732
FXUS63 KFSD 111746
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1246 PM CDT Mon Aug 11 2025

.KEY MESSAGES...

- Areas of smoke, surface and aloft, will create hazy skies with
  occasional impacts to air quality through early Tuesday. Minor
  visibility reductions are also possible at times.

- Wednesday night into Thursday morning may bring a few
  thunderstorms to areas north of I-90, with the better chance
  closer to highway 14. Severe weather risks are low.

- Thursday into Saturday will see increased temperatures and dew
  points return, with Moderate/locally Major Heat Risk. Highs in
  the upper 80s to mid 90s and dew points in the 70s may result
  in 100+ degree heat indices for some locations.

- Although uncertainty remains in details, thunderstorm chances
  return late week into this weekend. Pattern favors nighttime
  to early morning thunderstorms, with locally heavy rain and
  perhaps some severe storms possible.

&&

.DISCUSSION...
Issued at 408 AM CDT Mon Aug 11 2025

TODAY-TUESDAY: Main concern early this week will be another
round of wildfire smoke which has filtered into the northern
Plains from Canada. Latest HRRR/RRFS projections hang onto areas
of smoke both aloft and at the surface through today, slowly
exiting east tonight through Tuesday morning as a weak cool
front pushes through the forecast area. Aside from shallow fog
which is also reducing visibility early this morning, expect
area visibility reports in the 3-5 mile range are generally from
the surface smoke with air quality readings largely in the
yellow to orange range (Moderate to Unhealthy for Sensitive
Groups) as of 3 am. However, upstream air quality observations
in central-northeast SD/western ND are in the red (Unhealthy)
category, and will have to watch for worsening air quality and
perhaps visibility as we move through the morning.

Other than the smoke, today and Tuesday look to be relatively
nice days with modest humidity levels for this time of year and
temperatures near to slightly below normal. A subtle wave may
produce some sprinkles north of I-90 late this afternoon/evening
but most areas should remain dry.

WEDNESDAY-THURSDAY: Rising heights aloft and increasing south
winds in the low levels will allow warmer air to slowly build
into the region midweek. Still seasonal high temperatures in the
80s Wednesday will warm into the mid 80s to mid 90s by Thursday,
accompanied by some increase in low level humidity as well. The
combination of warmer temperatures and higher dew points may
push heat indices above 100F in some areas Thursday afternoon,
so will have to monitor trends for possible heat headlines.

Placement of the mid-level thermal ridge should keep rain chances
largely north of the area, though a modest wave seen in several
model solutions could brush our northern counties with some
storms Wednesday night into early Thursday. At this time, the
greater risk for a few strong-severe storms looks to remain
north of our forecast area, but if the wave tracks a bit farther
south we will have to monitor potential into the Highway 14
corridor Wednesday night.

FRIDAY-SUNDAY: The heat peaks Friday, with a transition to
southwest flow aloft potentially bringing us back into a more
active pattern by Friday night into the weekend. Seasonably
warm temperatures and abundant low level humidity will fuel
ample instability, but similar to this past weekend, mid level
temperatures may be too warm to allow convective development in
our area during peak heating. Instead, could more likely see
development to our west move east into our forecast area during
the nighttime to early morning hours. Still several days away,
so details regarding storm location and severe potential are
uncertain. However, ensembles show precipitable water values
increasing above the 90th percentile of climatology with a
potential southerly low level jet through eastern Nebraska,
which could support at least a locally heavy rain threat.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1246 PM CDT Mon Aug 11 2025

Outside of a stubborn IFR/MVFR stratus at KSUX that should burn
off/lift with afternoon heating, expect VFR conditions at TAF
airfields through the period. For KFSD/KSUX, there may be
reductions in visibility down to 6SM due to lingering wildfire
smoke through the afternoon/early evening. Conditions will
improve later tonight.

Winds through the period will be light, initially from the
southwest, then turning to the northwest from west to east late
tonight into Tuesday morning.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...Rogers