392
FXUS63 KFSD 301737
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1237 PM CDT Sat Aug 30 2025

.KEY MESSAGES...

- An unsettled pattern will prevail through the holiday weekend,
  with highest rain chances toward the Missouri River Valley.
  The greater risk of heavy rainfall has shifted into Nebraska,
  but still a low-moderate (20-40%) chance of exceeding 1 inch
  near/southwest of the Missouri River in south-central SD.

- Drier conditions will be more dominant along and northeast of
  a line from Huron-Sioux Falls-Storm Lake, though scattered
  afternoon/evening showers are possible today through Monday.

- Severe weather risks are low, but non-zero risks for a few
  weak funnel clouds with developing "popcorn" showers during
  the afternoon-early evening hours.

- Chance of showers/storms lingers into Tuesday-Tuesday night.
  Some uncertainty in details, but the severe weather risk looks
  to remain low at this time.

- Brief shot of colder air pushes into parts of the northern
  Plains/Upper Midwest mid-late next week.

&&

.DISCUSSION...
Issued at 355 AM CDT Sat Aug 30 2025

TODAY-SUNDAY: A slow moving mid-upper level low will meander
southeast from western SD early this morning, into eastern
Nebraska by late Sunday. While we have not yet reached the
start of meteorological Autumn, this system may act more like a
weak winter system with rainfall, at least in part, focused by
weak mid-level frontogenesis just northeast of the low track,
aided by weak warm advection east of an inverted trough.

The latest models appear to have shifted the track of the low a
bit to the southwest and south compared to this time yesterday,
which slides the aforementioned weak forcing and potential for
more persistent moderate or even heavy rainfall to our west and
south. While some locally heavy rains may brush areas near and
southwest of the Missouri River Valley west of Yankton, overall
forecast rainfall amounts have dropped sharply for the southwest
portions of the forecast area. Deterministic QPF now less than
an inch over the next 72 hours, though HREF does still indicate
low to moderate (20-40%) probabilities for 24-hour amounts in
excess of 1 inch for the above-mentioned Missouri River locales
through tonight. As such, will still have to monitor these areas
for locally heavy rainfall.

Farther to the northeast, deep moisture will be harder to come
by thanks to a dry east-southeast low-mid level flow around a
prominent ridge across the northeast half of Minnesota. While
this will keep the northeast half of our forecast area on the
drier side through this holiday weekend, do not expect it to be
completely rain-free. Models suggest 500-1000 J/kg of MLCAPE is
possible by peak afternoon heating, which could support isolated
to scattered popcorn showers and perhaps a few thunderstorms.
With meager deep layer shear, severe weather is not a concern.
However, latest RAP continues to suggest a ribbon of enhanced
stretching potential which could support a few weak funnel
clouds during the developing stage of these showers.

Highs through Sunday should be mostly in the 70s, but some areas
toward the Missouri River Valley may hold in the 60s if rain is
more prevalent.

LABOR DAY-TUESDAY NIGHT: The mid-upper low continues to slowly
wobble southeastward Labor Day through Monday night, which will
keep moderate (40-50%) rain chances over much of the area for
the Labor Day holiday. Lesser chances for showers linger Monday
night, but as the weekend system slides farther southeast, our
attention then turns to the northwest and an approaching trough
for Tuesday-Tuesday night. Models are still having difficulty
agreeing on the timing/strength of this trough and associated
cold front, so rain chances are currently lower in confidence.
Shear generally remains less than 30kt until the late evening
to overnight hours with an approaching upper level jet, so it
seems our severe weather risks will remain on the low side.

WEDNESDAY ONWARD: A sharp cold front drops through the northern
Plains/Upper Midwest Wednesday as the trough strengthens into a
closed mid-upper level low over the western Great Lakes. Still
seeing discrepancy with the track of the coldest temperatures,
with at least a low (20-30%) probability of highs remaining in
the 50s across portions of southwest Minnesota/east central
South Dakota on Wednesday/Thursday.

Perhaps more noteworthy is a low-moderate (30-40%) probability
that low temperatures over the Coteau in east central South
Dakota, and portions of southeast Minnesota/northwest Iowa,
could fall below 40F Wednesday night/early Thursday. The NBM
10th percentile does show some areas with lows in the mid 30s,
so while it`s far from the most likely scenario, a light frost
is not out of the question if colder model solutions pan out.

The cold push will be short-lived though, with mild air
returning by week`s end.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1237 PM CDT Sat Aug 30 2025

Low level stratus continues to sit over parts of southwest Minnesota
early this afternoon at IFR/LIFR levels. Should see this stratus
continue to slowly lift through the rest of the afternoon hours.
Light to moderate rain showers persist across parts of the Missouri
River in south central South Dakota along with ceilings down to MVFR
thresholds. Should see rain and associated MVFR ceilings persist in
this area for a large part of the TAF period as showers become more
widespread this evening. Confidence is only high enough at this time
to put prevailing rain in KSUX`s TAF. There could also be a few
rumbles of thunder but confidence is not high enough to include in
at TAFs at this time. Ceilings look to slowly lower overnight to
MVFR levels tonight and last through the rest of the TAF period.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...Meyers