971
FXUS63 KABR 201124 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
624 AM CDT Sat Jun 20 2026

.KEY MESSAGES...

- Widespread rainfall Saturday evening through the day Sunday.
  Main focus area is central South Dakota. Probability of
  exceeding 1" rainfall is 70-90% along and south of a line from
  Eagle Butte to Fort Thompson. Potential rainfall amounts drop
  off dramatically with little if any expected east of a line
  from Aberdeen to Watertown.

- Faster moving system Monday night. Additional light amounts of
  moisture, but more convective in nature so low confidence on
  amounts. Severe weather unlikely.

- Temperatures remain near to slightly below normal through next
  week. Coolest day being Sunday at 5 to 20 degrees below
  normal.

&&

.UPDATE...
Issued at 614 AM CDT Sat Jun 20 2026

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

&&

.DISCUSSION...
Issued at 1242 AM CDT Sat Jun 20 2026

Fires in the Intermountain West have generated smoke which is being
advected up ahead of the next system. As such, looking at the HRRR
vertically integrated smoke, there is a plume that moves out over
South Dakota later today. Smoke is at relatively low concentration
as it moves into the state, and with low level flow off the high to
the north, non-existant at the surface. It may play some small part
in affecting high temperatures today, but at the low concentrations
in the HRRR will not adjust NBM temperatures.

Focus shifts to moisture associated with the wave that passes across
the area later today through most of Sunday. The wave is sandwiched
by jets to the north and south, resulting in a slow overall motion,
and that long duration will aid in the overall moisture amounts.
Synoptically, this is also mainly a rain-maker as profiles remain
moist adiabatic aloft, with some skinny CAPE, no shear, and an
inversion and a cooler low level airmass associated with flow off
the high into the system.

Forecast QPF continues to drop, and is down about an inch since this
time last night. We now fall just a little below the mean NBM, but
that still gives us greater than an inch moisture overall for
central South Dakota. Better refinement is evident across north
central/northeast South Dakota with much lower moisture potential
for Aberdeen/Watertown (few hundredths) and Mobridge still on the
periphery with 2/3". Again, focus remains across central South
Dakota with at least some drought relief, with the NBM probability
of exceeding 1" moisture around for Pierre at 80% and 2" at 40%.
Profiles for Aberdeen/Watertown continue to show quite a bit of dry
air on the northern periphery of the system, and probabilities drop
rapidly off after exceeding a tenth of an inch. So those (Pierre v
Aberdeen/Watertown) are the bookends. In-between much less
confidence in overall moisture potential.

A clipper system moves in late Monday as the next system. QPF focus
is across the western Dakotas & eastern Montana/Wyoming Monday
afternoon with a rapid transition to the east. Thus, a lot less
moisture potential with this system. Profiles are dominated by
skinny CAPE and weak wind shear below 500mb.  Not really much mid-
level thermal advection on the backside, nor a strong gradient. NBM
post frontal winds mix out at 20 to 30kts.

A stronger ridge, with a wave under the ridge type system for late
in the week. Northwest flow before that arrives, and 700mb
temperatures not being overly warm means we cant rule out continued
hit and miss weak thunderstorms during the interlude. With the mild
mid level temperatures and a northwest flow pattern most of the
forecast period, daily temperatures remain mild with low humidity.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 614 AM CDT Sat Jun 20 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions for KABR/KATY/KMBG through the TAF valid period.
Guidance has some MVFR cigs moving into KPIR, however, after 06Z
tonight. Light winds settling into an east-southeast direction
today, generally around 5 to 10 knots. Rain is expected to move
into the KPIR area later this evening and persist, off and on,
throughout tonight. Some of this light rain could even be
reaching up to the KMBG terminal prior to 12Z Sunday.

&&

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

&&

$$

UPDATE...10
DISCUSSION...07
AVIATION...10