922
FXUS65 KCYS 222145
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
245 PM MST Sat Nov 22 2025

.KEY MESSAGES...

- A disorganized storms system will bring the next chance for a
  mix of rain and snow Sunday into Monday,and the potential for
  high winds.

- We are monitoring the potential for an arctic cold front to bring
  cold temperatures and a chance for accumulating snow for the
  end of the Thanksgiving long weekend.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 245 PM MST Sat Nov 22 2025

Mid-level and low level water vapor highlights a little stream of
dry air working its way north into our area. Behind this thin stream
of dry air is a plume of moisture ahead of our next system currently
over southern California. This stream of dry air will help us
maintain clear skies throughout the day. Although the models do show
some clouds working their way over Carbon county tonight before
dissipating Sunday morning. That low pressure system will move
Northeast entering the Intermountain West by Sunday afternoon. By
Sunday evening the low is projected to sit over the
Kansas/Colorado/Nebraska area increasing our precipitation chances
for the southern panhandle and the eastern portions of the
Southeastern Wyoming area. By Monday morning the low is expected to
be further east into the Northern Plains ending our precipitation
chances. Even though this system occurs over night almost all the
precipitation falling is expected to remain as rain. There is enough
warm air advection with this system that 700mb temperatures are
expected tor remain above 1C. However, Rain/snow mix was kept in the
grids due to the chance of portions of Southeast Wyoming drop below
0C as the system pushes east "cooling" off the precipitation enough
to allow some small percentage to remain as snow. No measurable
amount of snow accumulation is expected though. As this system
enters the Northern Plains there is a very small break from
precipitation Monday. A shortwave trough will descend down from
Alberta starting to tighten the pressure gradient across our region.
As this trough descends downward a 700mb jet starts to develop to
increase the wind speeds across the Southeast Wyoming area. By the
late afternoon the 700mb jet will strengthen developing winds
between 55 and 65 knots across our wind prone areas. The GFS omega
fields show an increase in subsident flow as 850/700mb lapse rates
also increase near the favorable 8-9C range. This primes the region
for possible high winds Monday afternoon through Tuesday morning.
However, there are some models with weaker winds not exceeding above
56 knots so any high wind headlines were held off for now. An
attendant cold front looks to start to push through the region late
monday afternoon to evening timeframe. This cold front will be the
lifting mechanism for our second round of precipitation chances for
the region starting in Converse county and moving South-southeast.
Given the Semi-arctic air that follows this front, not a lot of
precipitation is currently expected with this system. However, any
precip that falls will start out as rain and quickly turn into snow.
700mb temperatures are currently progged to drop between -10 and
-15C. This semi-arctic air will drop overnight temperatures into the
teens for the mountainous regions West of I-25 and into the low 20`s
for the lower elevations east of I-25.


&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Issued at 245 PM MST Sat Nov 22 2025

A brief taster of wintry temperatures is on track for Tuesday. A
strong but fast moving Pacific cold front will be clear through the
area by Tuesday morning, leaving much colder temperatures and breezy
northwest winds. 700-mb temperatures plummet to around -10C to -14C
behind the front, which is not too unusual for this time of year,
but may feel chillier coming off of what has been an exceptionally
warm November so far. Highs will largely be in the upper 20s to 30s
with wind chills in the teens and 20s as a result of gusty northwest
winds. Unfortunately for our near record low mountain snowpack, this
system does not appear likely to bring much snowfall. Light snow
showers are favored into Tuesday morning for our northern zones and
southern mountains, but QPF scenarios are unimpressive. Even the
90th percentile snowfall remains at a fairly dismal 0.25" of liquid
for the higher peaks of the Sierra Madre and Snowy ranges. Average
SWE deficits compared to median in each range are nearly ten times
that.

This system will race off to the east by Wednesday, leaving a
northwest flow pattern over the Rockies as ridging tries to expand
back to the east. A powerful jet stream is expected to round the top
of this ridge, with a decent amount of Pacific moisture embedded.
Exactly where this moisture plume sets up will determine if light
mountain snow chances continue Wednesday into Thursday, or if we dry
out once again and remain so into the Thanksgiving holiday. GEFS
members generally show the ridge expanding just a little faster,
enough to shunt the moisture plume away from our mountains, but
ECMWF members tend to keep light snow in the southern Wyoming
mountains into Thanksgiving Day. Low end PoPs and minimal QPF are
retained in the official forecast for the mountains. Precipitation
can`t quite be ruled out for populated areas Wednesday into early
Thursday, but with only about 10 to 15% of members showing anything
at all, PoPs are below slight chance at this time. Regardless of the
precipitation outcome, our position under the right exit region of a
strong jet aloft will favor descent and thus at least elevated wind
speeds returning after a brief lull late Tuesday into early
Wednesday. An early look into high wind parameters suggests a fairly
unimpressive MSLP gradient across the barrier, but decent 700-mb
wind speeds and height gradients. This tends to point more towards
an Arlington/Elk Mountain event rather than something for all wind
prone areas, but there is plenty of time for this to change. For
now, winds were increased slightly over NBM guidance but are
currently below high wind thresholds. Look for a return of near to
slightly above average temperatures for Thursday and Friday across
the area as 700-mb temperatures recover to near 0C for the period. A
cold surface high over the plains may keep an inversion over
northern or eastern portions of the area and cap temperatures below
the potential exhibited by these values aloft, but this is a little
too much detail to get into at this lead time.

At the very end of the operational forecast period, ensembles
continue to display unusually strong consistency in another major
cold front. There is disparity in the strength and timing of this
event, as well as how much snowfall might accompany this front, but
confidence is fairly high (relative to typical day 8+ forecasts) in
a major change to colder temperatures beginning around Saturday or
Sunday. Ensemble median 700-mb temperatures fall to -12C at KCYS and
-15C at KDGW, with nearly all members dropping temperatures below
average by Sunday. The vast majority of members also have light to
moderate snow falling across most of the area, which is again quite
unusual for this lead time. 75% of members have widespread 1" or
more of snowfall. A major snowstorm does not appear particularly
likely, but there is fairly good confidence in some form of a light
to moderate snowfall event between Saturday 11/29 and Monday 12/1.
Since this coincides with a busy period of travel across the
country, it is worth some early discussion here. We will continue to
monitor this over the week ahead.


&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1029 AM MST Sat Nov 22 2025

VFR conditions are expected for the forecast period. Winds will
generally be light today, but we may see a few gusts to around
20 knots, decreasing after sundown.

&&

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

&&

$$

SHORT TERM...MM
LONG TERM...MN
AVIATION...MN