056
FXUS63 KFSD 310430
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1130 PM CDT Fri Oct 30 2026

.KEY MESSAGES...

- Showers and very isolated thunderstorms will continue tonight
  into Saturday morning. 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.

&&

.UPDATE...
Issued at 855 PM CDT Fri Oct 30 2026

The forecast remains on track at issuance of this update. Light
scattered showers and thunderstorms will continue to move
northeast through the remainder of the overnight. Rainfall
amounts are expected to remain low with only a trace up to a
tenth or two. Soundings indicate most of the region will become
near saturated to saturated in the boundary layer. This will
result in very low stratus to fog formation overnight. Ensemble
guidance indicates around a 30% chance for visibility to fall to
2 miles or less at times. Near sunrise showers should begin to
taper off, stratus begins to lift, and any fog dissipates. Most
of the day will then be dry. Skies look to remain mostly
cloudy, however surface WAA on breezy southerly winds will warm
afternoon highs into the upper 50s to low 60s. Afternoon gusts
of 15-25 mph will taper off after sunset.

Saturday evening and through the overnight a southern stream short
wave works northeast into the area. This will bring another round of
scattered, very light showers. Some weak elevated instability may
allow for a few lightning strikes as well, but severe weather is not
anticipated. Once again only a few hundredths to a tenth or two is
expected. Showers taper off through the morning and Sunday afternoon
should be dry. Diurnally breezy southerly winds will once again
usher in mild WAA boosting highs into the 60s for most of the
region.

Late Sunday evening a much stronger upper trough will push into the
region from the west, bringing widespread chances for accumulating
rainfall overnight and through Monday. For more details on this
system please refer to the Discussion below.

&&

.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 /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1129 PM CDT Fri Oct 30 2026

A mix of MVFR down to LIFR will prevail for the first half of this
period. Scattered showers and thunderstorms will continue to move to
the northeast through the overnight, gradually tapering off through
mid-Saturday morning. Low stratus and possibly patchy fog lingers
into Saturday afternoon before ceilings begin to lift to MVFR, and
possibly up to low VFR along and east of I-29 Saturday late
afternoon and evening. Additional chances for scattered light
showers return late Saturday evening.

Light southeast winds will gradually increase after sunrise and
become southerly. Breezy afternoon gusts of 20-25 kts are expected
for areas west of I-29, generally 20 kts or less to the east. Winds
decrease after sunset but remain on the breezy side with gusts
around 15-20 kts through the end of the period.

&&

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

&&

$$

UPDATE...AJP
DISCUSSION...08
AVIATION...AJP