850
FXUS63 KFSD 130255
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
955 PM CDT Thu Mar 12 2026

.KEY MESSAGES...

- A High Wind Warning remains in effect through 7 am Friday
  morning. Northwest gusts of 55-65 mph expected with isolated
  gusts up to 75 mph possible.

- Light snow returns late Friday night into Saturday. Guidance
  is beginning to trend up slightly for this snowfall event, but
  still expecting light amounts at this time.

- A strong system moves into the area Saturday evening into
  early Monday. Strong winds and moderate to heavy snow are
  expected. A Winter Storm Watch for Blizzard conditions has
  been issued for locations along and northeast of a line from
  Chamberlain, South Dakota to Beresford, South Dakota to Storm
  Lake, Iowa line. Winter Storm Watch is in effect beginning
  Saturday evening into Monday morning.

&&

.UPDATE...
Issued at 940 PM CDT Thu Mar 12 2026

Winds are beginning to increase, a hour or two later than
previously expected. Huron Airport has seen a peak gust through
the time of this discussion of 70 mph, with a few other sites
close to or above that over the last hour or so. Expect winds
and gusts to continue to increase from west to east over the
next few hours. Gusts to 55-65 mph with sporadic gusts to 75 mph
are expected, so no planned changes to the on-going High Wind
Warnings.

Noticing a couple of trends this evening as the 13.00z data as
it begins to come in. With regards to snow chances Friday night
into early Saturday, latest guidance is showing a bit more
tightening in the snow band as the wave lifts north as well as
the 850mb and 700mb fronts. This tightening also seems to be
tied to strengthening frontogenesis (f-gen), likely around
700mb. Most of the area should see less than 2 inches of new
snow, but would not be surprised to see areas with locally
higher amounts. Depending on where exactly this falls, expect to
see some melting before the main show.

As for the Saturday evening to early Monday system, both 12.18z
and 13.00z guidance is showing a shift to the north, with some
NAM guidance shifting the heavier snow through the evening hours
north of US Hwy 14 (vs a bit further south toward I-90) and not
bringing snow to the Sioux Falls area until after midnight
Sunday. Now, we need to take this with a bucket of salt. Over
the last couple of years, models have shown this northern shift
in the track of a significant winter system roughly 48 hours
before onset just for the models to shift back to the south
within 24-36 hours of onset. We`ll be closely monitoring trends,
and folks with local and regional travel plans from Saturday
into early next week should continue to keep a close eye on the
forecast over the next 24 hours - be prepared to alter or cancel
travel plans.

&&

.DISCUSSION...
Issued at 250 PM CDT Thu Mar 12 2026

An active pattern is ahead with confidence for significantly
impactful weather increasing. Looking aloft at GOES water vapor we
can see the flow aloft is northwesterly with a 140-150 kt jet
streak. The exit region of which is located over the Tri-State area
through this afternoon and overnight. The resulting wind divergence
aloft will further enhance winds in the LLJ as surface convergence
increases and pressure falls ahead of an incoming Clipper system. As
we begin to mix higher into the boundary layer today we will tap
into that 30-40 kt LLJ. Gusts at the surface will increase through
the afternoon as a result, reaching 30-45 mph.

The clipper system places us in a strong WAA regime this afternoon.
However, there are a few details that may work to limit afternoon
highs. Clouds continue to flow in from the northwest, and have
advanced further south faster than previously anticipated. There is
also a chance for isolated to scattered rain showers and
thunderstorms this afternoon and evening, roughly between 3pm to
9pm. Soundings indicate a very dry subcloud layer, which will limit
how much actually reaches the ground. However, due to a 10 degree C
dewpoint temperature depression, evaporative cooling as rain falls
through the dry layer may produced severe wind gusts of 60+ mph.
This is outlined in the SPC Day 1 Marginal (level 1 of 5) outlook.
Considering this have decided to go with the slightly cooler NBM
highs for this afternoon. Along and south of a rough line from Huron
to Storm Lake highs will range from the low to upper 60s, warmest
along the southern Missouri River Counties. This area is also
expected to see the lowest relative humidity values, less than 30%.
To the north of that line highs will be in the 50s with higher
relative humidity values. Though we have some lingering
snow/snowmelt on the ground from yesterday, and the cooler highs
today, the low humidity and very strong winds keep Grassland Fire
Danger in the Very High to Extreme categories for this
afternoon. See the Fire Weather Discussion below for more
details.

Our next period of concern comes this evening and overnight as the
Clipper system drops southeast into Minnesota. The SPG continues to
tighten as pressure falls ahead of the cold front. The LLJ enhances
as divergence aloft increases. Temperatures in the mid-levels drop
rapidly 6-10 degrees C behind the front. All these factors will work
together to produce very strong winds beginning later this afternoon
and continuing through Friday morning. By 6pm CDT tonight gusts east
of I-29 will be between 25-35 mph. Areas to the west will be seeing
gusts 35-45 mph. As we continue into the evening gusts continue
to increase and spread southeastward. Widespread gusts of 55-65
mph are expected with isolated gusts up to 75 mph possible.
Winds remain strong through 4-6 am CDT when they will begin to
gradually taper off through Friday morning, becoming light in
the afternoon. Afternoon highs will be cooler thanks to the
northwesterly winds brining in cold air, reaching only the mid
30s to 40s.

