912
FXUS65 KCYS 171145
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
445 AM MST Mon Nov 17 2025

.KEY MESSAGES...

- A Pacific storm system will impact the area Monday with
  snow...rain...and cooler temperatures. High Wind Warning
  remains in effect for the wind prone areas of southeast
  Wyoming.

- Locally heavy mountain snowfall will continue today with a
  Winter Weather Advisory in effect until late this evening.

- Gradual cooling trend expected after Tuesday with the next
  chance of rain and/or snow Thursday and Friday.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 245 AM MST Mon Nov 17 2025

Only made a few tweaks to the forecast for today with most
things appearing on track early this morning. A quick look at
the SNOTEL sites across the mountains show a quick 2 to 5 inches
of snow, mainly over the Sierra Madre Range, fell late Sunday
evening with the first band of precipitation associated with the
cold front. We`re in a brief lull right now as the upper level
low is tracking along the Wyoming/Colorado border at this hour.
Once it slowly ejects east later this morning, upslope snow
will start with snowfall rates increasing through the day.
Winter Weather Advisory looks good and not we`re not expecting
to upgrade to a Winter Storm Warning at this time. Nudged
snowfall totals a little lower based on current observations and
precip totals along the area. Otherwise, the previous shift
adjusted the valid time of the High Wind Warning to include late
last night and early this morning. This has worked out well
since a few sites near Arlington have gusted over 58 MPH so far.

Otherwise, shower activity across the eastern plains early this
morning has had some embedded thunder associated with it. Lightning
detection is picking up mostly cloud pulses, but a few CG
strikes have been detected over far northern Colorado and the
southern Nebraska Panhandle. Added isolated thunder to the
forecast up until sunrise.

Once again, the biggest forecast uncertainty continues to be
timing of the strongest winds. Models have trended a little
later with the strongest winds across the I-80 Summit and
foothills...and potentially into Cheyenne and the general
vicinity. Current models indicate high winds into the evening
hours to late evening hours Monday. Adjusted wind timing a bit
to account for this, but thankfully the High Wind Warning is
good until 11 PM tonight. Before this evening, not sure if the
I-80 Summit will see too much wind with how slow the upper level
low is moving so far this morning. Could see gusts up to 70 MPH
on the backside of low with increasing low to midlevel winds and
strong pressure gradient along the Front Range.

For tonight, increased POP through late this evening with high
res models showing the system and associated precipitation
taking their timing moving out of the area. This may result in
some additional snowfall amounts across the mountains, but not
expecting anything more than a few inches. Rain is still
expected below 7000 feet, so this additional rain shouldn`t be a
big deal across far eastern Wyoming and western Nebraska. Since
the system moves out of the area slowly, increased low
temperatures a few degrees due to lingering cloud cover.

Models in good agreement for Tuesday, showing the upper level
low finally ejecting east and becoming an open wave trough
across the Great Plains. A slight warming trend is expected with
partly sunny skies and dry weather. Temperatures during the day
should peak in the upper 40s to upper 50s for most of the area,
and low 60s possible for the lower elevations of western
Nebraska.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...

Update...
Issued at 150 AM MST Mon Nov 17 2025

Previous long range forecast remains mostly on track, but
ensemble guidance is hinting towards a more northward track of
the storm system Thursday and Friday. Around 25% to 40% of the
ensemble members, from both the GEFS and ENS, show a decent
chance of 0.50 of an inch or higher QPF and warning snow amounts
above 5500 feet from Laramie to Cheyenne with higher QPF amounts
over the central/southern Nebraska panhandle...which should
mostly be rain or rain/snow mix. Agree with the previous shift`s
assessment and will keep the higher POP in the forecast late
Thursday and into Friday. Deterministic models have trended a
bit further north as well, especially the 00z Canadian. If this
trend continues, may need to lower max and min temperatures both
days. Will continue to monitor this storm closely through the
week.


Previous Discussion...
Issued at 516 PM MST Sun Nov 16 2025

The long term forecast looks rather unremarkable as the pattern
takes a shift towards more seasonable weather. Cooler temperatures
are expected behind Sunday night`s cold front, although temperatures
will still remain normal to slightly above average for this time of
year. Tuesday and Wednesday will feature warmer high
temperatures than Monday as weak ridging ushers in warmer air
aloft. Highs will be in the 40s and 50s, with some 60s
potentially sneaking into the Nebraska panhandle. For the most
part, subsidence under the ridge will keep precipitation at bay,
however, cannot rule out some light mountain snow from
increased mid-level moisture and orographic lift.

Heading into the end of the work week, a potential storm system
could impact the CWA. However, it appears models have trended this
system further south so that impacts to the CWA will be quite
minimal. Both the deterministic GFS and ECMWF as well as their
ensemble low clusters show the surface low developing pretty far
south in southeast Colorado/Oklahoma panhandle. Agreement seems
to be pretty good on the surface low development and track,
which will keep most of the precipitation out of the CWA. As a
result, lowered PoPs on Thursday and Friday below NBM guidance.
Temperatures will likely be colder both days as the trough
swings through the Rockies. However, the ECMWF advertises colder
temperatures than the GFS with colder air aloft.

Once this system moves out, temperatures look to warm back up over
the weekend, however models are in disagreement regarding whether or
not there will be precipitation.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 445 AM MST Mon Nov 17 2025

A potent upper level storm system is forecast to move through the
area today and exit to the east by late this evening. Periods of
rain, with snow above 7000 feet, are expected into this evening
across southeast Wyoming and western Nebraska...especially north of
Interstate 80.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail through this
afternoon with periods of MVFR conditions due to rain or rain/snow
mix. Expect KLAR, KCYS, and KSNY to stay primarily VFR with lower
precip chances compared to the rest of the area. Shower activity
will become more widespread around KRWL this morning with brief IFR
conditions in snow possible. All terminals will see increasing winds
with gusts up to 40 knots possible by this afternoon and this
evening. A few rounds of rain shower expected over the western
Nebraska terminals this morning and then again late this afternoon
through this evening. MVFR CIGS and even some patchy fog are looking
more likely for KCDR and KAIA after 01z Tuesday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...High Wind Warning until 11 PM MST this evening for WYZ110.
     Winter Weather Advisory until 8 PM MST this evening for WYZ112-
     114.
     High Wind Warning from 5 AM early this morning to 11 PM MST
     this evening for WYZ116-117.

NE...None.

&&

$$

SHORT TERM...TJT
LONG TERM...SF
AVIATION...TJT