817
FXUS65 KRIW 282234
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
334 PM MST Fri Nov 28 2025

.KEY MESSAGES...

- A cold front brings snow to much of the area late tonight
  through early Saturday morning. Wind and falling snow may
  impact travel, especially over Johnson and Natrona Counties.

- The coldest air of the season moves in tonight through the weekend,
  with some locations seeing below zero low temperatures
  Saturday night.

- A cold and wet pattern looks likely for much of next week.

&&

.UPDATE...
Issued at 1128 AM MST Fri Nov 28 2025

The overall message with this update remains the same, with
only minor changes to snow amounts and winds with the latest hi-
res models. The main change to the forecast is the addition of a
Winter Weather Advisory for the lower elevations of Natrona
County, including Casper and portions of I-25. Given amounts
near 3 inches, gusty winds with the front, and it being a
holiday weekend, an advisory covers the overall travel impacts
expected. Greatest impacts for this area occurs between about
6pm and 3am MST when the heaviest snow and greatest winds
occur. Snow banding may bring brief and localized greater
impacts and snow amounts. Snow amounts should also increase
further south in Casper town as upsloping aids in snow
production. Some impacts may linger into early Saturday morning,
but snow and wind should be on a decreasing trend.

&&

.DISCUSSION...
Issued at 206 AM MST Fri Nov 28 2025

As I`ve said before, I`m getting old. And the weather pattern now
reminded me of something that many people do on Thanksgiving, watch
football, assuming they haven`t passed out from the tryptophan
in the turkey. The first color commentator I remember was on
Monday Night Football, the late, great Don Meredith. And one of
his famous lines when a victory was certain, was "Turn Out The
Lights, The Party`s Over". And that is what will happen to the
unbelievably nice weather we have had through November (if you
like mild weather). Many locations are averaging 10 or more
degrees above normal, with some having the warmest November so
far in station history. However, this will come to a crashing
halt tonight and through the rest of the week.

It has also been snow free for a lot of locations. That will change
late today and especially tonight, as the first accumulating snow
arrives to most areas east of the Divide. We will have one more
mild day today though, with some locations approaching 50
degrees. A few showers will move through this afternoon, but
the main impacts will be after sunset tonight.

A cold front will drop into northern Wyoming late this afternoon and
then move southward through the night, ushering much colder air. It
will also bring in the aforementioned snow of the anafrontal
variety. The system is a quick mover and does not have a lot of
moisture to work with, and this should keep snow amounts down
somewhat. Probabilistic guidance is giving around a 1 in 2
chance of 6 inches or more snow only across the higher
elevations of the Tetons and southern Bighorns where impacts
will be few. As for the lower elevations, advisory amounts are
generally 3 inches or more. And chances are generally 1 out of 4
for the most part. There are a couple of exceptions. With the
north-northwest flow behind the front, the favored
orographically enhanced areas around Ten Sleep and east of
Thermopolis have around a 2 in 5 chance of 3 inches or more, as
well as some portions of Casper to the south of Wyoming
Boulevard. We have held off on advisories here though, since
this is a small part of those zones. There are a couple of other
factors though. There will be an 110 knot jet streak moving
over the area later tonight to help enhance lift. This could
also increase the chance of snowbands, which could locally
increase snowfall amounts. It will also bring gusty, and in some
locations, strong winds. This will especially be the case in
the favored cold advection / northwest flow areas like Johnson
County and the northern Bighorn Basin. Some gusts to 50 mph
could occur with the snow and cause travel problems. Snowfall
amounts look fairly limited in the northern Bighorn Basin, but a
little heavier in Johnson County. With this, along with the
area having two Interstates, we have decided to issue a Winter
Weather Advisory for Johnson County, mainly for blowing snow and
travel impacts than for snowfall amounts. As for timing, the
greatest impact would be from around 8 pm tonight through around
4 am Saturday morning. Following that, snow should come to an
end as the front moves away to the south and east.

The main concern then shifts to cold temperatures, the coldest
of the season so far. Northern locations will likely stay in the
teens for highs on Saturday. Most locations east of the Divide
will have at least a 4 in 5 chance of low temperatures in the
single digits Saturday night as 700 millibar temperatures fall
as low as minus 18C. Johnson and Natrona County have around a 2
in 5 chance of the below zero low temperatures. Chances
decrease further west though, as cloud cover may keep
temperatures a bit warmer.

And the reason the clouds will increase is another fast moving wave
diving in from the northwest. This is another fast mover and has
even less moisture to work with than tonight`s front. It will bring
some light snow to roughly the southwestern half of the area on
Sunday. However, the best forcing should remain to the south and
west. The chance of advisory level snow is basically zero at this
point.

Following that, we will be in a progressive, northwest flow
pattern. Monday at this point looks to be a dry day with
moderating temperatures. Another system will approach the area
with the next chance of snow for midweek, although this does
not look like a large storm at this point. Details are still
hard to nail down this far out.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 330 PM MST Fri Nov 28 2025

Front just starting to cross the WY/MT border at 21Z, with winds
quickly picking up from the north. Snow also spreading southward
with the advance of the front. Timing still on track, with
KCOD/KWRL/KJAC snowing now through 06Z, and central WY 03-09Z. Once
the snow ends for the northern sites, they will clear out through
the night, with mostly clear skies by 12Z. Central sites will hold
onto low clouds through the night, with KCPR possibly seeing cigs
right at the sfc with some fog possible.

KBPI/KPNA will see a brief period with a lower chance for snow this
evening, before skies clear out overnight again. KRKS will also see
brief snow chance this evening, but lower clouds more likely to hold
there through the rest of the night.

Conditions Saturday will be VFR, with a return of some high cirrus
late morning into the afternoon.

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 until 8 AM MST Saturday for WYZ010-011-
020.

&&

$$

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