292
FXUS65 KRIW 300906
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
206 AM MST Sun Nov 30 2025

.KEY MESSAGES...

- A weather system will bring mainly light snow to southern and
  southwestern Wyoming today and this evening.

- Tomorrow will be a dry and somewhat milder day.

- A couple of systems will bring additional chances for snow on
  Tuesday and the end of the week, although details are still
  fairly uncertain.

&&

.DISCUSSION...
Issued at 201 AM MST Sun Nov 30 2025

It is a quiet but rather cold night here at the humble Riverton
weather abode, some locations have their coldest temperatures so far
this season. Things will turn a bit more active again today though.

The culprit for this is a weak area of low pressure that will drop
across Idaho and then into Utah and Colorado. This does not look
like a big storm for us given that the system is fairly moisture
starved and the best dynamics will remain to the south of Wyoming.
As a result, snowfall amounts look relatively small. Ensemble
guidance gives at most a 1 in 3 chance of 2 inches or more in the
southern Star Valley and southern Lincoln Counties, with most other
lower locations having at most a 1 in 2 chance of an inch of snow.
Nevertheless, there could be some impacts on a busy travel day at
the end of the Thanksgiving Day weekend, including Interstate 80.
Not enough for an advisory though.  The highest amounts will occur
in the Salt and Wyoming Ranges but even here there is only at most a
1 in 3 chance of 4 inches across the higher peaks with a near
zero chance of 6 inches. As for elsewhere, a few snow showers
could jump the divide but any amounts East of the Divide would
likely be slim to none. The time of most impact would be from
around 9 am to 4 pm, with all snow ending by midnight tonight as
the system moves away to the south and east. Otherwise, expect
another cold day with temperatures averaging 5 to 10 degrees
below normal.

High pressure should bring a dry start to the work week on Monday
with temperatures climbing closer to seasonal normals as our air
mass modifies a bit. There will be a gusty wind in the southwestern
wind corridor from Rock Springs through Casper ahead of the next
weather system. This system will bring impacts for Tuesday into
Tuesday night. Most areas have the potential for more accumulating
snow. Ensemble guidance gives much of northern and central Wyoming
at least a 1 out of 3 chance of 2 inches of snow or more, although
again this does not look like a major storm, with the chance of 6
inches or more generally less than 1 out of 4 except in the
mountains. The problem with this system is that there are a lot of
moving parts and guidance still has a rather substantial spread on
most aspects including timing and placement of the heavier snow. So,
confidence is fairly high there will be some snow, details are
still uncertain. Then, after a dry Thursday, another system may
approach for the end of the week and next weekend. Like the
previous system, there is still a decent spread in guidance and
details are difficult to resolve this far out. Temperatures
should average fairly close to seasonal normals, with the
coolest temperatures expected Wednesday behind the next cold
front. However, no arctic outbreaks are expected for the next
week.
&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 955 PM MST Sat Nov 29 2025

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

A quick-moving shortwave will rotate across southwest Wyoming with
the greatest impacts during the day Sunday. VFR conditions begin to
deteriorate between 13Z-16Z/Sunday with IFR/MVFR developing around
16Z at KBPI/KPNA and 18Z at KRKS. The north end of this wave wraps
around to the vicinity of KJAC. Current trends keep MVFR to the
south of KJAC, so only have PROB30 low-end VFR from 15Z-19Z/
Sunday. Conditions slowly improve from north-to-south between
21Z-24Z/Sunday as the wave rotates out of the region. VFR follows
at all terminals, although the Sunday night potential for fog
will need to be monitored at KBPI/KPNA. Mountains frequently
obscured 15Z-23Z/Sunday, with mountain top obscurations
throughout the period.

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

Impacts from a quick-hitting shortwave moving through southwest
Wyoming will be limited to lower-end VFR ceilings in the central
basins during the midday hours Sunday. There could be a few snow
showers spill over the Divide near KLND early Sunday afternoon, but
the chance is at best 30 percent. Opted to leave out PROB30 for the
time being. Otherwise, VFR conditions reign through the period.
Cloud cover dissipates from north-to-south from late Sunday
afternoon into the evening hours. Mountain top obscurations occur
along the Continental Divide between 12Z/Sunday and 03Z/Monday.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Hattings
AVIATION...CNJ