727
FXUS63 KFSD 250448
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1048 PM CST Mon Nov 24 2025

.KEY MESSAGES...

- Fog, including dense fog with visibility below half a mile,
  continues overnight into the Tuesday morning commute.

- Rapidly intensifying storm system will bring strong winds
  Tuesday with widespread 45 mph gusts likely by the afternoon.
  Gusts to 60 mph are likely in the MO River valley.

- Rain changing to snow expected as far south as I-90, with
  accumulating snow expected. Evening trends have been shifting
  higher snowfall southward. Visibility impacts may be possible
  in snow and wind into Tuesday evening.

- Holiday travel less likely to be impacted through
  Thanksgiving, but greater travel risks develop Friday through
  the weekend. Considerable uncertainty remains, but
  probabilities for 1" snow near 90%, and 3" greater than 50%.

&&

.UPDATE...
Issued at 1025 PM CST Mon Nov 24 2025

A couple of things to note late this evening. First, fog
continues to expand over the area. Dense fog with visibility
below half a mile has remained generally transient and patchy
until about the last hour or so. May need a Dense Fog Advisory
within the next hour or two should observations continue to
deteriorate across the US Hwy 20 corridor into northwestern IA.

Second, 24.21z SREF and 25.00z hi-res guidance overall has
shifted southward with the axis of heavier snowfall. This would
bring higher totals than currently forecast - especially across
southwestern MN. Still awaiting some of the other 25.00z
guidance to come in, but would not be surprised to see an
increase in amounts and possible headline changes.

&&

.DISCUSSION...
Issued at 209 PM CST Mon Nov 24 2025

THIS AFTERNOON: Mid-lvl vorticity sliding through the mid-Missouri
River valley this afternoon continues to produce very light
rainfall across portions of the Tri-State area this afternoon.
Any QPF amounts are going to remain light.

TONIGHT:  Short term guidance continues to hint at the potential for
scattered fog to develop late this evening as winds remain light and
boundary layer moisture remains elevated.  Coverage of fog remains
too uncertain to issue an advisory at this point, but will need to
monitor trends this evening.  A fast moving open wave currently
through the Northern Rockies will race into the Northern Plains
overnight. An increase in mid-lvl clouds will continue tonight, with
warm advection precipitation focusing well north of the CWA. However
an initial surge of low lvl cold air advection will enter the
Missouri River valley region by daybreak with a rapid increase in
winds likely.

TUESDAY:  The aforementioned wave will continue to deepen as it
crosses the Dakotas and pivots slightly southeast in the afternoon.
Winds will spread through the MO River valley on the initial
surge of 925:850 mb cold air advection pushing higher terrain
areas of the river valley near high wind warning criteria into
mid-morning. Scattered rain showers may also develop on the
first synoptic surface boundary moving west to east mid-morning,
but coverage will stay on the lower side. A stronger synoptic
cold front pivots around the backside of the upper trough by
mid-day, with deeper cold advection and stronger downward
momentum transfer to the surface through the remainder of the
CWA. HREF guidance along with most deterministic guidance
suggests high potential for gusts 40 to 50 mph through the Tri-
State area into the evening. Will issue a localized high wind
warning for the higher terrain areas of the MO river valley with
a wind advisory elsewhere. Precipitation will also wrap round
the passing trough by mid-day, spreading a risk for light rain
turning to rain/snow and then to snow through the afternoon.
Undercutting low-lvl dry air may limit the southern extent of
precipitation, with greater focus for accumulating snow near and
north of Highway 14 where probabilities of 1"+ snow rise above
60%. While the wind will lead to some tricky travel at times,
anyone traveling northward in the state along Interstate 29
north of Brookings and Watertown will need to remain weather
aware.

WEDNESDAY:  High pressure moves into the region for Wednesday as
this system moves well east of the area.  A very cold day is likely
with highs struggling to rise out of the 20s. Overnight lows by
Thanksgiving morning fall into the teens and may be lower in any
area that experiences accumulating snowfall.

FRIDAY-MONDAY:  Uncertainty is the key word in the forecast for the
post holiday travel timeframe from Friday through Sunday.  Mid-lvl
ridging begins to increase late Thursday ahead of a deepening West
Coast trough.  Guidance is converging on a solution that will place
a warm advection zone of snow through the Plains on Friday, with a
minor short wave crossing the advection zone enhancing lift locally.
 The difficult challenge is pin pointing where this area of
precipitation develops. The GFS is further northeast with this
precipitation, with the ECMWF/CMC deeper and stronger with the
overall lift. Ensembles are also suggesting a fairly narrow corridor
of precipitation, with probabilities of 0.10+" over 70% from
Friday afternoon into Saturday morning. Probabilities of 0.50"+
are near or less than 10%, so depending on ratios this would
suggest an average 1-4" snow into Saturday morning. Have
increased PoPs into Friday night for portions of the CWA over
NBM guidance.

By Saturday, model agreement mostly falls apart as significant
differences remain between extended models on the 500 mb pattern
through the weekend.  The ECMWF/CMC both a large and deeper phased
trough over the central US, effectively shoving any secondary round
of winter weather well south of the region.  The GFS on the
other hand splits the flow, holding back a significant portion
of the upper trough over the southwestern US and creating a more
impactful pattern for widespread impacts through the Plains on
the weekend. Ensembles are still spread considerably this
weekend, leading to less than typical confidence this far out in
the forecast. A larger majority of the ECMWF members support
the drier solution than those of the GFS at this time. If
traveling for the holiday, continue to monitor the forecast!

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1025 PM CST Mon Nov 24 2025

Messy forecast through the period with stratus, fog, precip, and
wind concerns.

1. MVFR/IFR stratus prevails through much of the period once
ceilings drop. MVFR/IFR and even patchy LIFR fog is expected
through at least daybreak. Areas along the MO River to US Hwy 20
may see brief returns to VFR late Tuesday morning into the
afternoon, but should return to MVFR.

2. Precipitation moves into the area, initially as rain but
changing over to snow. Guidance has started trending south this
evening, but still think precipitation will remain focused along
and north of I-90. Snow accumulations are expected, with highest
amounts toward US Hwy 14. Expect continued visibility
restrictions with falling and blowing snow.

3. Northwesterly winds increase from west to east overnight and
into Tuesday morning. By early afternoon, gusts to 50 knots are
expected in south central SD. Gusts 30-45 knots will be common
elsewhere, and taper off from west to east toward the end of the
period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 9 AM to 9 PM CST Tuesday for SDZ068>071.
     Wind Advisory from 9 AM to 6 PM CST Tuesday for SDZ038-052-053-
     058-059-064.
     Wind Advisory from noon to 9 PM CST Tuesday for SDZ039-040-
     054>056-060>062-065>067.
     High Wind Warning from 6 AM to 6 PM CST Tuesday for SDZ050-057-
     063.
MN...Wind Advisory from 3 PM Tuesday to midnight CST Tuesday night
     for MNZ071-072-080-081-089-090-097-098.
IA...Wind Advisory from 3 PM Tuesday to midnight CST Tuesday night
     for IAZ001>003-012>014-021-022-032.
     Wind Advisory from 9 AM to 9 PM CST Tuesday for IAZ020-031.
NE...Wind Advisory from 9 AM to 9 PM CST Tuesday for NEZ013-014.

&&

$$

UPDATE...SG
DISCUSSION...Dux
AVIATION...SG