690
FXUS65 KRIW 302033
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
133 PM MST Sun Nov 30 2025

.KEY MESSAGES...

- A quick-moving weather system brings light snow across
  southern Wyoming through this evening. Minor winter travel
  conditions for portions of I-80 through about 5pm MST.

- Monday is dry, with high temperatures a few degrees warmer.
  Breezy afternoon winds 20 to 30 mph occur over western Wyoming
  and into Natrona County.

- Multiple weak weather systems are expected this week, bringing
  light snow chances and keeping temperatures cool to seasonal.
  The best chance for widespread light snow comes Tuesday and
  Tuesday night.

&&

.UPDATE...
Issued at 1119 AM MST Sun Nov 30 2025

No major changes with today`s forecast. A quick-moving weather
system brings light snow to southern Wyoming through this evening.
It seems to be slightly further south than previous models had,
resulting in snow amounts coming down ever so slightly, with chances
decreasing across Jackson Valley and the northern Green River Basin.
The main impacts remain to be for any travel along I-80 and southern
Lincoln County, were some snow and breezy winds (20 to 25 mph) could
cause minor winter travel conditions through about sunset.

&&

.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 are having 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 today. 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
County, with most other lower elevation 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 holiday 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 impacts
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 under mostly cloudy/overcast skies.

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
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, but exact details are still uncertain.
Then, after a dry Thursday, another system may approach for the
end of the week and next weekend. Like Tuesday`s 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 coldest temperatures
expected Wednesday behind the next cold front. However, no
arctic outbreaks are expected for the next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1011 AM MST Sun Nov 30 2025

.West of the Continental Divide (KBPI/KJAC/KPNA/KRKS)...

Todays` winter system is a little farther south than forecast,
so have made some adjustments to snow forecast today. Have
removed predominant snow for KBPI/KPNA for this afternoon, with
only a TEMPO group remaining. For KJAC, snow should be complete
other than a brief round of flurries in the next hour, so have
removed PROB30 grouping. Snow still on track for KRKS, but have
decreased intensity slightly, with only brief TEMPO for MVFR
conditions.

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

With the latest weather system staying to the south today, snow
impacts will be minimal. KCPR may see light snow during the
next couple hours before ending. Remaining sites hold mid level
cloud cover through the rest of the afternoon before clearing
overnight. Conditions are favorable for some fog on Boysen
Reservoir tonight, which may briefly drift toward KRIW around
12Z. Chances remain low, so nothing in TAF for now.

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.

&&

$$

UPDATE...Wittmann
DISCUSSION...Hattings
AVIATION...Straub