778
FXUS63 KABR 091721
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1221 PM CDT Tue Jun 9 2026

.KEY MESSAGES...

- There is an Enhanced Risk (Level 3/5) for scattered to
  numerous severe storms for all of central and northeastern SD
  into west central MN this afternoon through tonight. Main
  threats include tornadoes (max intensity EF2+), large hail (2+
  inches in diameter), and wind gusts of 75+ mph. Heavy rain
  that could lead to flooding is also a threat.

- There is a Marginal Risk (Level 1/5) for isolated severe
  storms Wednesday afternoon and evening along and east of a
  line from Britton to Brookings. 1" hail and 60 mph gusts are
  the main threats.

&&

.UPDATE...
Issued at 1220 PM CDT Tue Jun 9 2026

Aviation discussion below has been updated in accordance with
the 12Z TAF issuance.

UPDATE Issued at 935 AM CDT Tue Jun 9 2026

No changes in the forecast have been made this morning, with the
main near-term concern of fog having mostly dissipated by this
point. Focus remains on the severe weather potential beginning this
afternoon. Current expectations are for storms to develop west of
the Missouri River between roughly 4-6 PM CDT, continuing eastward
through the evening. Rough timing estimates with hi-res model
guidance puts storms in the James River Valley by 8-10 PM CDT and
out of the forecast area shortly after midnight. All severe weather
hazards remain possible this evening, including wind gusts of
75+ mph, large hail of 2"+, and tornadoes. A more technical and
in-depth analysis of storms and possible hazards will be out
with the afternoon discussion and forecast package.

UPDATE Issued at 625 AM CDT Tue Jun 9 2026

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

&&

.DISCUSSION...
Issued at 213 AM CDT Tue Jun 9 2026

The main highlight will be the severe storms expected this afternoon
through tonight with all modes of severe weather possible. Setting
the stage, a slightly negative tilted trough continues over the
western CONUS with the entire Northern Plains on the PVA side of
this trough in southwesterly flow. By this evening an area of
embedded higher winds of 45 to 60kts will overspread the western to
central Dakotas by this evening, highest over ND. Down at 850mb, a
LLJ will be in place on the downstream side of the trough with
speeds of 20-45kts this afternoon, highest in ND and southward
through north central SD. As the evening into the night progresses,
this LLJ will track east and strengthen (45-55kts). Its low pressure
by 18Z is forecast to be along the ND/MT border and its warm front
eastward across ND and cold front (and surface trough ahead of it)
southward along the SD/WY border leaving the entire CWA within the
warm sector as strong return flow at surface to 850mb will allow
temps to reach the 90s (upper 90s over south central SD). NBM is
highest on temps compared to CAMS so lower confidence if we can
reach these highs as dp`s will be higher. Moist dewpoints will be in
the mid to upper 60s and topping out at +16/C at 850mb! Add in
SB/ML/MU CAPE of 3000-4000j/kg, with HREF max between 4-5K+j/kg
and we have lots of energy! This "should" all work together and
break the cap later on this afternoon where storms will be able
to develop and intensity rather quickly with bulk shear of
30-40kts. By 00Z, the low will track a bit northeast and cold
front extending southward over or just west of central SD. The
only thing that could put a kibosh in this entire setup is that
we are too capped aka temps at 700mb are too warm and nothing
happens. Right now temps range from 10-12C per HREF/REFS by peak
heating so should be able to break it.

HREF composite Z>40 dbz paintballs show discrete cells/clusters
developing over central SD (or moving in from western SD), around
~22-00Z. UH 2-5km >150m2s2 (indicating supercells) shows this threat
over central SD (possibly further east) with the highest
probability along the ND/SD border. This will be short lived as
through the evening, reflectivity paintballs indicate these
cells merging (with additional convection) and forming a line
(potentially consisting of embedded supercells at first). As the
storms continue to grow upscale and mature (cold pool develops)
then it would become more of a wind threat/MCS as it progresses
eastward with help from the LLJ/shear. As of now it should be
out of eastern SD/western MN by ~06-08Z with ongoing stratiform
rain behind it. Low confidence on the discrete to linear timing
as some models show this linear setup occurring as it enters our
western CWA while some keep a discrete setup turning linear
over central SD.

As mentioned, supercell threat will be highest this afternoon/early
evening. Any supercells that do form will have this bulk shear,
0-3SRH of 100-200 m2s2, and mid level lapse rates of 7-8C/km.
Large hail will be likely with diameters of at least 2 inches as
SHIP values are 2 and above. Supercells will also have an
environment conducive for tornadoes but only for a few hours
indicated by curved hodographs with the best right curvature
between 23-04Z over north central to northeastern SD along the
ND border per RAP with 0-1 SRH of 100-250m2s2, 0-1 shear of
15-20kts increasing to around 20-30kts or so by 02Z, and STP of
1-2. Only caveat is that LCL`s seem to run about 1000m or
higher per RAP which if produced a tornado, would be high based.
Beyond this as the storm mode turns linear the tornado threat
should diminish (unless we hang onto embedded supercells
longer as it tracks east) becoming a high wind threat (with the
help of the increasing LLJ) with gusts of 75+ mph as DCAPE will
be over 1000j/kg, especially with any bowing segments if a RIJ
forms. If one does form then there is a threat of mesovortices
within the balanced/shear dominant part of a line (north of bow)
and only if a cold pool forms along with 0-3km line normal shear
of at least 30kts. This will not be determined until closer or
as the event is evolving.

So to put it all together, the SPC continues with an Enhanced risk,
level 3/5, covering the entire CWA with a 5% tornado risk (Cig1)
meaning max intensity of EF2+ possible. Cig 1 intensity covers
the entire CWA for hail (2"+ diameter) with the highest
probability between the Missouri and James River (where
supercells are possible). Lastly wind gusts of 75mph+ is
possible for the entire CWA(Cig1). With PWATs over an inch,
heavy rain and the risk of flooding or flash flooding is also
possible.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1220 PM CDT Tue Jun 9 2026

Terminals KABR,KATY,KPIR,KMBG

The main aviation concern today will be a line of storms, possibly
severe, to move through the forecast area. Storms are expected to
develop over central South Dakota (west of the Missouri River) late
this afternoon before progressing eastward through the evening and
departing the forecast area to the east by around 05Z this evening.
These storms will bring severe winds, perhaps to 65 knots or greater
at times. Large hail and tornado development will also be a threat
with these storms. Storms may also bring MVFR ceilings, and heavy
downpours will also have the potential to bring visibility down to
MVFR to IFR levels at times. Outside of these storms, expect VFR
conditions through the TAF period.

&&

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

&&

$$

UPDATE...BC
DISCUSSION...MMM
AVIATION...BC