682
FXUS65 KCYS 220520
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1020 PM MST Fri Nov 21 2025

.KEY MESSAGES...

- A disorganized storms system will bring the next chance for
 a mix of rain and snow Sunday into Monday, mainly for our
 southeastern zones.

- Wind speeds will increase Monday for the wind prone areas
  ahead of a powerful cold front poised to bring much colder
  temperatures for Tuesday and Wednesday.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 358 PM MST Fri Nov 21 2025

A temporary ridge will move overhead in between our last system and
the next one pushing in at the beginning of the week. 700mb
temperatures will be around 4C celsius translating to high
temperatures in the 40`s and 50`s. Also while in between the two
systems the pressure gradient will tighten slightly to give us some
breezy winds up to 25 mph in the afternoon on Saturday. Thankfully
any signal for high winds dont appear to show up this weekend.
However, we will have a few clouds traversing through the region to
give us some partly cloudy skies but no precipitation. Residual
moisture with some slight moisture advection will be present through
the weekend but again this will not result in any precipitation
falling. This residual mositure will translate into a slightly
higher relative humidity percentage across the region crossing off
any fire weather concerns that a ridge may present.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 358 PM MST Fri Nov 21 2025

An unsettled weather pattern will carry us through Thanksgiving week
across our area. The first system to watch will be yet another
disorganized closed low ejecting from the southwest on Sunday into
Monday. This will be underneath a ridge that will remain fairly
strong for this time of year. As a result, snow levels are expected
to be exceptionally high once again, such that most areas that see
precip may remain as mostly rain. The best chance for any
precipitation will be in our southeastern zones, just like the most
recent departing system. Just how far west moisture extends is
uncertain, and will determine if there is any snow with this event.
With snow levels hovering around 6000 ft, Nebraska can anticipate
just rain showers. There is less confidence in precip of any kind
extending west into Wyoming, so just a slight chance for snow is
included mainly for southern Albany and western Laramie counties.

Once the ejecting closed low rejoins with the primary jet stream on
Monday, expect the pressure gradient to increase rapidly across the
area, bringing an abrupt end to our break from strong winds. GFS-
based in-house guidance shows high (75%+) probabilities for high
winds in our wind prone areas. Of course, it is worth mentioning
that the deterministic GFS is a bit more aggressive than the multi-
model mean at this time, but there is strong support for at least
elevated wind speeds. For now, winds were raised to just about equal
to high wind criteria and we will continue to monitor this in the
coming days to find better model consistency. The increase in
gradients occurs ahead of the next system which will be a powerful
Pacific cold front. This is expected to arrive late Monday or early
Tuesday. Temperatures will be sent plummeting into Tuesday, while
winds likely remain quite strong. This sets the stage for a fairly
unpleasant day Tuesday with temperatures mostly in the 30s and
breezy to windy conditions continuing. Ensembles have generally
converged on a storm track mostly to our north, which will minimize
the chance for precipitation. Precipitation type will not be a
concern with this system, as strong cold air advection will quickly
drop snow levels to below ground level for the entire area. However,
moisture will be highly limited, and thus PoPs are quite modest and
mainly confined to typical northwest flow areas of the higher
mountains and the US-20 / Pine Ridge area.

A warming trend will resume Wednesday through Friday as the
departing upper level low moves off to the east and ridging tries to
expand from the west. Ensemble spread is quite large for this
period, but confidence is fairly high in temperatures return to at
least near average. Depending on how fast ridging takes back over,
we may have to watch for a weak shortwave riding over the top of the
ridge on Thanksgiving Day. If the ridge advances more slowly
(favored by a cluster of about 40% of members, mainly from the ECWMF
ensemble system), there will be another shot at some light snow
accumulations for the area Wednesday into Thursday. A faster ridge
(favored by the 60% of members more heavily from the GEFS) would
mean a quicker warm-up and largely dry conditions for the holiday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1020 PM MST Fri Nov 21 2025

BR that moved in briefly and reduced VIS at KCYS has now dissipated
and for the remainder of this TAF period, no widespread aviation
weather concerns expected across all terminals. KLAR, KBFF, and KAIA
may have BR develop overnight along with lower clouds, but this
should not have any aviation impacts. Winds will not be much of a
factor as they are expected to remain generally 10 knots or less
through this TAF period.

&&

.CLIMATE...
Issued at 358 PM MST Fri Nov 21 2025

While outside of the operational forecast period, there is an
unusually consistent signal for a period of active winter weather
beginning Saturday or Sunday November 29-30 and carrying into the
first week of December. Nearly all ensemble members show a dramatic
cool down sometime during the weekend after Thanksgiving. 75% of
ensemble members have 700-mb temperatures below -8C in Cheyenne and
under -11C in Douglas. In addition, nearly all members have some
amount of light to moderate snowfall. Ensemble-based snowfall
forecasts already show a greater than 50% chance of greater than 1"
for the entire area for the 48-hour period ending Monday morning,
December 1. We normally do not discuss things like this outside of
the 7-day operational forecast period, but ensembles are remarkably
consistent in a period of much colder temperatures and more frequent
chance for snowfall beginning next weekend and carrying into early
December. The Climate Prediction Center has been hinting at this
potential pattern change for weeks now. On the global scale,
observed warming temperatures in the polar stratosphere combined
with a Rossby-wave train produced by tropical convective activity in
the western Pacific Ocean associated with the Madden-Julian
Oscillation both favor cold snaps in central North America days to
weeks later. It is still uncertain whether this push of cold air
will be focused over the west-central or east-central portion of the
country (which could have major implications on the details of the
forecast for our area), but since this is coincident with a major
period of holiday travel across the country, we thought it would be
worth a special mention today. We will be monitoring this closely
over the upcoming week.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...MM
LONG TERM...MN
AVIATION...RZ
CLIMATE...MN