Saturday will begin with light snow beginning to fall during the
early morning hours as warm air advection (WAA) strengthens aloft,
tightening the elevated frontal temperature gradient and also
strengthen the frontogenesis (FGEN) along it. The dendritic growth
zone (DGZ) will also be saturated with sufficient omega (upward
motion) in it to support a band of snow. The good news about this
band is that not expected to last long as the FGEN will be weakening
during the morning hours. Light snowfall is expected with this band
which looks to fall across near and north of I-90. Saturday
afternoon will be more on the dry side as the upper level wave
responsible for additional impacts will be pushing in from the
Northern Rockies. High temperatures look to warm to the 30s to up to
around 50F during the afternoon timeframe though depending on how
much snow falls during the morning hours, highs temperatures could
come down a bit.

Chances for snow will be increasing Saturday evening as WAA
restrengthens aloft. This in turn will re-tighten the temperatures
gradient and thus restrengthen the FGEN along the elevated front.
This will be the main show as strong QG ascent resides in the right
entrance region of an upper level jet. Snow will expand in coverage
through the rest of the evening and entire overnight hours. There
could be a small area of mixed precipitation on the leading edge of
the band of snow as the WAA just barely pushes temperatures above
freezing aloft. The strong front will translate southwards after
beginning around the highway-14 corridor. This will quickly cool the
warmed temperatures, turning any mixed precipitation back over to
snow. The strongest ascent will come during the overnight hours and
into early Sunday morning where the latest deterministic guidance
shows strong FGEN around 700 mb along with low stability and
negative equivalent potential vorticity (EPV) values above the
front. Thus, the bulk of the snow looks to fall during this period
of time. At the same time, winds will be strengthening as snow fall
rates increase. Gusts will be out of the east/northeast with gusts
strengthening up to 30-40 mph throughout the night. With such strong
winds in place as snow is falling, blowing snow is expected with the
falling snow. The best forcing for ascent will be sliding eastwards
throughout the morning hours on Saturday. This will gradually end
snowfall across the area from northwest to southeast. Though latest
trends keep snow chances going through the afternoon timeframe.
Winds will turn to out of the north during this period of time with
gusts further increasing up to about 50 mph. Snow will have the
potential to blow around after snow is done falling. Thus, blowing
snow looks to persist for the rest of Saturday even after the snow
finishes falling. Thus, have decided to issue a Winter Storm Watch
for Blizzard conditions. The Watch is in effect from Saturday
evening through Monday morning as the weakening winds will still
result in some blowing snow through Sunday night. Snowfall amounts
at this time look to be impactful with the ensembles showing a 40-
90% chance for snowfall totals to exceed 6 inches mainly along and
northeast of a Chamberlain, South Dakota to Beresford, South Dakota
to Storm Lake, Iowa line. The highest probabilities lie across
southwest Minnesota. The ensembles spread increases up to a foot of
snow where the probabilities span from a 20-60% chance, highest
again across southwest Minnesota. This combination of wind and
snowfall looks to bring the most impactful winter storm of the
season to the area. While details can change heading into this
event, please continue to monitor the latest forecast for the most
up to date information.

The rest of the next week looks to begin on the cold side and slowly
warm throughout the week. There could be additional chances for snow
during the middle of the week but details are uncertain.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 637 PM CDT Thu Mar 12 2026

Mostly VFR conditions through the period, with some MVFR
stratus and possibly MVFR visibility with heavier rain showers
through this evening. Mid clouds prevail during much of the TAF
period.

Winds shift late this evening to northwesterly and quickly
strengthen from west to east as we begin to mix into the robust
LLJ. Gusts around 55 knots are expected late this evening and
into the early overnight hours. Strongest gusts are expected to
last for around 4-6 hours at any one location. May see a couple
of hours of LLWS at KSUX, but conditions appear marginal with
the timing of the increase in the speed of surface winds
(concern would be with speed shear). Removed mention of LLWS at
KHON and KFSD, as direction is expected to be within 30 deg
and with gusts around 50 kts and speed at 2kft around 60 kts
leading to little (relative) difference in the speed shear.
Winds taper down through the morning hours Friday, with gusts
around 20-30 knots for areas west of IA/MN State Hwy 60 by
daybreak. Gusts around 20 knots expected during the day Friday.

Precipitation chances begin to move in to south central SD
toward the end of the TAF period, but not expected any impacts
to TAF sites through this cycle.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...High Wind Warning until 7 AM CDT Friday for SDZ038>040-050-
     052>071.
     Winter Storm Watch from Saturday evening through Monday
     morning for SDZ040-056-062-067.
     Winter Storm Watch from Saturday evening through late Sunday
     night for SDZ038-039-052>055-057>061.
MN...High Wind Warning until 7 AM CDT Friday for MNZ071-072-080-081-
     089-090-097-098.
     Winter Storm Watch from Saturday evening through Monday
     morning for MNZ071-072-080-081-089-090-097-098.
IA...High Wind Warning until 7 AM CDT Friday for IAZ001>003-012>014-
     020>022-031-032.
     Winter Storm Watch from Saturday evening through Monday
     morning for IAZ001>003-012>014-021-022.
NE...High Wind Warning until 7 AM CDT Friday for NEZ013-014.

&&

$$

UPDATE...SG
DISCUSSION...Meyers/AJP
AVIATION...SG