122
FXUS63 KFSD 262328
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
628 PM CDT Fri Jul 26 2024

.KEY MESSAGES...

- Hot and humid conditions will continue through next week.
  Daily afternoon temperatures in the upper 80s and 90s with dew
  points in the low 70s will result in late afternoon heat index
  values in the mid 90s to near 100 degrees.

- Wildfire smoke will remain over the area through at least
  early Saturday. Surface impacts will be minimal, but Air
  Quality is in the Moderate category this afternoon. Those who
  are highly sensitive to air pollution may be impacted.

- Low chances (<20%) for showers and thunderstorms Sunday
  morning and early afternoon. Sunday evening chances increase
  (35-55%) for scattered thunderstorms. There is potential some
  storms could become strong to severe, mostly during the
  overnight hours.

&&

.DISCUSSION...
Issued at 140 PM CDT Fri Jul 26 2024

Afternoon skies continue to be obscured by wildfire smoke. While
most of the smoke has remained aloft, air quality due to PM2.5 at
the surface has remained in the Moderate category (level 2 of 6).
While this will not impact most, very sensitive populations may need
to restrict their time outdoors.

Winds this afternoon and into the evening will be breezy out of the
south. Gusts 20-25 mph will continue through midnight, calming
slightly toward Saturday morning. Lows tonight will be on the warm
side of average in the low 70s. Chances for fog overnight are low
(<15%), and if any does form it will be patchy in nature. Areas most
likely to see fog or low stratus development is east of I-29.
Winds will increase again and become south-southwesterly as the SPG
tightens in the afternoon. This will bring in slightly drier air and
so conditions will be slightly less humid than Friday. Strong WAA
will still result in hot afternoon highs in the upper 80s east of I-
29, and low 90s west. Aloft, flow becomes northwesterly and begins
to push wildfire smoke out of the area.

Conditions for Sunday will be hot and humid with highs again in the
mid 80s east of I-29, and low 90s west. Dew points will be in the
60s to low 70s. A series of weak mid-level waves Sunday brings
periodic low chances (<20%) chances for isolated to scattered and
thunderstorms during the morning and early afternoon. These
storms should remain sub-severe, but could produce a few
stronger wind gusts. Sunday evening a stronger wave could
trigger additional thunderstorms with the potential that a few
could become strong to severe. High instability and steep mid-
level lapse rates will be in place over a large portion of the
region, but so will a strong capping inversion. The best forcing
looks to remain to our north, so there is a question as to
whether or not the cap can be broken. Currently, the best chance
for stronger storms looks to be overnight when the LLJ picks up
and a band of 850 mb vorticity pushes in from the west. Lows
for Sunday night will be slightly cooler thanks to the
northwesterly winds behind the cold front, in the mid to upper
60s.

CAA results in slightly cooler day for Monday, with highs in the mid
to upper 80s. Dew points will still be high, though, in the 60s and
70s. By Tuesday morning, winds will again be out of the south, and
WAA will increase, as will the flow of moist air into the region
from the south. Hot and muggy will be the story for the first half
of the week. In addition there will be periodic chances for showers
and thunderstorms as a series of weak disturbances move through the
mid-levels. By the end of the week another high pressure ridge looks
to begin building in.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 628 PM CDT Fri Jul 26 2024

VFR conditions will be the rule at TAF airfields through 28.00Z.
Lingering isolated CU early this evening will quickly dissipate
within the next couple hours with mostly clear/sunny skies
continuing through the remainder of the period given relatively
dry atmospheric column.

Southerly surface winds will remain breezy this evening and
overnight with occasional gusts up to 22 kts at KHON/KFSD,
whereas winds will weaken a bit and turn to the southeast at
KSUX. Winds Saturday will once again be from the south with
gusts to 25 kts at all TAF airfields.

Stronger winds aloft overnight will allow for some low-level
wind shear concerns at KHON/KFSD. Expect winds in the 1500 to
2500 kft layer to increase to between 40 and 45 kts before
diminishing after sunrise Saturday morning.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...Rogers