Tornado and Hail in South Dakota, August 22, 2021

Area Forecast Discussion
National Weather Service Aberdeen SD
1254 PM CDT Sun Aug 22 2021

.UPDATE...
Issued at 1254 PM CDT Sun Aug 22 2021

18z aviation discussion updated below.

UPDATE Issued at 1023 AM CDT Sun Aug 22 2021

Current area of showers and storms in central sd this morning
lifting quickly off to the northeast. The radar returns have
weakened some along with decreasing lightning activity. It is
moving into less instability to the northeast. Expect this area to
continue to lift northeast, weaken, and move out of the region
into the early afternoon. Otherwise, the sun will come out and
warm it up and destabilize it. With this destabilization along
with steeper mid level lapse rates up to 8C and good deep layer
shear, some severe storms will be more likely with this second
round of storms. Made adjustments to the weather and pops through
this evening along with increasing the winds.

&&

.SHORT TERM...(Today through Monday Afternoon)
Issued at 400 AM CDT Sun Aug 22 2021

The first round of waa induced showers has begun this morning as
southeasterly sfc winds increase across central SD ahead of an
approaching sfc low and upper trough. Helping to feed the waa and
moisture availability is a 45 kt llj that will only gradually
diminish to 30 to 35 kts as it pushes east this afternoon ahead of
the sfc low. With daytime heating and the interaction of the upper
trough and the llj late this afternoon into the evening from the
James Valley east, there will be the potential for some strong to
severe storms. There are a couple of limiting factors, however.
Dewpoints in the 40s and 50s will be slow to rise into the 60s to
provide enough instability. Dry, warm air will quickly push in from
the west behind the low helping to set up a cap. Seeing any
redevelopment in the upper trough interaction is more unlikely the
farther west you go. LLM may not build over the far east as quickly
as models depict, either. The sweet spot may be right over the James
Valley between 20z and 0z with strong shear, better moisture
channeling up the valley and the right alignment of the shortwave
trough as it catches up with and surpasses the sfc front. All
hazards will be possible if any supercells manage to form along this
boundary.

The other concern of the day is the dry air mass behind the low.
Areas west river will see RH fall to around 20 percent with some
breezy winds still in place in the upper trough until closer to 0z.
Jones and Stanley counties could near red flag conditions,
especially if they miss out on wetting rain this morning. Due to
uncertainty with placement of morning convection, however, opted to
forgo a headline. Hot and dry conditions on Monday will lead to low
RH again, but winds will be more on the marginal side for red flag
if still breezy.

.LONG TERM...(Monday Evening through Saturday)
Issued at 400 AM CDT Sun Aug 22 2021

Not really much change for the extended with closer to seasonal
temperatures, with the upper pattern dominated by a mostly zonal
southwest oriented flow. A plume of mid level moisture from the
Desert Southwest, and a warm advection push ahead of a very subtle
wave will bring chances for moisture, though with 700mb temperatures
around +13C this will be confined to elevated convection. Despite
some cooling aloft, and a surface front (though there is some
difference between deterministic guidance on timing) BUFKIT profiles
never really suggest convection will become rooted in the boundary
layer. We should have a mostly dry Tuesday night and while blended
guidance has chance POPs for Wednesday, there is a shortwave ridge
over the western Dakotas, so again probably confined to weak
elevated convection. An upper trough deepens over the western CONUS
for a stronger mid level southwesterly flow regime. There are 3
distinct waves that follow which is why the later half of the work
week and into the weekend looks to be more active.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1254 PM CDT Sun Aug 22 2021

Terminals KABR,KATY,KPIR,KMBG

Showers and storms are expected to affect the ABR and ATY airports
at or in the vicinity early this afternoon before more showers and
storms develop later this afternoon and evening. This second round
of showers/storms could again affect ABR and ATY as the responsible
upper level lift and surface trough moves/pushes east. Otherwise,
gusty winds from the south southwest at 15 to 30 knots will become
west northwest into the early evening and then become light tonight.
With the recent rainfall, light winds, and clear skies tonight
expect some MVFR fog to form at both ABR and ATY with possible lower
IFR vsbys at times.

&&

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

UPDATE...Mohr
SHORT TERM...Wise
LONG TERM...Connelly
AVIATION...Mohr

Hazardous Weather Outlook
National Weather Service Aberdeen SD
337 AM CDT Sun Aug 22 2021

MNZ039-046-SDZ004>011-016>023-037-051-230845-
Traverse-Big Stone-Campbell-McPherson-Brown-Marshall-Roberts-
Walworth-Edmunds-Day-Potter-Faulk-Spink-Clark-Codington-Grant-Hamlin-
Deuel-Hand-Buffalo-
337 AM CDT Sun Aug 22 2021

This Hazardous Weather Outlook is for west central Minnesota,
central South Dakota, north central South Dakota and northeast
South Dakota.

.DAY ONE...Today and tonight.

Showers and thunderstorms will move through the region today. Some of
these may be strong to severe.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

SDZ003-015-033>036-045-048-230845-
Corson-Dewey-Stanley-Sully-Hughes-Hyde-Jones-Lyman-
337 AM CDT Sun Aug 22 2021 /237 AM MDT Sun Aug 22 2021/

This Hazardous Weather Outlook is for central South Dakota and
north central South Dakota.

.DAY ONE...Today and tonight.

Showers and thunderstorms will move through the region today. Some of
these may be strong to severe. As winds increase, areas that do not
receive wetting rains in the thunderstorms will see fire danger rise
to very high this afternoon.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Special Weather Statement
National Weather Service Aberdeen SD
802 AM CDT Sun Aug 22 2021

SDZ033-045-048-221345-
Stanley SD-Lyman SD-Jones SD-
802 AM CDT Sun Aug 22 2021

...A strong thunderstorm will impact portions of northern Jones,
south central Stanley and northwestern Lyman Counties through 845 AM
CDT/745 AM MDT/...

At 801 AM CDT/701 AM MDT/, Doppler radar was tracking a strong
thunderstorm near Okaton, or 10 miles northwest of Murdo, moving
northeast at 40 mph.

HAZARD...Wind gusts up to 50 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Van Metre around 815 AM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Aberdeen.

&&

LAT...LON 4399 10106 4400 10105 4402 10105 4438 10059
      4400 10024 4384 10095
TIME...MOT...LOC 1301Z 236DEG 37KT 4398 10089

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

Vipond