204
FXUS65 KRIW 170401
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1001 PM MDT Thu Oct 16 2025

.KEY MESSAGES...

- Precipitation ends around midnight. Light mountain snow
  lingers through about sunrise Friday.

- Warmer and drier conditions on Friday.

- Saturday through early next week will remain unsettled with an additional
  system or two bringing precipitation chances to the area.

&&

.UPDATE...
Issued at 1242 PM MDT Thu Oct 16 2025

Forecast remains on track, with lower elevation rain and mountain
snow through tonight. Heaviest mountain snow occurs late morning
through this afternoon, impacting mountain passes and high elevation
roads. Precipitation chances end for most locations by about
midnight, with lingering snow over the mountains through Friday
morning. Precipitation chances and amounts have been adjusted with
latest model trends, but no notable changes were made with this
update.

&&

.DISCUSSION...
Issued at 434 AM MDT Thu Oct 16 2025

The forecast in the short term will continue to be dominated by a
highly amplified trough and associated upper low that is now moving
into southern Wyoming. Ongoing jet-induced showers and thunderstorms
will be bolstered by sunrise as the low moves farther northeastward
into central Wyoming. Colder air is concurrently moving east across
the state this morning. Precipitation is expected to become fairly
widespread by mid-morning, wrapping cyclonically around the low and
steadiest across central Wyoming and over any mountains.

Snow levels will drop to around or just under 7,000 ft this morning,
which could at least briefly bring light accumulations to elevated
surfaces across western Wyoming and the Green River Basin. Winter
Weather Advisories remain in effect for most of the mountains
through this evening. The Bighorns continue to be the exception,
with most of the accumulation there expected to be along the higher
peaks of the Cloud Peak Wilderness. Travel impacts due to snow
should remain limited to the mountain passes across the area.

Precipitation will begin to wane by sunset today as the low moves
into northeastern Wyoming and drier air pushes in behind it. Johnson
County and the eastern Bighorn Basin will likely hold on to
precipitation the latest before most of this activity comes to an
end by midnight. Light snow may continue overnight across the
mountains of northwestern Wyoming though with little to no
additional accumulation. Total liquid precipitation amounts through
the rest of this system will be highest along the track of the
low from northern Sweetwater County through Johnson County.
These areas will generally have around a 50 to 70 percent chance
of at least a quarter of an inch and a 30 to 50 percent chance
of at least a half inch.

Westerly wind will increase Friday morning in the wake of the system
as surface pressure decreases to our east. Temperatures will
moderate Friday afternoon and no precipitation is expected. Guidance
is then keying in on a glancing blow from a trough to our north
arriving Friday night. This should bring a cold front and a quick
shot of moisture through Saturday morning along and east of the
Continental Divide. By Saturday afternoon this feature should
already be east of the area, with ridging settling in behind it.
Accordingly, Sunday is favored to be warmer and drier. However,
guidance is showing yet another system arriving Sunday evening. This
one appears a little more substantial and may return more widespread
precipitation chances to the area early next week, including
mountain snow.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 958 PM MDT Thu Oct 16 2025

The main concern will be the potential for fog development tonight
into Friday morning. This will be highly dependent on where
skies clear and wind is light. KJAC and KWRL have the best
chance of fog development from about 10-14Z Friday morning. For
now have kept the TEMPO groups at the aforementioned terminals.
For KWRL there may be too much cloud cover overnight for fog
development. Other terminals that have a chance (15%) are KRIW
and KLND due to skies already clearing and light wind. Not a
high enough chance (15%) for any mentions in the TAFs at this
time. MVFR CIGS at KRKS should slowly lift tonight as the
weather system moves well to the east of the area.

Have added a PROB30 group at KCOD for -SHRA and MVFR conditions
starting at 05Z Sat as the next weather system begins to push in
from the north by that time. Rain chances will increase across
northern Wyoming Friday night, but rain showers will be scattered.
Wind will remain elevated at KCPR and KRKS through the TAF period.
KCPR will have a noticeable wind increase, with gusts of 25-30 knots
early Friday morning as the pressure gradient tightens ahead of the
approaching weather system. Most terminals will have a gusty wind
Friday afternoon. A cold front will bring a wind shift at KCOD
and KWRL late Friday evening, becoming northwesterly.

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.

&&

$$

UPDATE...Wittmann
DISCUSSION...Myers
AVIATION...Rowe