205
FXUS65 KRIW 281144
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
444 AM MST Fri Nov 28 2025

.KEY MESSAGES...

- A cold front will bring a period of snow to most of the area
  late today and tonight, likely bring travel impacts.

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

- A colder and wetter pattern is likely for much of next week.

&&

.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 /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 435 AM MST Fri Nov 28 2025

VFR conditions to start the period for all TAF sites through 18Z.
Increasing clouds lowering to MVFR after 18Z ahead of the next
storm system. Breezy south to southwest winds at all TAF sites
gusting up to around 18 kt mainly during the afternoon and
strongest mixing. Timing of the cold frontal passage will be
the first challenge between 18Z and 21Z. Winds will increase
behind it, first at KCOD/KWRL with the others by 00Z gusting up
to 25-30 kt. Snow will begin shortly after FROPA, mainly the
best chances after 00Z, and KRKS between 04Z and 07Z. KJAC is
spotty to begin earlier, and thus, carrying VCSH after 20Z.

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 5 PM this afternoon to 8 AM MST
Saturday for WYZ010-011.

&&

$$

DISCUSSION...Hattings
AVIATION...LaVoie/Lowe