615
FXUS65 KCYS 092212
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
312 PM MST Tue Dec 9 2025

.KEY MESSAGES...

- The long duration wind event continues, with wind gusts
  expected to peak Tuesday. While some breaks or lulls will
  occur, high winds will be a concern every day through
  Saturday.

- A cold front will bring a banded rain and snow showers late
  Tuesday afternoon through the evening. This will also bring a
  brief reprieve from the wind into Wednesday morning.

- High winds return Wednesday with another round of High Wind
  Watches in place for the southeast Wyoming wind prones and
  wind prone adjacent areas.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 307 PM MST Tue Dec 9 2025

High Wind Warnings are performing excellent with most zones
consistently verifying throughout the day. Peak gusts have occurred
in the usual wind prones with frequent gusts over 80 MPH. Wind prone
adjacent areas have see gusts in the 70s and the high plains have
seen 50 to 60+ MPH winds. High winds will continue through the
afternoon hours as steep MSLP and height gradients keep winds aloft
above 55 kts. A cold front moving into the CWA this evening will
effectively shut off the winds as MSLP gradients weaken and winds
turn more northwesterly. This break, however, will be short-lived as
the next round of high winds is progged to start Wednesday morning.

The incoming cold front will likely bring some precipitation to the
CWA this evening and overnight. Based off Hi-Res guidance,
precipitation looks scattered and almost convective in nature as
weak pockets of instability exist. Given the instability and
lingering strong winds, squall-like showers could be possible,
especially overnight when precipitation is more likely to be snow.
Some light snowfall could be possible for the high valleys west of
the Laramie Range, but accumulations should generally stay under an
inch. Winter Weather Advisories are in place for the Snowy and
Sierra Madre this afternoon through Wednesday morning as the front
will bring good mid-level moisture and upslope flow to the high
terrain. Accumulations will be between 6 and 12 inches with the
highest peaks expected to see more.

High winds will return to the area once again on Wednesday as the
the 250 mb jet streak continues to linger over the region. A series
of weak upper-level disturbances will traverse the CWA throughout
the day, allowing a surface trough to develop in lee of the Laramie
Range. This surface trough will cause MSLP and height gradients
along and west of the Laramie Range to steepen, increasing winds
aloft. Luckily, the parameters for this event do not look as
severe or as widespread as the event currently ongoing. However,
the wind prone locations can still expect to see gusts over 70
MPH and wind prone adjacent areas could see gusts over 60 MPH.
Winds will gradually begin to increase throughout the morning
hours, with mixing helping to get some of these winds down to
the surface during the afternoon. For now, decided to leave the
High Wind Watches in place for this secondary event. Upgrades to
these Watches are likely, however did not want to upgrade quite
yet with High Wind Warnings currently in place for the ongoing
event. High Wind Watches are in place for the usual southeast
Wyoming wind prones and wind prone adjacent areas. High winds
are likely to continue into Wednesday night as gradients remain
steep and winds aloft remain strong. Subsidence should be more
than sufficient to get these winds down to the surface.

It comes as no surprise that high winds are likely to continue
through the day Thursday. Gradients remain tight with roughly a 15
mb gradient expected over the CWA. This will allow winds aloft to
remain in the 55 to 65 kt range with strong downward omegas. The
biggest change to the forecast package came with the modification of
ending times for this second high wind event. The GFS keeps the
strong winds around longer than previous runs, so decided to
extended the High Wind Watches through Thursday evening. Besides
the never ending winds, Thursday will be quite warm thanks to a
warm front that will move across the region late Wednesday
night. Temperatures east of the Laramie Range will make it into
the upper 50s and 60s! This will put temperatures about 20
degrees above average for mid-December!

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 307 PM MST Tue Dec 9 2025

As this high wind event finally begins to tail off into the weekend
the wind prones will likely still need a warning for the better part
of Friday and possibly Saturday as well. With the active jet once
again impinging upon the area and the ridge getting nudged back
west, 50-55+ kt 700mb flow will once again become entrenched over
the southeast WY plateau. Given this low level wind max and
pressure/height gradients remaining favorable, high winds are likely
to persist into the early weekend (midday Saturday) in the wind
prone areas of I-80 and I-25 near Bordeaux. With confidence still
not quite there in terms of start/end timing combined with the
warning soup that is the preceding few days will hold off on any
additional headlines for now to try and avoid any confusion.

Beyond what seems to be the unending high winds is a good downslope
airmass which look to take hold (really starting today) and not let
go well into next week as highs frequently climb into the 50s near
the Colorado stateline for Friday/Saturday, and for all areas east
of I-25 Sunday and beyond into the middle half of next week. Look
forward to this weekend for some calmer December weather.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1025 AM MST Tue Dec 9 2025

MVFR cigs may sneak into RWL and LAR this afternoon into early
tonight but the main story remains the anomalous high wind
event. Gusts upwards of 60-70kts in the Wyoming terminals and
50kts in the Nebraska sites will linger through the evening with
gusts dropping below 30kts for all sites by or around 12z. Much
more tranquil for most tomorrow as winds turn SW outside the
mountains and sustained winds under 15 mph. A few snow showers
are possible mainly for Wyoming sites this afternoon as well and
could briefly drop vis to 4-6sm in any heavier showers.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 8 PM MST this evening for WYZ101-102-
     104-105-108-109-119.
     High Wind Watch from Wednesday morning through Thursday
     afternoon for WYZ101-107.
     High Wind Warning until midnight MST tonight for WYZ103-106-
     107-113>115-117-118.
     High Wind Watch from late tonight through Thursday afternoon
     for WYZ104-109.
     High Wind Watch from Wednesday morning through Thursday
     afternoon for WYZ105-113-115.
     High Wind Warning from 9 AM Wednesday to midnight MST Thursday
     night for WYZ106-117.
     High Wind Warning until 5 AM MST Friday for WYZ110-116.
     Winter Weather Advisory until 11 AM MST Wednesday for WYZ112-
     114.
     High Wind Watch from Wednesday morning through Thursday
     evening for WYZ118.
NE...High Wind Warning until 8 PM MST this evening for NEZ002-003-
     019>021-054-055-095-096.

&&

$$

SHORT TERM...SF
LONG TERM...WFOCYS
AVIATION...WFOCYS