420
FXUS65 KCYS 070000
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
500 PM MST Sat Dec 6 2025

.KEY MESSAGES...

- High wind warning has been issued for Arlington and Bordeaux
  areas for overnight into Sunday.

- Areas of blowing snow will impact travel conditions in the
  typical wind prone locations.

- Prolonged mountain snow will continue through early Sunday.
  The heaviest snowfall rates are expected this morning.

- There is potential for additional periods of high winds in the
  wind prone areas, with short lulls in between, on Sunday and
  again on Monday.

- A long duration, high-end, wind event is increasingly likely
  in the Tuesday through Thursday time period. Areas of snowfall
  will be possible too, but the details remain uncertain.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 300 PM MST Sat Dec 6 2025

High wind warnings have been allowed to expire or cancelled
early as winds have widespread weakened across the region this
afternoon. However, a fresh high wind warning has been issued
for our usual wind prone locations (Arlington and Bordeaux), but
this event looks a bit more marginal than the previous as in
house guidance shows probabilities only around 40-50%, but
knowing how the region can over perform combined with a
favorable Craig to Casper pressure gradient near the surface,
our gap locations should at least see a brief 58-60 mph wind
gust before the afternoon. Otherwise we had some over performing
snow this afternoon as a quick and stout band moved across the
region, bringing a brief inch or so of snow into Cheyenne
alongside some quick visibility reductions. As for our ongoing
winter products, the advisory for Arlington will likely be
allowed to expire in a few hours, with another few inches in the
mountains this evening before those warnings are allowed to
expire as well.

Into Sunday, brief ridging should help to bring the quieter
conditions to the region aside from some light mountain snow and
the aforementioned wind potential, but this just sets the stage
for the more complex setup we`ll be seeing next week as this
ridging fights an arctic airmass that will lead to high winds
and some lower elevation snow potential.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 300 PM MST Sat Dec 6 2025

It looks like we are still on track for a prolonged high-end wind
event in the long term that starts Monday, continuing into Thursday.
However, there remains some uncertainty due to the placement of an
amplifying ridge, or not, that builds across the West Coast. The
latest deterministic runs paint a similar picture, all have a stout
ridge building across the West Coast through Thursday, any variance
in placement and strength will be key in this afternoon`s forecast
package. If said ridge becomes more amplified, pushing north, this
will keep the strong upper level northwest flow pouring into our CWA
which will help keep the strong winds at the surface. Not only this,
but this scenario will maintain milder temperatures and drier
conditions. If this ridge at 500mb is less amplified, an arctic
front will dive south, promoting cooler temperatures along with a
break in the strong winds. With a surge of cooler temperatures with
an arctic front, if there is any precipitation that falls will be in
the form of snow. So, with this all being said, the forecast is
pretty tricky in the extended and for this afternoon`s package,
minimal changes/edits will be done in the long term to keep
continuity. So, with the needle pointing to the amplified scenario,
expect highs to top out in the 40s and 50s, cooler west of I-25. So,
lets get to the main story in the extended, a prolong high-end wind
event from Monday into Wednesday, possibly Thursday. Monday appears
windy, but by the nighttime hours, the winds really ramp up. A
strong upper level ridge will slide south, tightening the pressure
gradient. Ensemble members still have a 65 knot 700mb jet across
southeast Wyoming building into Tuesday. With these winds aloft,
negative Omega (GFS) will mix them down to the surface and expect
gusts to top out in the 70 to 80 mph range, strongest in the typical
wind prone areas across southeast Wyoming. Winds slowly wind down
through Wednesday and by Thursday they will rapidly diminish in the
afternoon hours. Like with anything, things can change and so can
model solutions, so stay tune for future updates.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 500 PM MST Sat Dec 6 2025

Upper level disturbance, which brought gusty winds and snow/rain
showers to the area since last night, is currently moving southeast
of the region. Northwest flow aloft will continue, but winds are
expected to subside into tonight. Primary forecast concern will be
low CIGS and some fog, especially for the western Nebraska
terminals.

HAZARDS/WEATHER TRENDS: VFR conditions expected to prevail over the
next 18 hours for the southeast Wyoming terminals. Westerly winds
around 15 to 20 knots this evening should diminish under 10 knots
until 12z to 15z. Can`t rule out a few snow showers, but coverage is
much lower compared to earlier in the day, so will keep out of the
TAF for now.

For western Nebraska, scattered rain/snow showers moving southeast
across the area this evening could impact KSNY and KBFF until 03z
with brief MVFR VIS. Otherwise, low CIGS are expected to develop
shortly and move south into the southern Panhandle by 06z. Currently
expected IFR to possibly LIFR CIGS. Fog is a little more uncertain,
but KSNY and KAIA have the best chance to see VIS below 2 miles
through from 04z to 15z Sunday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...High Wind Warning from 2 AM to 2 PM MST Sunday for WYZ106-110.
     Winter Weather Advisory until 5 PM MST this afternoon for
     WYZ110.
     Winter Storm Warning until 5 AM MST Sunday for WYZ112-114.

NE...None.

&&

$$

SHORT TERM...CG
LONG TERM...RZ
AVIATION...TJT