Yankton, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

104
FXUS63 KFSD 282019
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
319 PM CDT Sat Jun 28 2025

.KEY MESSAGES...

- Hot and humid conditions prevail this afternoon with heat
  indices into the 90s across the area.

- Two rounds of storms are possible tonight. The first round
  will come tonight, around 1 AM across portions of southwest
  Minnesota. These storms will be capable of large hail up to
  golf ball size and damaging winds to 60 mph.

- The second round of storms looks to push in from the west late
  tonight, around 4 AM, and persist into the morning hours
  tomorrow. Damaging winds to 70 mph and large hail up to half
  dollar size are the primary hazards.

- Storm risks continue into Sunday, though potential remains
  contingent on storm development this evening and night.

- Near to above normal temperatures for much of the upcoming
  week, with storm risks returning by the middle of the week.

&&

.DISCUSSION...
Issued at 318 PM CDT Sat Jun 28 2025

With morning showers and storms now mainly dissipated and well east
of the area, quiet conditions are in place. However, a boundary
draped from northeast South Dakota down through central and south
central South Dakota will set the stage for new thunderstorms to
develop on. Latest guidance is in unanimous agreement that storms
will develop along the boundary in parts of northeast South Dakota
and western Minnesota. Although, uncertainty increases in potential
convective develop along the central South Dakota portion of the
boundary. This is due to strong capping persisting across the
forecast area via a strong elevated mixed layer (EML) in place.
While there is decent vorticity and convergence along this portion
of the boundary, tough to say if storms will develop given the
strength of the cap. Especially since temperatures are a bit cooler
than previously forecasted. At the same time, the wave responsible
for the mornings storms is east of the area, promoting subsidence
across the region on its back side. Thus, think that storms will
develop during the evening hours in northeast South Dakota and
western Minnesota and drift southwards into portions of southwest
Minnesota by around 1 AM. Large buoyancy will be in place with CAPE
values exceeding 3,000 J/kg. However, the best shear will remain
north of the area while deep layer over southwest Minnesota remains
around 30 knots. Damaging winds to 60 mph and large hail up to golf
ball size will be the primary hazards. While convection could still
develop along the western portion of the boundary across central and
south central South Dakota late this afternoon and evening, think
that the large scale subsidence will most likely win out. Think that
convection has only about a 20% chance to develop on the boundary.
Have still let slight chance to chance PoPs along and west of the
James River for this evening in the low chance that storms do
develop.

Attention now turns to a second shortwave trough currently sitting
over southeastern Montana. This wave will drift eastwards through
the rest of today and looks to develop new convection along the
Black Hills this evening. With ample instability sitting across the
state of South Dakota, this next round of storms may grow upscale
into a mesoscale convective system (MCS) or a messy multicellular
system and track eastwards down I-90. While this round will be
better forced, only a few convective allowing models (CAMs) show
this potential but do think it is worth putting more weight into
this solution given the stronger forcing in place. The main
uncertainty regarding this scenario is that deep layer shear remains
modest at around 30 knots and instability wanes the more elevated
the system gets. However, like what we saw last night, the system
could become cold pool driven and then tap into the better
instability near or at the surface. Have increased PoPs up to about
50% for this potential tonight. While large hail up to half dollar
size is possible, damaging winds to 70 mph will be the primary
hazard with this system as it pushes into the area. Tornadoes are
not expected given how 0-3km shear is quite weak on the order of
only 10-15 knots. This system may last into the morning hours
tomorrow before it finally pushes east of the area.

Once the system is out of the area, Sunday looks to be a more quiet
day. This will again depend on the overnight storm development but
there is decent agreement amongst the hi-res guidance in the
previously mentioned boundary pushing out of the forecast area but
tomorrow afternoon. This should keep this highest chances for
convection southeast of the area, leaving mainly dry conditions in
place. With the wave coming through, Sunday will be a return to near
seasonable temperatures with warming to the 80s. Dew points will
remain in the 60s to 70, highest over northwest Iowa, so it will
still be a humid day. Low temperatures will fall to the 60s.

A strengthening shortwave trough aloft will be pushing through the
Upper Midwest on Monday, placing the backside over the Northern
Plains and thus keeping things dry via the subsidence from the wave.
Highs will be near normal in the 80s with lows falling to the
upper 50s.

Chances for rain could return for the middle and end of the week.
This looks to be driven by shortwave troughs passing through the
Northern Plains though considerable variance in these waves is
presented amongst medium range guidance. As such, have left model
blended PoPs in place. Aside from rain chances, the bulk of next
week looks to see high temperatures warming to the 80s and 90s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1244 PM CDT Sat Jun 28 2025

Morning showers and storms have weakened and pushed east of the
area. A few mid and high level clouds reside aloft but sunny skies
largely prevail. The morning storms produced an outflow boundary
that pushed into parts of southwest Minnesota, northwest Iowa, and
southeast South Dakota. A bit difficult to give an exact location
of this boundary as winds are recovering back to out of the
southeast. Otherwise, quiet conditions with southeast winds turning
more southerly with gusts up to 25 knots is expected for the
afternoon hours.

Showers and thunderstorms will develop across northeast South Dakota
and possibly back down to central South Dakota around 5 pm. The
storms look to track southeastwards and into KHONs area. These
storms look to persist through the evening hours before another
potential round of storms moves through during the overnight hours.
However, the evolution of convection is uncertain and can still
change so have left PROB30 groups to account for this uncertainty.

Winds will be turning to out of the north/northeast to end the TAF
period tomorrow morning.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers