417
FXUS65 KCYS 042036
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
136 PM MST Thu Dec 4 2025

.KEY MESSAGES...

- Winds remaining elevated through Friday morning in the wind
  prone areas. Another round of High Wind Warnings continue.

- Areas of blowing snow today may impact travel conditions in
  the wind prone areas of southeast Wyoming.

- Prolonged period of mountain snow expected tonight through
  Sunday morning. Winter Storm Warnings have been issued for
  Sierra Madre and Snowy Ranges.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 130 PM MST Thu Dec 4 2025

A prolonged northwest flow pattern over southeast Wyoming and
western Nebraska will result in heavy snowfall in the mountains
and windy conditions in the typical wind-prone corridors of
Wyoming through the short-term. Forecast guidance remains on
track this afternoon with no major shifts or changes over the
last 12 hours of guidance cycles. Strong flow aloft in the
700-500mb region along with favorable height and pressure
gradients over south-central Wyoming will continue to result in
surface winds gusting near or over 60 mph this evening and
overnight. The strongest winds will likely remain confined to
the Snowy Range Foothills along I-80 as well as the central and
southern Laramie Range given the more marginal nature of
typical parameters indicative of more easterly spread in high
winds. Gap flow east of the Laramie Range over I-25 does still
look to shut down by around daybreak on Friday with lower wind
speeds expected east of the Laramie Range throughout the day.

With regard to precipitation, several waves of moisture are
still on-track to affect the higher terrain of southeast Wyoming
tonight through Saturday. The first wave will arrive around
midnight tonight as evidenced by increasing saturation in
forecast soundings above 700mb. Soundings dry somewhat by
Friday afternoon, likely leading to a decrease in snowfall rates
in the higher terrain. Then, a more potent plume of moisture
originating in the northern Pacific will traverse the northern
Rockies and reach southeast Wyoming by the evening hours on
Friday. This event will last right through Friday night and
Saturday bringing heavy snow over 1-2 feet in the Sierra Madre
and Snowy ranges. This afternoon`s ensemble guidance has
increased QPF totals slightly, adding even more confidence to an
already very confident forecast. It is possible that some
locations in the higher terrain may see nearly 3 feet of snow
before this event ends in the Long-Term forecast period on
Sunday. Farther east outside of the mountains, expect westerly
flow to contribute to a light downslope pattern. This will
result in slightly warmer days from Cheyenne eastward, including
Scottsbluff and the remainder of the NE Panhandle. Highs will
return to near average on Friday with overnight lows near
average as well given thin high cloud cover spilling in from the
west. Overall a high confidence forecast in the short-term with
only minor changes to QPF totals in this forecast package.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 130 PM MST Thu Dec 4 2025

Synopsis...

Ensemble clusters continue to depict northwest flow across the
central and northern Rockies through next week with slight
variations in the zonal vs meridional component by early next week.
Overall, with ridging centered over or just offshore southern
California and dominant troughing from the Hudson Bay into the
Canadian Maritime, it does not look to be a particularly
amplified pattern the next several days with low amplitude
shortwaves keeping active precipitation chances in the mountains
which occasionally spill into the adjacent zones and high
plains through the period. Temperatures will gradually warm
through the end of the period with highs on the front range and
NE panhandle reaching into the 50s early next week. Most notably
through the extended will be periods of high to very high winds
especially early in the coming week.

- Snow Chances

As the lead shortwave mostly misses the area to the east on Friday a
second wave will more directly impact the area Saturday bringing
better moisture to the high elevations where snow will continue
through the day on Sunday. From Saturday morning through Sunday
things look to improve with regards to snow rate with only another
foot or so expected for areas above 8000ft and less than 3 inches
for areas below 8000ft across the Sierra Madre and Snowy ranges. The
next precipitation chances look to come in the later half of next
week as a cold front brings upslope flow to the northern Laramie
range and interior higher elevations. This event looks to have
significantly less moisture to work with than the weekend event and
thus only a few inches are expected for the higher elevations and a
dusting across the front range and high plains.

- Wind

Guidance is coming into better agreement on Saturday with a potent
140kt+ jet streak impinging upon southeast Wyoming by Saturday
morning with the GFS on the high end of guidance forecasting a 60kt
700mb jet streak while the NAM and ECMWF keep it closer to 50-55kts.
Regardless this should be enough to see a few gusts over 55mph in
the northern Laramie Valley near Arlington. This should be a short
event as the jet washes out through the day but High Wind Warning
looks fairly likely given the in house guidance amongst other
sources. Looking ahead to early next week there continues to be a
strong signal for high winds given an increasing pressure gradient
but the magnitude will depend on the track of a shortwave across the
northern plains. The GFS and ECMWF still show differences in track
that are drastic enough to make or break this forecast but overall
the potential exists for a stronger than typical wind event that
would extend beyond just the traditional wind prone areas.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1030 AM MST Thu Dec 4 2025

Widely varying conditions today and tomorrow with MVFR to
briefly IFR conditions in the RWL area and high winds extending
east from there into the LAR region. Aside from RWL all sites
remaining VFR through the period through nearing MVFR towards
Friday afternoon as the system impacting the interior shifts
east bringing lower ceilings. Some winds shear for RWL and LAR
and for the southern NE panhandle sites of BFF and SNY. Overall
winds gusts outside the mtn sites 20-25kts and prevailing
directions from the WSW to NW through the period.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 6 AM MST Friday for WYZ106.
     High Wind Warning until noon MST Friday for WYZ110-116.
     Winter Storm Warning from 11 PM this evening to 5 AM MST
     Sunday for WYZ112-114.
NE...None.

&&

$$

SHORT TERM...MAC
LONG TERM...WFOCYS
AVIATION...TJT