992
FXUS63 KFSD 021128
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
628 AM CDT Sat Aug 2 2025

.KEY MESSAGES...

- Areas of smoke will continue to cause impact visibility and
  air quality at times through the weekend.

- Periodic chances for showers and thunderstorm expand east
  tonight and Sunday, then continue through early next week.
  Severe weather chances are low this weekend, with isolated
  strong to severe storms possible Monday.

- Below normal temperatures continue through early next week.
  Warmer air and increasing humidity return mid-late week.

- Unsettled pattern continues mid-late week. Could see a
  greater severe threat at times from Tuesday night, but
  confidence in storm chances is low from Wednesday onward.

&&

.DISCUSSION...
Issued at 342 AM CDT Sat Aug 2 2025

TODAY-SUNDAY: Weak MCV over north central SD early this morning
with weakening showers/storms trying to swing into our western
counties. Could see spotty showers/isolated storms generally
west of a Huron-Lake Andes line through mid morning, but this
activity should diminish as the MCV lifts northeast into North
Dakota.

Expect dry conditions to dominate the late morning-afternoon,
but a trailing wave could trigger additional showers/storms in
central South Dakota this evening. Seeing decent agreement in
high-res models in this activity increasing in coverage as the
wave slides across southeast South Dakota later tonight into
Sunday morning, aided by low level warm advection and a modest
low level jet. With weak mid-level lapse rates & little shear,
severe weather is not expected. However, may have to watch for
pockets of heavy rain as HREF LPMM precipitation indicates a
potential for localized 1-2+" amounts late tonight/early Sunday
between the James River Valley and I-29.

Later Sunday is a little more uncertain regarding placement and
exact timing of rain chances, but with the mid-upper level
trough lingering over eastern North Dakota, any subtle waves
swinging through the base of the trough could keep scattered
showers/storms in play through the afternoon and overnight. At
this time, the severe weather threat remains low during this
period.

Temperatures look to remain 5-10F below normal for early August
with highs mostly in the 70s this weekend.

MONDAY-TUESDAY NIGHT: The stagnant upper trough in eastern
North Dakota begins to lift northeast Monday as an upper ridge
begins to build eastward into the Plains. Though still slightly
below normal, temperatures begin an upward swing and southerly
flow will support increasing low level humidity. As a result,
will see greater instability by Monday afternoon, with some
uptick in deep layer shear in response to stronger mid-upper
level winds ahead of the building ridge. Thus cannot rule out a
few pulsy strong to severe storms, with isolated large hail and
damaging winds as the primary threats.

A stronger mid-level wave looks to swing east across the Dakotas
and Nebraska Tuesday-Tuesday night, resulting in 30-40kt of deep
layer shear. This coupled with steepening mid level lapse rates
could support some strong-severe storms Tuesday afternoon and
evening, though timing and location are still uncertain.

WEDNESDAY-FRIDAY: Mid-late week looks to remain unsettled over
the northern Plains as various waves traverse through moderate
west-southwest flow in the mid-upper levels. Difficult to
pinpoint favored location/timing of storm chances, and it is
possible the greater chances may be focused just north of our
forecast area with the upper level jet closer to the Canadian
border.

Warmer and more humid air does return through this period with
highs pushing back into the 80s to mid 90s. While this will
lead to greater instability with steep mid-level lapse rates,
forecast soundings also show a fairly stout capping inversion.
Would likely take a stronger wave/boundary to break through the
cap and NBM pops reflect this with sub-30% chances for most
locations south of Highway 14 through this period.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 628 AM CDT Sat Aug 2 2025

Showers and a few thunderstorms west of US Highway 81 at the
start of the period should weaken through 17Z, but could impact
KHON with brief MVFR visibility. Additional showers and storms
develop across central and eastern South Dakota during the late
afternoon and evening, working across the I-29 corridor and into
portions of southwest MN/northwest IA late in this TAF period.
Occasional MVFR-locally IFR visibility will be possible with
this activity which could contain brief heavy downpours.

Aside from any showers/storms, occasional MVFR visibility in
FU from Canadian wildfires will continue to impact the forecast
area at times through this TAF period and beyond into the day
Sunday.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...JH