671
FXUS65 KCYS 302240
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
340 PM MST Sun Nov 30 2025

.KEY MESSAGES...

- A winter weather advisory is in effect for the Sierra Madre
  and Snowy mountains for snow accumulations up to 10 inches.

- A High Wind Watch has been issued for the wind prone areas of
  southeast Wyoming beginning Monday evening.

- Long term remains active with multiple systems promoting
  prolonged periods of high winds alongside mountain snow and
  chances of lower elevation snow as well.

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

&&

.SHORT TERM /THROUGH TUESDAY MORNING/...
Issued at 339 PM MST Sun Nov 30 2025

Mid-level water vapor shows the low tracking farther north than the
models had it yesterday. Recent model runs have severely decreased
QPF and snow accumulations. A weighted blend of old grids/NBM/NAM12
was used to retain advisory level snow accumulations for the
mountains but also add in some light snow accumulations for almost
everywhere east of I-25. As this system pushes east-southeast, the
synoptic forcing from the low passing over Southeast Wyoming should
be enough for light stratiform snow over the next 12 hours. While
accumulations wont be anything substantial accumulation`s of a few
tenths can`t be ruled out. There is also a little bit more moisture
than what the global and hi-res models are advecting in. Surface
dewpoints and RH levels are showing up a little higher than what the
models are forecasting. So there should be a sufficient amount
available to utilize that greater synoptic forcing to carry snow
production outside of the mountains. As this system rides the CO/WY
border it will drag cold dry air down from Canada abruptly ending
the light snowfall early Monday morning. A 700mb jet starts to
develop Monday afternoon causing the wind gusts to increase. Most of
the models have the jet increasing between 60 to 65kts by 06z or
midnight Monday going into Tuesday. Over the past couple runs the
global omega fields have been steadily increasing the subsident flow
over our wind prones concurrently with the increasing 700mb jet. Our
in-house guidance still maintains high confidence (80-90% probs) of
reaching high wind criteria by 00z Monday for the Arlington area.
However, the timing of jet intensification provided by the models is
a little delayed compared to our in-house guidance. Given there is a
little bit more time before headline decisions have to be made. So,
the watch was continued with no alterations to the timing.


&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 339 PM MST Sun Nov 30 2025

Long term remains active thanks to multiple systems bringing
rounds of precipitation alongside long durations of high winds,
with temperatures steadily warming during the later part of the
week to bring us back to near normal by the weekend.

The long term starts on Tuesday as an upper level trough will
sweep down the western US and will deepen into a near cutoff low,
with the strongest part of the system remaining well to the
south as this feature moves across the Four Corners area. But
then moving into the weekend, a weak ridge will try and take
over, but will be flattened by a quick moving trough into
Saturday. Under this pattern, we`ll see our first round of high
winds beginning just before the long term on Monday and
continuing into Tuesday afternoon, weakening thereafter. A high
wind watch is already out through 03Z Wednesday for our usual
wind prone locations, and we will likely see that upgraded
within the next 24 hours as models have remained consistent on
700mb winds in the 60-70 knot range, favorable downward omegas,
and strong, favorable pressure gradients across the area. In
house guidance continues to produce a 70-80% probability of high
winds as well, leading to very high confidence. Meanwhile a few
models have shown some increased QPF which would lead to higher
snowfall, but the majority of ensembles and the NBM are keeping
QPF in the mountains and to our south, so the expectation
remains we`ll see amounts high enough to warrant products, at
least advisories, in the mountains, with around 1-3 inches in
the lower terrain thanks to shadowing effects.

Moving into Wednesday and Thursday, both days should be
relatively calm and dry as the ridge tries to build in, but our
winds will once again begin increasing on Thursday in response
to the next approaching system as pressure gradients tighten and
the 700mb jet begins to re-establish and remain firmly planted
over the CWA through the weekend. In house guidance continues to
highlight this period and with such consistency there is
moderate to high confidence in a multi-day high wind event once
again for our wind prone regions. Meanwhile models expect that
this flow should allow for more chances of mountain snowfall
with some of this able to spill over into the adjacent high
plains, but once again shadowing effects are likely going to
limit how much accumulation we can produce outside of the high
terrain. Finally our temperatures start off near normal on
Tuesday with highs in the 30`s to 40`s, dropping notably on
Wednesday thanks to the passage of the front with the first
system and highs not making it out of freezing, but as the
ridge tries to take control through the weekend a modest warming
trend should bring us back to the 30`s and 40`s by Saturday.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1053 AM MST Sun Nov 30 2025

A mix of all flight categories expected as a system brings
widespread snow showers to the region today through tonight. All
sites are expected to have nearby snow showers if not moving
directly over, though airports that are most likely to see
precipitation are all WY terminals as well as KSNY. These snow
showers could cause VIS and/or CIGs to drop to IFR or even LIFR
status at times. Winds will also be breezy as this activity
moves through, with speeds 10-25 knots expected. As we move into
this evening and overnight into tomorrow, winds should lessen
and precipitation should exit the region, with skies lifting and
clearing as well. Winds will begin to pick back up tomorrow into
the afternoon.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from Monday evening through Tuesday morning
     for WYZ106-116-117.
     High Wind Watch from Monday afternoon through Tuesday evening
     for WYZ110.
     Winter Weather Advisory until 5 AM MST Monday for WYZ112-114.
NE...None.

&&

$$

SHORT TERM...MM
LONG TERM...CG
AVIATION...CG