773
FXUS63 KFSD 301849
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
149 PM CDT Fri Oct 30 2026

.KEY MESSAGES...

- Showers and very isolated thunderstorms are likely tonight
  into Saturday morning, mainly near and east of Highway 81.
  Drizzle and spotty showers will be possible west of Highway
  81. No severe weather expected.

- A more widespread rain returns later Sunday night into Monday
  night. The latest guidance suggests about a 60-90 percent
  chance for more than an inch of rain. Flooding is unlikely,
  but not zero. Additional rainfall is likely on Tuesday.

- A low confidence threat for low topped supercells Monday
  afternoon and evening in far southeast SD, northeast NE and
  northwest IA.

&&

.DISCUSSION...
Issued at 148 PM CDT Fri Oct 30 2026

Showers remain likely tonight into Saturday morning as low level
moisture deepens, roughly the lowest 5 km, and marginally dry,
cooler air above this layer allows for weak instability, generally
200-500 J/kg CAPE. This should generate mainly showers, but a few
lightning strikes will be possible. Rainfall amounts will mostly be
light, but some pockets of a tenth of two will be possible.

Saturday night into Sunday should be mostly dry, but moist neutral
soundings and lingering moisture/cloud cover may allow for some
patchy drizzle and showers. Overall low impact, but likely not an
entirely dry period.

A fairly well agreed upon trough of low pressure will move onto the
Plains Sunday night, deepening on Monday as a strong southern stream
jet strengthens. This should provide that area with widespread
rainfall and if everything comes together timingwise, the threat for
an isolated tornado over southeast parts of the area.

All models continue to indicate a widespread 1-2" of rainfall from
Sunday night into Tuesday morning. Very little disagreement for the
most part on timing and location of the rainfall. Given a fairly wet
pattern the past 6 weeks or so river flooding could start to become
a problem. But for now, the latest hydrologic modeling suggests at
least 2.5-4" of rain would be needed to push rivers to action stage
and minor flooding, so for now chances of river flooding are pretty
low (<20 percent). Also suggestions that 1.5" of rain in an hour
could produce some localized flash flooding, but for now the
rainfall rates should not be quite that high. All in all, it looks
like a band of warm advection rainfall will lift northward Sunday
night into Monday. Later Monday afternoon into Monday night a dry
slot could move in and if convection does not develop, a dry period
or period of drizzle will be possible. Then later Monday night into
Tuesday wrap around rainfall will move through.

While this is a very low threat probability, we will need to keep an
eye on the development of surface low pressure Monday afternoon as
the upper level wave moves through. Starting to see indications this
surface low pressure could end up near southeast SD/northwest IA
which could bring about a threat for some low topped
supercells/isolated tornadoes. The 6z ensemble data has the EC
placing this SFC low in southeast SD late Monday afternoon while the
GEFS and Canadian Ensemble are in eastern NE. Obviously a big
difference so trends will need to be monitored. The 12z GFS is now
placing the surface low in southeast SD late Monday afternoon as
well.

Tuesday will likely see some wrap around rainfall continue, but
should diminish throughout the day. Wednesday through Friday should
be mostly dry and cooler with highs from the upper 40s to mid 50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1231 PM CDT Fri Oct 30 2026

MVFR ceilings will continue to overspread the area from south to
north through the afternoon. These ceilings will further fall
into the IFR category after sunset through midnight for most
locations. Scattered showers and very isolated thunderstorms
will develop and move northward through the night into Saturday
morning. This activity will diminish from mid morning into
Saturday afternoon. Ceilings will then improve from south to
north through the day Saturday.

&&

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

&&

$$

DISCUSSION...08
AVIATION...08