433
FXUS65 KRIW 011105
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
405 AM MST Mon Dec 1 2025

.KEY MESSAGES...

- Isolated areas of fog/low clouds in the Upper Green River
  Basin this morning and possibly the Jackson/Star Valleys.

- Monday will be dry and high temperatures several degrees
  warmer. Breezy afternoon westerly wind 20 to 30 mph occurs
  over southwest Wyoming into Natrona County as well as near
  Dubois and Cody.

- The next storm system arrives in western Wyoming Monday night
  into Tuesday. Light snow gradually spreads east of the
  Continental Divide Tuesday evening and persists through the
  Wednesday morning commute.

- Northwest flow aloft favors additional light snow in the
  western and northern mountains late in the week. Temperatures
  across the region remain seasonal heading into next weekend.

&&

.DISCUSSION...
Issued at 122 AM MST Mon Dec 1 2025

Snow ended across the area earlier Sunday evening. Apart from a few
high clouds, skies will be clear this morning for most of the area.
Some low clouds/fog could push into the Star Valley in the next few
hours, as well as areas along Hwy 28 near Farson. Conditions will
remain dry today, with temperatures about 5 to 10 degrees warmer.
Some locations will be 15 to 20 degrees warmer from Sunday, due to
highs in the teens yesterday. Winds will be a bit breezy today, with
gusts of 25 to 30 mph occurring across southern portions and Natrona
County. Areas near Dubois and Cody will also be breezy, with locally
higher gusts around 35 mph.

Another storm system will quickly make its to the CWA from the north
this evening, with snow developing over northwestern portions by 04Z
Tuesday and spreading southward through the rest of the night
tonight. Winds will increase over the east slopes of the Absaroka
and Wind River Mountains irt this latest (third) storm system. West
to northwest winds, with gusts of 35 to 45 mph, will develop by 06Z
and continue through much of the day Tuesday. These conditions will
occur at Dubois, Cody and Clark as well. These winds will then
spread across southern portions of Fremont and Natrona counties by
12Z. Gusts of 50 to 55 mph will be possible 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. Isolated snow showers will also occur across areas east
of the Divide through the afternoon and become more widespread in
the evening, as the associated cold front makes its way southward.
This system will be a bit slower than the previous two, with light
snow continuing through Wednesday morning. Snowfall amounts of 1 to
2 inches is expected over central portions and the western valleys,
with 3 to 6 inches in the mountains.

Snow will end across the area through the rest of the morning
Wednesday, as high pressure builds into the area from the north
through the afternoon. Conditions will remain dry Wednesday night
and Thursday, with a chance for snow over northwestern portions due
to upslope flow from another incoming system on Friday. Impacts from
this storm will be widespread once again, however it will track
further north so snowfall amounts look to stay on the light side
again. Periods of snow look possible Friday and Saturday across
western portions, due to the semi-consistent upslope flow. Exact
details will become clearer in the next few days as we progress
through the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 403 AM MST Mon Dec 1 2025

At KPNA, IFR flight conditions should begin to improve between 14Z-
16Z this morning. Then, VFR flight conditions are forecast most of
the TAF period all West of the Divide terminals. Moisture begins to
filter into the region after 00Z Tuesday, resulting in increasing
cloud cover and occasional mountain obscuration. There is a 20%
chance of MVFR ceilings at KJAC and KPNA after 08Z Tuesday and these
chances are reflected in a prevailing SCT030 group. The disturbance
aloft associated with the increased moisture will reach western
Wyoming/KJAC late in the period, bringing a 30% chance of snow
showers at KJAC between 06Z-12Z Tuesday. Chances at KPNA, KBPI, and
KRKS are between 10%-20%, so there is no mention in TAF at this
time. MVFR flight conditions could accompany any snow showers.

At KRKS, KPNA, and KBPI, winds increase between 17Z and 20Z with
gusts between 20-30kts and continue through the evening. Expect KRKS
to be the gustiest terminal. At KJAC, expect winds to become gusty
as the disturbance aloft approaches after 06Z Tuesday.

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

VFR flight conditions are forecast this TAF period. Moisture begins
to filter into the region after 00Z Tuesday, resulting in increasing
mid level cloud cover and occasional mountain top obscuration. After
16Z, winds increase with gusts around 25kts at KCPR until 00Z
Tuesday when gusts subside. KCOD is forecast to become gusty after
02Z Tuesday as a disturbance aloft begins to shift into the region.
There is a 20% chance in gusty west-northwest winds between 20-30kts
at KRIW after 07Z Tuesday, however, given these low chances there is
no mention in TAF at this time.

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 from 11 PM this evening to 11 PM MST
Tuesday for WYZ012.

&&

$$

DISCUSSION...LaVoie
AVIATION...Gerhardt