139
FXUS65 KRIW 280911
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
211 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 cooler 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. A few showers
will move 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 bringing 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 though, 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 of 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 18.
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 /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 900 PM MST Thu Nov 27 2025

VFR conditions to start the period for all TAF sites and for the
majority of this cycle. Increasing upper level clouds lowering
to the mid levels overnight ahead of the next storm system.
Breezy south to southwest winds at all TAF sites gusting up to
around 18kts mainly during the afternoon and strongest mixing.
Timing of cold frontal passage will be the first challenge
between 21-00Z. Winds will increase behind it, first at COD/WRL
with the others to follow into the next TAF cycle gusting up to
25-30kts. Snow will begin shortly after FROPA, mainly the best
chances after 00Z, but a bit later at CPR around 03Z, and RKS
into the next cycle after 06Z. JAC 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.

TAF
KBPI 272

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 PM this afternoon to 8 AM MST
Saturday for WYZ010-011.

&&

$$

DISCUSSION...Hattings
AVIATION...Lowe