899
FXUS65 KRIW 231059
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
359 AM MST Mon Dec 23 2024

.KEY MESSAGES...

- Light snow continues across the west through Monday afternoon.
  Snowfall rates increase slightly this morning. Winter travel
  conditions expected, especially over mountains passes.

- Another system arrives Tuesday night, bringing light snow
  chances to western portions of the forecast area on Christmas.

&&

.DISCUSSION...
Issued at 1216 AM MST Mon Dec 23 2024

A weak, elongated trough will approach the Cowboy State today,
bringing another round of light to moderate snow to the western
mountains through the day. Snowfall amounts will be highest over the
Tetons and the Pitchstone Plateau in Yellowstone NP, with 8 to 12
inches expected. Locally higher amounts around 16 inches will occur
on the higher peaks. Lesser amounts of 4 to 6 inches is expected
over the western mountains, with 2 to 4 inches on Togwotee Pass.
Conditions will remain dry with slightly above normal temperatures
east of the Divide. Winds will be gusty across the south, including
the Casper area, with gusts of 25 to 30 mph.

Snow will end later this evening, as a ridge transitions over the
region. Dry conditions and above normal temperatures (at least east
of the Divide) will continue. Gusty winds will be confined to the
Wind Corridor, with gusts of 25 to 35 mph.

The odds for a White Christmas is not looking good for much of the
forecast area. The closed low that has been forecasted for the last
several days remains on track to dive southward over the Four
Corners region Tuesday night into Christmas Day. However, a trough
that is in phase with the low will move over the Northern Rockies.
This will bring light snow to western portions late Tuesday night
and through Christmas morning. This could even include Green
River/Rock Springs. Amounts will generally stay under an inch, with
the mountains possibly picking up 2 inches.

Conditions will remain relatively quiet Thursday and Friday, with
light snow remaining possible over the western mountains. A more
active pattern looks to develop by the weekend, with snow continuing
over the west and gusty winds for much of the area.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 357 AM MST Mon Dec 23 2024

West of the Divide (KBPI, KJAC, KPNA, and KRKS) Terminals:

MVFR and IFR flight conditions are expected at KJAC this TAF period.
A weather system moving into western Wyoming will bring light snow
showers to the Jackson area with accompanying lowering ceilings and
visibilities. Expect IFR visibilities in any heavier snow showers
that impact the terminal. Light snow showers should taper off after
03Z with ceilings rising by 06Z; however there is a 30% chance in
ceilings remaining MVFR after 06Z. At KBPI and KPNA, fog development
has been slower to develop than originally forecast and confidence
in its development is decreasing. That being said, there is
confidence (around 70%) in MVFR ceilings at KPNA during the day
today due to afternoon light snow chances, however MVFR
ceilings due to light snow at KBPI cannot be ruled out.

East of the Divide (KCOD, KCPR, KLND, KRIW, and KWRL) Terminals:

Otherwise all other terminals can expect dry and VFR flight
conditions through the TAF period. At KCOD, KCPR, and KRKS, gusty
winds around 20kts are forecast today. Gusty winds at KRKS and KCPR
will diminish between 06-08Z, whereas KCOD can expect winds to
decrease after sunset and increase again around 08Z.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 7 PM MST this evening for WYZ012.

&&

$$

DISCUSSION...LaVoie
AVIATION...Gerhardt