704
FXUS63 KABR 161117
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
617 AM CDT Sat May 16 2026

.KEY MESSAGES...

- Red Flag conditions again for portions of central South Dakota
  with afternoon humidity down around 20% and winds out of the
  southeast gusting 20 to 35 mph.

- Showers and thunderstorms returning starting Saturday night,
  continuing through Sunday, with rain persisting into Monday.

- Slight Risk (2 of 5) mostly focused across northeast South
  Dakota and west central Minnesota Sunday afternoon/evening.
  Marginal Risk for severe weather (1 of 5) includes parts of
  the northeast and central South Dakota. Main threats are large
  hail and a tornado or two.

- Colder air returns Monday and Tuesday, with high temperatures
  around 15 to 20 degrees below normal. Temperatures Wednesday
  morning may drop to near or below freezing.

&&

.UPDATE...
Issued at 617 AM CDT Sat May 16 2026

Updated for the 12Z TAF discussion below.

&&

.DISCUSSION...
Issued at 210 AM CDT Sat May 16 2026

Mild level warm advection responsible for some light returns on
radar and some clouds out in northwest South Dakota, migrating east,
however a deeper dive into the environment indicates a deep dry
subcloud layer below 10kft with dewpoint depressions about 20C all
the way to the surface.

As high pressure to the north migrates east, and a lee low develops
out west, return flow increases in strength. Still a very dry airmass
in place, with temperatures little changed in comparison to the last
few days. As such, despite the shift in wind direction, Red Flag
conditions once again for the western portions of the CWA.

CAMS show dry conditions continue through 03Z Sunday after which
broad area of weak shower/storm activity lifts into central/north
central South Dakota as mid level warm advection increases. The
northeast is closer to after 06Z. NAM BUFKIT profiles depict mainly
moist adiabatic lapse rates and shallow instability with a stronger
thermal gradient in the mid levels across the northeast. 1/2km winds
are southeast to northwesterly, so the nose of the low level jet may
support more vigorous precipitation across the western Dakotas,
something the CAMS may also be hinting at.

That initial round of activity will have lifted all the way into
North Dakota by 15Z Sunday with a gap in precipitation before
enhancement with the next southwest flow wave, posed along the NE/SD
state line at 00Z. Some CAMS do have the area in-between these
systems still generating moisture, as well as the NAM/Canadian. As we
move from 00-06Z, QPF shifts to along the northeast/southwest
oriented inverted trough that extends up into western Minnesota.
The GFS has this feature along the SD/MN state line, with the
NAM a little farther west.

NBM CAPE mean is around 500j/kg or less Sunday afternoon, and while
the NAM has a bit more elevated CAPE (1500j/kg), NAM BUFKIT shows a
stable low level airmass across the northeast. That said, strong
unidirectional shear within this elevated instability would still
support elevated supercells/large hail threat.  EC ensembles CAPE
tops out at 2k, GEFS up around 3.5k. Bulk shear ensemble mean
is around 50kts, and NAM/RRFS hodographs above the stable layer
(2km) continues to be generally/mostly straight line with
strong southwest mid level flow. Low level southeasterlies in
the NAM thus present a better shear profile for tornadogenesis,
however the linchpin is daytime heating with those NAM profiles
also indicating stable conditions even into Sunday
afternoon/evening.

When it comes to the cold airmass mid-week, using the 10th
percentile, in what would be a worst case scenario, NBM 7am
temperatures for Tuesday morning are down around the low 30s
across north central South Dakota. With the departing low,
surface winds in the NBM are still between 15-25kts, meaning
while temperatures will be cooler, its not likely a frost setup.
The focus for worst case scenario Wednesday morning is a lot
less localized and consists of the entire CWA down into the
upper 20s and low 30s. Again, that is worst case. The degree of
daytime heating driven cumulus that occurs in the more humid
cool airmass during the day Tuesday may also have an impact on
the temperatures that night. All that said, deterministic/mean
NBM has temperatures low enough to continue to warrant frost
mention.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 617 AM CDT Sat May 16 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will continue through the next 24 hours. Non-
diurnal wind are expected Saturday evening, with winds gusting
20-30kts by 03Z Sunday. Showers return after 06Z, with the best
chance of showers at ATY and PIR. Have kept the mention of
thunderstorms out of the forecast due to the low probability,
but they may be needed as the time nears.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 3 PM CDT /2 PM MDT/ this afternoon to 10
    PM CDT /9 PM MDT/ this evening for SDZ033>036-045-048-051.
MN...None.

&&

$$

UPDATE...10
DISCUSSION...07
AVIATION...06