314
FXUS65 KRIW 021211
AFDRIW

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

.KEY MESSAGES...

- An 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 /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 400 AM MST Tue Dec 2 2025

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

An approaching cold front will bring snow chances and reduced flight
conditions to all terminals this TAF period. The first terminal to
experience impacts will be KJAC around 16Z with MVFR flight
conditions. Confidence is high that there will be a period of IFR
flight conditions with a heavier band of snow during the afternoon
hours as the cold front begins to push through. KPNA would be the
next terminal to have snow chances (30%); however, confidence is
much lower in direct snow impacts so a PROB30 group reflects the
chances. KBPI has similar direct snow chances (30%) late in the TAF
period. Regardless of snow directly impacting the terminals,
confidence is high in MVFR ceilings at both KPNA and KBPI as the
cold front moves through. KRKS is forecast to have MVFR flight
conditions and direct snow impacts with the cold front passage.
Mountain obscuration can be expected at all terminals.

KRKS is expected to be gusty ahead of the cold front with
frequent gusts between 25kts and 35kts. Winds at KJAC, KBPI, and
KPNA generally remain around or less than 10kts.

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

An approaching cold front will bring snow chances and reduced flight
conditions to all terminals after 00Z. Ahead of the cold front/before
00Z, VFR flight conditions are forecast with gusty winds at KCOD,
KCPR, and KRIW. Post frontal gusts are expected at KCOD. As the cold
front approaches, low VFR to MVFR ceilings will begin to filter into
each terminal. Where confidence in MVFR ceilings is between 20-30%,
a SCT025 or SCT030 cloud deck has been added. Confidence is high in
MVFR and/or IFR flight conditions and light to moderate snow at each
terminal with and behind the cold front. Mountain obscuration can be
expected after 00Z.

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...Gerhardt