
the south.

Model soundings show saturated columns of moisture through the
atmosphere with tall, skinny CAPE profile over most of central and
northeastern SD. These sounding profiles are a good sign that the
environment will be able to support enhanced rainfall rates Thursday
evening through Friday afternoon. Models hint that some heavier
bands of rainfall will be possible Thursday night into Friday
morning taking advantage of the environment to dump the bulk of the
rainfall. There continues to be variability in the models for
rainfall amounts from a few different factors, such as the locations
and track of the system, where the bands of the heaviest rainfalls
occur, and how long the system sticks around some areas. This leads
to a larger spread, over 1 inch between the 25th to 75th percentiles
in some areas, in rainfall amounts and lowers confidence. The models
have been fairly consistent with the rainfall just barely glancing
north central SD, with between 0.25-0.75 inch of rainfall
accumulation expected. The models have also been consistent with a
bullseye of rainfall amounts occurring over east central SD
somewhere, where 1.5+ inches expected. Right now, the ensembles are
showing a 90% chance for areas in a line from Pierre to Redfield and
then Milbank, and areas in east central, to get an inch or more of
rainfall between Thursday afternoon through Friday evening and 50-
70% chance for 2 inches. With these rainfall amounts and the
potential for even more to fall in some areas, there is a slight
risk for excessive and heavy rainfall from the system. Since the
ground is fairly dry from the lack of precipitation, it should be
able to handle a fair bit of water, even after the rain we had the
other day. However, if the heaviest rain bands are slow moving or
continue to move over the same areas for a while, the heavy rainfall
amounts could start to impact low lying and poor drainage areas and
potentially even cause a little bit of flooding.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1215 PM CDT Wed Sep 16 2026

Terminals KABR,KATY,KPIR,KMBG

Some elevated showers continue to develop from a low level jet
and move near the KPIR terminal for a few more hours from some
scattered showers this morning. These showers should move east
and dissipate this afternoon. This low level jet is also able to
get some stronger winds mixed to the surface during the early
afternoon, with gust up around 25-35 mph at KPIR and KMBG. Once
this jet dies off during the afternoon, the winds will also
dissipate. The weaker winds will start to become more easterly
overnight before turning back to the southeast Thursday morning.
There are currently some lower VFR ceilings over some of the
terminals and it will continue for a little bit before clearing
and becoming taller VFR ceilings this evening or into the
nighttime. The winds will pick up again over KMBG and KPIR
Thursday, with gusts up around 20-25 mph possible.

&&

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

&&

$$

DISCUSSION...12
AVIATION...12