346
FXUS63 KFSD 112010
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
310 PM CDT Fri Jul 11 2025

.KEY MESSAGES...

- A low end (level 1 of 5) risk of severe storms develops by
  late this afternoon, as a cold front brings scattered
  thunderstorms southward into the region. The main threats with
  the strongest storms will be up to quarter sized hail, strong
  winds up to 60 mph, and heavy downpours. An isolated funnel
  cloud or landspout is possible, mainly along the cold front
  itself.

- Temperatures cool Saturday, but heat and humidity build back in
  for Sunday through Tuesday. Cooler temperatures return for
  the middle and end of next week.

- Thunderstorm risks return for Sunday through Tuesday, with
  some threat of severe storms possible.

&&

.DISCUSSION...
Issued at 309 PM CDT Fri Jul 11 2025

A few showers and weak thunderstorm persist east of I-29 this
afternoon. Should see these showers and storms drift
east/southeastward over the next couple of hours. At the same time,
a cold front has pushed into the area from the northwest. This front
will serve as the focal point for new showers and thunderstorms to
develop on with convective initiation expected over the next 2 to 3
hours or so. Storms look to be initially discrete before some
upscale growth leads to a broken line/cluster of storms. CAPE value
will be sufficient at around 1,500 J/kg of instability but shear
will be quite weak on the order of 25 knots or less. That said,
still think an isolated chance for quarter size hail and damaging
winds to 60 mph is possible. The other aspect to the storms is the
potential for funnels or even a landspout. This potential is being
driven from the vorticity along the front itself. Despite the
fronts vorticity, LCL`s are decently high at around 4,000 to 5,000ft
so it may be a bit more difficult to any funnel to touch the ground.
Any chance for storms will come to an end by midnight as the showers
and storms push east of the area. Low temperatures will fall to the
upper 50s to low 60s.

High pressure will push into the Northern Plains on Saturday,
delivering dry and quiet conditions for the area. 850 mb
temperatures will warm to the teens aloft. Mixing these temperatures
to the surface will result in high temperatures in the upper 70s and
80s. Dew points will lower to the 60s to low 60s, which will keep
humidity values down to 30-60%, lowest west of the James River.
Thus, Saturday will be a nice day though there could be some
wildfire smoke both aloft and at the surface. Low temperatures will
fall to the upper 50s to low 60s overnight.

Sunday will be a hotter day as highs warm to the 80s to 90s, warmest
west of the James River. Southerly return flow on the backside of
the previously mentioned departing surface high. Dew points will
moisten to the 60s to even up to about 70F. This will increase
humidity values and also result in CAPE values up to 1,500 to 2,000
J/kg. Effective shear value will be sufficient on the order of about
30 knots but lift is questionable. A shortwave trough will reside
east of the forecast area, providing upper level subsidence across
the Northern Plains. However, a weak shortwave trough at 700 mb will
push into the area. A weak surface trough will push through the area
which could result in another chance for showers and thunderstorms.
This potential is quite uncertain though given the weak forcing that
is in place. As of now, the ensembles only show a low 10-30% chance
for rainfall amounts to exceed a tenth of an inch throughout the
day. Have left model blended PoPs at this time but trends will be
monitored.

Zonal flow sets up for the beginning of next week. This will promote
broad southerly flow into the Northern Plains, promoting humid
conditions across the area. High temperatures will remain near to
above average in the 80s and 90s. With weak shortwave troughs
passing through the upper level flow, chances for showers and
thunderstorms are possible. As of now, it looks like storm chances
will increase heading into Monday evening as forcing for ascent
strengthens. This chance for storms will persist through Tuesday as
a cold front passes through the forecast area throughout the day.
Given sufficient instability and enough shear in place, this could
lead to additional chances for showers and storms, some of which
could be strong to severe. Machine learning guidance also supports
this possibility as these models show about a 5-15% chance for
strong to severe storms. Will keep an eye on this potential over the
weekend.

Rain chances look to continue for Wednesday and Friday next week as
shortwave trough continue to track through the upper level flow.
Details of these waves is uncertain at this time so have left model
blended PoPs. In terms of temperatures, highs look to cool to near
to below average in the 70s to up to about 80F. Lows will fall to
the 50s and 60s overnight.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1239 PM CDT Fri Jul 11 2025

Mainly VFR conditions begin the TAF period. Light rain persists this
afternoon along and southeast of a KSLB to KSUX line and should
slowly push southeastwards over the next several hours. To the west,
a cold front has begun to push into the area, turning the winds at
the surface to out of the northwest in its wake. Some brief
reductions in visibility is being observed behind the front but
confidence is too low to include in a TAF at this time. Will keep an
eye on the lowered visibilities though.

Showers and thunderstorms are expected to develop along the front
later this afternoon. While storms look to develop along and east of
the James River, have decided to include a PROB30 group in KHONs TAF
for trailing light rain showers. Showers and storms will push
eastwards through the rest of the afternoon and evening hours before
sliding east of the area around midnight. This will leave clearing
skies and light northwest winds for the rest of the night and TAF
period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers