104
FXUS65 KCYS 282035
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
135 PM MST Fri Nov 28 2025

.KEY MESSAGES...

- An arctic front will move across the region tonight, bringing
  much colder temperatures along with light snowfall
  accumulations to the forecast area through the weekend.

- Very active long term forecast expected with multiple troughs
  moving through and promoting snow chances, as well as a high
  wind event possible Tuesday.

- Temperatures will remain very cold through mid-week, before a
  weak warming trend arrives Wednesday onwards.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 135 PM MST Fri Nov 28 2025

The big story in the short term will be the arctic front that dives
south across the CWA late this evening and through the overnight
hours. But first, enough lift and instability is in place to
increase precipitation chances this afternoon. Scattered light snow
showers will begin west of the I-25 corridor and spread east. As it
does, some of the precipitation may transition to a rain/snow mix or
all rain with a northern surge of warmer air in the mid-levels,
helping surface temps climb into the 40s and 50s for many locations,
warmest east of I-25. By this evening, as the front approaches, in-
house guidance depicts decent parameters for the likelihood of snow
squalls, with the greatest threat west of Cheyenne. Timing will play
a big role, winds are slated to decrease this afternoon which limits
the snow squall potential, but this will be monitored as any burst
of snow could reduce visibility along highways. Then we go into the
late evening and overnight hours, as the arctic front approaches
closer to the CWA, widespread snow chances increase along with winds
shifting and becoming gusty from the north. With north winds,
orographic enhancement will increase snow totals, places such as
Pine Ridge or any city on a north facing slope. Snow accumulations
appear to be minor in the Cheyenne area, generally less than an
inch, while higher amounts to the west and north, with many places
seeing 1 to 4 inches, greater in the mountains and along Pine Ridge.
Due to orographic effects along with higher QPF values, Pine Ridge
could see snowfall totals in the 3 to 5 inch range. With a swath of
up to 5 inches of snow stretching from Converse east to Dawes
County, Winter Weather Advisories are in affect from 8 PM tonight
into Saturday morning. Confidence is high regarding snowfall amounts
due to good agreement between the deterministic models and
ensembles. As mentioned earlier, winds will shift to the north, this
will allow a surge of cold Canadian air to move into the CWA, making
temperatures plummet tonight with lows bottoming out in the low
teens to single digits in many places.

This front and associated precipitation will have pushed off to the
east by Saturday, with any lingering snow showers ending by the
early afternoon hours. Cold air will have settled in, and don`t
expect that thermometer to rise much for the high, as highs Saturday
look to only top out in the teens to 20s while lows plummet once
again to near zero, especially across eastern portions of the CWA,
where skies remain clear longer.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 135 PM MST Fri Nov 28 2025

Fairly active long term weather forecast for southeast Wyoming and
western Nebraska as multiple troughs dig through the region
throughout the week. On Sunday, the first upper-level trough
expected this week is progged to push into the Intermountain West
early Sunday morning before strengthening through the late-morning
hours. Ample 500mb cyclonic vorticity advection will eject out from
the jet and push across the CWA. In combination with the left exit
region of the upper-level jet across the CWA, ample synoptic lift is
expected with this positively tilted, upper-level trough. 700mb flow
will remain fairly messy, as a closed 700mb low attempts to develop
before transitioning to an open wave east of the CWA. Despite the
messy flow, southeasterly 700mb flow is expected across the Sierra
Madre and Snowy Ranges, which is a favorable upslope flow regime,
specifically for the Sierra Madres. Snow is expected to start across
the higher terrain as early as 12Z Sunday morning. With ample lift
and moisture across the region, mostly cloudy skies will develop and
keep the region cold for an additional day. As the 700mb system
pushes through, a surface trough will develop with an attendant cold
front, dropping 700mb temperatures into the -12 to -10C range, from
the -9 to -6C range, by the early morning hours Monday. As a result,
surface high temperatures will remain in the teens to 30s for the
entire region, with overnight lows into Monday morning in the single
digits. Luckily, winds should remain fairly light throughout the day
Sunday, though they will be strong enough to drop the apparent
temperatures into the teens across southern portions of the region
and single digits across the furthest north locations. Overall,
another chilly day expected Sunday, prolonging this cold snap into
next week.

Cold conditions will continue into the day Monday as the upper-level
trough pushes over the CWA, funneling continental arctic air from
Canada into the region. The trough will begin to pinch off
throughout the day Monday as the next upper-level trough from Canada
digs into the northwestern CONUS, with very brief ridging possible
early Tuesday morning. The departing and weakening upper-level
trough will keep 700mb temperatures in the negative single digits
Monday, before a briefly warming into the -3 to 0C range for the
early morning hours Tuesday. With the transitioning upper-level
pattern, Monday will be mostly dry, though cold. Surface high
temperatures will remain in the mid-20s to mid-30s Monday. Winds
begin to increase throughout the day Monday, with high winds
possible on Tuesday. With the cooler temperatures and increasing
winds, apparent temperatures will remain in the teens to 20s for the
afternoon on Monday. Overnight lows Monday into Tuesday will be a
bit warmer, thanks to the brief upper-level ridging expected Monday
night into early Tuesday morning. Tuesday morning lows will only
bottom out in the teens to mid-20s, much warmer than the single
digits from the night before.

The warming will be short-lived as the upper-level ridging quickly
gets shunted to the east early Tuesday afternoon and the next upper-
level trough pushes into the region. Snow chances increase west to
east on Tuesday as the positively tilted, upper-level wave moves
into the region and the CWA once again remains in the left exit
region of the upper-level jet. 700mb temperatures will tank back
into the -10 to -8C range Tuesday afternoon and evening as the
attendant cold front surges through. Prior to the cold front
arriving, a brief zonal pattern will develop across the CWA Tuesday
morning into the afternoon hours at 700mb. A brief period of
enhanced height gradients at 700mb will increase the low-leve jet to
around 50 to 55kts, with pockets around 60kts, across the Laramie
Range. Downward omega values increase Tuesday morning and afternoon
as well, leading to ample downward mixing through the day. In
addition to this, the Craig to Casper 850mb gradient increase to
over 70m, with the 700mb gradient approaching 60m. In house guidance
is very excited about this event, with a 90% probability of high
winds at Arlington and 70% probability at Bordeaux. With all these
factors combined, strong to near-high winds are likely Tuesday
afternoon in the wind-prone regions.

The remaining long term period is dominated by upper-level
troughing, cold 700mb temperatures, and daily snow chances across
the region. The previously mentioned trough stays over the region
through Friday before the next upper-level trough moves in and
pushes the aforementioned trough off the east. Temperatures for the
remaining week will warm slightly, though 20s, 30s, and 40s are
still likely across the region. In-house guidance is hinting at
another high wind potential Friday, with about a 50% probability at
this time. Things will still change between now and Friday, but did
start increasing the winds late in the period to start hinting at
the next possible high wind event across the region.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1035 AM MST Fri Nov 28 2025

KAIA and KSNY have been plagued by low CIGs, they should lift over
the next few hours as a potent cold front begins its trek south
towards our CWA. Ahead of this front, scattered rain and/or snow
showers are likely and will spread across the CWA through this
afternoon. Aviation impacts will be minimal; however, a snow shower
moving over a terminal may briefly reduce VIS. On the wind front,
gusty west winds will impact KRWL and KLAR at the start of this TAF
period. These winds will ease around sunset, but ramp up again later
this evening and into the overnight hours as the aforementioned front
moves into our CWA. Expect the strongest winds to impact terminals
east of the I-25 corridor. With this FROPA, winds will shift to the
north along with bringing widespread snow showers, this will likely
reduce VIS and lower CIGs later this evening into tonight for all
terminals.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 8 PM this evening to 8 AM MST
     Saturday for WYZ101-102.
NE...Winter Weather Advisory from 8 PM this evening to 11 AM MST
     Saturday for NEZ002.
     Winter Weather Advisory from 8 PM this evening to 8 AM MST
     Saturday for NEZ095.

&&

$$

SHORT TERM...RZ
LONG TERM...AM
AVIATION...RZ