466
FXUS63 KFSD 021904
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
204 PM CDT Sat Aug 2 2025

.KEY MESSAGES...

- Surface and vertical smoke layers will gradually move
  eastward over the upcoming 18 hours. Air quality is likely to
  improve Sunday morning in most areas.

- Occasional shower and thunderstorm risks continue through the
  weekend, with primary focus overnight into Sunday. Small hail
  could be possible, along with locally heavy rainfall totals.

- More conditional risks of strong to severe storms develop
  Monday afternoon and evening. Large hail and downburst winds
  the primary risks.

- Temperatures begin to warm above normal through most of next
  week, with persistent unsettled weather. Strong to severe
  storm risks increase by Tuesday and may continue through
  Thursday.

&&

.DISCUSSION...
Issued at 202 PM CDT Sat Aug 2 2025

THIS AFTERNOON:  A slowly developing upper trough over the Dakotas
will continue to provide a significant influence on the weather in
the local area over the upcoming 36 hours.  This afternoon, we`re
continuing to see increased cloud cover and lingering showers
as an initial lobe of vorticity moved east through the Tri-
State area. For the rest of the afternoon, we`ll have to pay
some attention to central SD where low-lvl return flow is
focused and weak mid-lvl dPVA continues. While soundings show a
bit of low- lvl inhibition, I would not be surprised to see a
few isolated non-severe showers/thunderstorms into the evening.

TONIGHT:  Greater precipitation chances are expected to develop
overnight as another lobe of vorticity pivots into central and
easterly South Dakotas. Increasing mid-lvl lift along with
increasing low-lvl convergence as the LLJ increases should lead to
scattered to numerous shower and thunderstorm development along and
east of the James River valley after midnight and into Sunday
morning.  Soundings support only minimal small hail risks, but with
PWAT values nearly 130% of normal and generally slow storm movement
localized heavy rain is possible.  While the HREF mean suggests 0.5-
1" totals, the HREF 6-hr PMM guidance suggests highly localized
pockets of 1-3" of of rain, especially along the SW-
-->NE oriented LLJ axis.  The more persistent westerly flow will
also begin to scour surface and elevated smoke eastward, with
rapidly improving air quality expected into Sunday.

SUNDAY:  Showers and thunderstorms slowly weaken Sunday morning and
shift eastward into MN/IA.  For most of the day, quiet weather is
expected with a southerly wind. We`ll have to keep an eye once again
towards central SD along a stationary boundary that becomes
established from the Nebraska Panhandle northeast into the far
northeastern portions of South Dakota. There remains considerable
uncertainty on any potential mid-lvl vorticity tracking southeast in
the afternoon which could help initiate a few late day thunderstorms
that would then track southeast in the evening.  Shear remains quite
weak, and with upwards of 1500 J/KG MLCAPE, overall severe weather
risks remain low if storms develop.

MONDAY:  Any overnight convection gradually weakens with the loss of
diurnal heating, however with persistent low-lvl warm advection,
showers could linger into Monday morning.  Mid-lvl heights begin to
build on Monday, and there is strong evidence of an EML moving
northeast into the area during the day.  While a great deal of
instability is likely to build (especially along and west of the
James River), soundings continue to show general inhibition through
the afternoon and evening.  The end result may be only isolated
stronger storms trying to develop.

TUESDAY-FRIDAY: A persistent feature this Summer has been a broad
but flattened mid-lvl ridge throughout the CONUS. This pattern will
once again returns for much of next week, signaling a return of
warmer than normal temperatures and periodic risks for strong to
severe convection.  As far as temperatures are concerned, 850 mb
temperature anomalies begin to approach 3-8 degrees above normal and
support temperatures back into the upper 80s to 90s.  Timing of
subtle shortwaves remains more difficult, but there is some focus
around Tuesday and again Thursday. AI learning models along with
CIPS analog based guidance support general increases in severe
weather potential through the middle of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1158 AM CDT Sat Aug 2 2025

VFR conditions continue though the afternoon and evening hours.
A few sprinkles may continue into SW MN and NW IA into early
afternoon. We`ll gradually see an increase in diurnal based CU
this afternoon, with a very low risk for evening thunderstorm
development in central South Dakota. Occasional visibility
restriction due to smoke may linger into the early overnight.

Higher rain chances develop after midnight west of I-29, with
this activity moving east slowly into Sunday morning.

MVFR ceilings may try to develop at times Sunday morning as
winds remain southwest.

&&

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

&&

$$

DISCUSSION...Dux
AVIATION...Dux