989
FXUS65 KRIW 020810
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
110 AM MST Tue Dec 2 2025

.KEY MESSAGES...

- Am approaching cold front will bring snow to western portions
  this morning. Blowing snow could make travel conditions
  difficult over Teton and Togwotee Passes this morning. Light
  snow will occur over areas east of the Divide tonight, as the
  cold front moves through the area.

- Strong gusty winds will occur over the Absaroka and Wind River
  Mountains and the Wind Corridor this morning. Gusts of 50 to
  55 mph will occur in the more wind prone locations. Areas of
  blowing snow will occur over portions of the Bighorn Basin and
  northern Johnson County tonight behind the cold front.

- Chances for snow will return starting Thursday night and
  continue into Saturday. Western portions of the CWA will have
  the best chances for snow during this time.

&&

.DISCUSSION...
Issued at 1254 AM MST Tue Dec 2 2025

The first round of snow has already passed over northwestern
portions, between 03Z and 06Z. There will be a lull for a few hours
before snow returns by 12Z this morning, as the main storm system
approaches from MT. Snow flurries will be possible through the rest
of the night east of the Divide. As snow redevelops over far
northwestern portions and the Bighorns, snow chances will increase
across western portions of the CWA through the morning hours and
continue through the day and evening. Snow will develop east of the
Divide after 00Z, as the cold front enters the area and progresses
southward. This area will be the focus for the snowfall tonight, as
snow ends across the west by 06Z (11pm). Forecasted snowfall amounts
have trended downward, with most locations east of the Divide being
an inch or less. A few orographically-favored locations look to get
2 to 3 inches, like the south side of Casper, Lander and Meeteetse.
2 to 3 inches is also forecasted in the Star Valley, due to
favorable dynamics. Locally higher amounts of 4 to 5 inches on the
east side of the valley cannot be ruled out. Otherwise, snowfall
amounts in the mountains will be highly variable ranging between 1
to 4 inches. The Tetons, Salt/Wyoming Ranges and the far north end
of the Bighorns will have the highest amounts of 4 to 6 inches. West
to northwest winds, with gusts of 35 to 45 mph, will continue over
the east slopes of the Absaroka and Wind River Mountains as well as
southern portions of Fremont and Natrona counties this morning and
through much of the day today. These conditions will occur at
Dubois, Cody and Clark as well. Gusts of 50 to 55 mph will also
occur along Hwy 258 on the south side of Casper. Gusts of 25 to 30
mph will then be common after 18Z across areas west of the Divide
and portions of the Wind River Basin. Northerly winds gusting 30 to
40 mph will occur over Johnson County and northern portions of the
Bighorn Basin after 22Z, as the cold front begins its southward
progression. Reductions in visibility due to blowing snow will be
brief, as the snowfall will be light tonight.

Snow will be ending across the area during the predawn hours
Wednesday morning, with a few locations of lingering snow through
the rest of the morning. Conditions will remain dry Wednesday night
and Thursday, temperatures moderating a few degrees on Thursday.
Details for the end of the week and into the weekend continue to
change. Models have trended toward a fast moving cold front moving
over the area Thursday night and exiting the area through Friday
morning. This system would bring another chance for widespread snow
east of the Divide and western portions. Chances for accumulating
snow over the western mountains continue to look good from Friday
afternoon into Saturday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 950 PM MST Mon Dec 1 2025

West of the Continental Divide...KJAC/KRKS/KPNA/KBPI Terminals

Snow already starting to pick up at KJAC this evening, and is
still expected to pass through in two waves during the next 24
hours. The first is now through around 09Z with TEMPO MVFR vis
and cigs. There will be a break the rest of the night into
Tuesday morning, with snow confined to nearby higher terrain.
The next wave still expected around 16Z, with a better
probability of lower cigs and vis reaching IFR ranges.
Likelihood of precip at KBPI/KPNA/KRKS remains low with this
system, with main impacts being lower cigs after 00Z/03. Gusty
winds at KRKS will continue well into the day Tuesday, with
frequent gusts near 35kts.

East of the Continental Divide...KCPR/KCOD/KRIW/KLND/KWRL Terminals

Cloud cover will remain confined to mid to higher level decks
through tomorrow morning. The second wave will come through east
of the Divide during the day Tuesday, with gradually lowering
cigs. Winds will shift from the north during the afternoon as
the cold front starts to push through. The main push will be
after 00Z/03, and will quickly bring lower cigs and -sn to these
sites. Have added a -sn/low vis line late in TAFs for this, but
timing is still not set in stone yet. Once the front does move
through, expect cigs to fall quickly to IFR/LIFR, with -sn
through the rest of the night.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM MST this evening for
WYZ012.

&&

$$

DISCUSSION...LaVoie
AVIATION...Straub