499
FXUS63 KFSD 061749
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1249 PM CDT Sun Sep 6 2026

.KEY MESSAGES...

- Isolated strong to severe storms remain possible into the
  late afternoon hours. Brief downburst winds of 50 to 60 mph
  will be possible over NW Iowa and adjacent SD/NE counties.

- Heavy rain will be the primary risk into the evening with
  rainfall rates of 1-3" per hour and local totals of 3-5"
  possible. A flood watch for flash flooding continues into late
  evening.

- Isolated strong to severe storms will again be possible late
  Monday afternoon into Tuesday morning. These risks may
  continue into NW Iowa Tuesday afternoon.

- Quiet but continued warm conditions are expected for the rest
  of the work week.

&&

.DISCUSSION...
Issued at 1246 PM CDT Sun Sep 6 2026

THIS AFTERNOON: Strong convection continues to develop in areas
along but mostly east of I-29 this afternoon.  The area continues to
reside in a moderately unstable environment, but lacks any
meaningful shear and mid-lvl lapse rates.  However, climatologically
significant PWATs are in place, with enough DCAPE to suggest an
increased risk for wet microbursts over the next 1-3 hours in a
narrow corridor from Madison to Sioux Falls, Sioux Center, Cherokee,
Storm Lake, Le Mars, and Sioux City. Rainfall may be the most
impactful hazard this afternoon with 1-2 hr totals of 3-4" already
in portions of southern Minnesota.  Additional convection is likely
to continue to produce 2-4" totals in pockets of NW Iowa, though
cold pool development may help push storms off an area before
extreme values may be produced.  The stronger MCV will also nudge
it`s way northward later this afternoon, and may work to produce
additional northward/northeastward convection with it.

TONIGHT: This shortwave/MCV will drag it`s feet eastward this
evening, with some expected weakening of convection with the lost of
daytime heating and general stabilization of the environment nearby.
However, an increased LLJ may begin to develop after 02Z which
could bring returning elevated showers and isolated
thunderstorms to the CWA late this evening and continuing into
the overnight hours. This activity will likely not be severe,
but any shower could still bring brief heavy rain.

MONDAY-TUESDAY: Elevated shower activity diminishes towards daybreak
as shortwave ridging arrives. An ejecting trough out of the Rockies
will bring additional elevated convection into central and northern
South Dakota into Monday afternoon, perhaps grazing the western CWA.
As the EML gradually erodes into south central SD late in the
afternoon, a few strong to severe storms may develop and track
east southeast into the early overnight hours. As the LLJ
increases after dark, elevated convection may expand in coverage
with continued low- end severe weather risks for Tuesday
morning.

More uncertainty for Tuesday, which is focused moreso on the
location of the surface front and impacts of overnight elevated
convection.  While the primary surface front settles in northwest
Iowa, a secondary stronger dew point gradient arrives later in the
afternoon. Should sufficient clearing develop, then a storm or two
could become stronger by mid-afternoon with activity quickly
tracking southeast by the evening.

EXTENDED: With ongoing convection, no forecast changes made to the
extended as a temporarily reprieve from active weather
develops. Temperatures may still remain near to above normal
for the rest of the work week.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1219 PM CDT Sun Sep 6 2026

Scattered convection will continue to develop early this
afternoon, and continue into early evening. In thunderstorms,
brief 40 to 60 mph wind will be possible, along with small hail,
and torrential rainfall. The coverage near the TAF sites
remains fairly uncertain, and impacts may be brief if they take
place.

Scattered showers and isolated thunderstorms continue south of
I-90 into the evening and early overnight hours. Again, brief
reduction to MVFR or IFR conditions are possible, but will be
driving by any sporadic updraft that passes through. Coverage in
SUX high enough to include prevailing wording ATTM.

VFR conditions may fall to MVFR levels into Monday morning,
though significant uncertainty remains as far as any stratus
development.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Flood Watch until 10 PM CDT this evening for SDZ062-067-071.
MN...Flood Watch until 10 PM CDT this evening for MNZ080-081-089-
     090-097-098.
IA...Flood Watch until 10 PM CDT this evening for IAZ001>003-
     012>014-020>022-031-032.
NE...None.

&&

$$

DISCUSSION...Dux
AVIATION...Dux