199
FXUS65 KRIW 031710
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1010 AM MST Wed Dec 3 2025

.KEY MESSAGES...

- Snow ending across the area this morning. Areas of blowing
  snow possible over Interstate 80 through the morning, as winds
  decrease by midday.

- Winds gusts of 35 to 50 mph will be possible late tonight
  north of Cody and the Upper Wind River Basin.

- Areas of fog will develop over portions of Yellowstone NP
  tonight, and possibly spreading into northern portions of the
  Jackson Valley.

- Periods of snow will begin over northwestern portions Thursday
  afternoon and spread to far western portions Thursday night. A
  break in the snow is possible Friday afternoon, before
  starting again Friday night and ending late Saturday night.
  Snowfall amounts of 1 to 2 feet are possible in the western
  mountains and amounts approaching 12 inches in the
  Jackson/Star Valleys from Thursday afternoon to early Sunday
  morning.

&&

.DISCUSSION...
Issued at 129 AM MST Wed Dec 3 2025

Snow continues to fall over central portions shortly after midnight
this morning, as it progresses southward. This snow will end over
the next few hours as drier air begins to settle into the area from
the north. Snow will primarily be over before sunrise this morning,
but a flurry or two cannot be ruled out through the rest of the
morning. Wind gusts of 30 to 40 mph will occur across Sweetwater and
southern Lincoln counties this morning, as the cold front continues
to track across these areas. Blowing snow will be a concern for the
morning commute across I-80, US-191 and South Pass/Hwy 28. These
winds will decrease through the morning after sunrise, with light
winds across the CWA today. Temperatures will be 5 to 15 degrees
colder today, as clouds gradually scatter out through the day.
Needless to say, it will be cold again tonight with lows in the
single digits and teens across the area. Fog will be possible over
Yellowstone and could infiltrate into the Jackson Valley from the
north like it did Monday morning. Gusty winds will develop tonight
over the east slopes of the Absaroka and Bighorn Mountains after
midnight, due to a tightening 700mb temperatures gradient. Gusts of
30 to 40 mph will occur, with locally higher gusts around 50 mph
near Clark. Similar winds with gusts of 25 to 35 mph will occur near
Dubois, Crowheart and the Casper area. These winds will continue
through the rest of the morning Thursday.

A large ridge over the EPAC and a Hudson Bay upper low will remain
in place through the rest of the week and be the primary drivers for
our weather for the next several days. A northwest flow pattern will
be in place over the region as a result. The PFJ will round the top
of the ridge tonight into Thursday, bringing the next surge of
Pacific moisture. This will bring light snow to northwestern
portions during the day, with increasing chances over far western
portions Thursday night. This will be the start of a multi-day snow
event for western portions of the CWA. A break in the snow looks to
occur Friday afternoon, before the next round quickly returns by
Friday evening. There is a good chance for steady snow to then occur
across the west from Friday night to early Sunday morning. Initial
snowfall amounts (from Thursday afternoon to Saturday night) range
between 1 to 2 feet in the western mountains and 8 to 12 inches in
the Jackson and Star Valleys. Again, this will be spread out over a
3-day period with the heaviest snowfall occurring Friday night.
Details for areas east of the Divide and southern portions are not
as clear. There is a chance for light snow over these areas Thursday
night and Friday night, but confidence is low for any real impacts
at this point. However, gusty winds do look likely especially
between Kemmerer and Casper. Gusts of 25 to 35 mph Thursday
afternoon and evening and similar speeds returning Friday afternoon.
Winds of 30 to 45 mph are possible Friday night, as the stronger
storm system moves over through the area. The east slopes of the
Absaroka, Bighorn and Wind River Mountains will have similar
conditions. The potential for high winds (wind gusts 60+ mph) will
have to be monitored, as models are forecasting 700mb winds of 50+ kt
occurring over southern portions, and areas east of the Divide (the
Cody Foothills, the Wind River Basin, and Johnson/Natrona counties).

Additional snow chances over northwestern portions will be possible
Sunday through Tuesday, as the ridge flattens. The pattern looks to
remain active next week and are making up for the warm and
relatively quiet November.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1009 AM MST Wed Dec 3 2025

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

Mid-level clouds should clear through the day, with VFR conditions
through the period. Winds will be relatively light and diurnally
driven today into tonight. Clouds begin to increase late tonight and
Thursday morning ahead of the next weather system. Current models
hold off snow chances until the very end, or after, the period. At
KJAC, a few models show snow chances arriving as early as late
Thursday morning, but the consensus is until at least 21Z, where
there is a PROB30 group. Chances increase further after the period.

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

VFR conditions prevail through the period as low to mid-level clouds
thin through the early afternoon. Winds remain relatively light and
diurnally driven through this evening. An approaching weather
system brings increasing winds and mid-to-high-level clouds starting
tonight. Strongest winds will initially be seen over the mountains,
so wind shear is possible at KCOD starting around 02Z. Elsewhere,
winds increase towards the end of the period or shortly after.

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...
None.

&&

$$

DISCUSSION...LaVoie
AVIATION...Wittmann