480
FXUS65 KRIW 120838
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
238 AM MDT Mon Oct 12 2026

.KEY MESSAGES...

- Showers continue today, with the greatest coverage across
  western Wyoming.

- The most numerous showers shift to southern and central
  Wyoming Tuesday afternoon through Wednesday.

- Snow will continue in the higher elevations of the mountains,
  with snow levels falling to the lowest elevations (between
  7000 and 7500 feet) from later Tuesday through Wednesday
  morning.

&&

.DISCUSSION...
Issued at 232 AM MDT Mon Oct 12 2026

Fall has finally arrived to the area. Sunday was the coolest day may
locations have seen since May. And it looks like we are through with
the record high temperatures for a while, although we should see
some moderation in temperatures toward seasonal normals toward the
end of the week.

The moisture from Rachel that moved over the area today is now
moving away to the north and east. We still have some showers across
the area, although most of the precipitation is on the light side.
Notice how I said precipitation though. There has been some snow in
the mountains. And even in the lower elevations, we have seen some
mixing in places like Cody and Powell, although there have been no
reported problems with roads. The general trend should be down
through the night, although some rain and mountain snow will linger
until morning.

Our attention now turns away from the moisture from Rachel to that
big bowling ball to west, AKA an upper level now swirling over
Oregon. This feature has been giving me fits over the details of
its direction, and, most importantly, the ultimate impacts of the
weather across western and central Wyoming. And the good news is we
finally have somewhat better agreement in the path of it. The models
are digging the low a bit further south, both the operational GFS
and European models, as well as a majority of the ensemble members
dig the low further south, moving across the Great Basin to near Las
Vegas by Tuesday evening. The result at this point looks to be
somewhat less precipitation. There should be somewhat of a lull this
morning as we will be in between systems. There are some indications
of a weak meso low that may try to move into the area, but the
models are split on this. Nevertheless, the majority of the showers
will fall West of the Divide today, especially during the day.
Northeastern portions of the County Warning Area may have a mainly
dry day today. Another wave should bring an increase in showers
tonight. However, there is a decent spread of where the most
numerous showers will fall. And it will be a cool day as well, with
below normal temperatures. As for precipitation amounts, I will talk
about those in separate paragraphs further down. As for the high
wind warning, we will let it ride until expiration. We will let
the freeze warning ride for now. And, with the cold comes snow.
We will also discuss that in another paragraph.

Tuesday looks like a similar day with cool temperatures and most of
the showers across southern and western Wyoming with fewer further
to the north. The low will begin to make a turn toward the northeast
Tuesday night and into Wednesday. This is when the wettest period
should be for areas East of the Divide as flow turns more easterly,
bring an upslope component. It should be noted though that with the
low further to the south, we will closer to the edge of the moisture
so precipitation amounts have been cut, to about half of what they
were yesterday at this time. Showers should linger into Wednesday
before gradually ending as we head into Thursday as the low moves
away. Which way it moves depends on what model you believe, but most
agree it will move away. Dry weather should then return Friday and
into the weekend as flow turns zonal as flat ridging builds, bring a
return to near normal temperatures.

PRECIPITATION AMOUNTS...I will break this up into two different
segments. The first will be the twenty four hours through tonight.
No surprise, the highest amounts will be across western and southern
Wyoming, with the 1 out of 2 chance line roughly running south of a
Jackson to Casper line. The chance of a half an inch or more is
generally 1 out 2 across the southwestern quarter of the state. The
epicenter is, no surprise across the western slopes of the Wind
River Range were where is a 1 out of 2 chance of an inch or more.
Amounts decrease further north where many areas may end up with a
mainly dry day. As for Tuesday through Wednesday night, all areas
have at least a 1 in 2 chance of a quarter of an inch or
precipitation, south of a Jackson to Buffalo line as the main
concern for precipitation shifts to central and southern Wyoming.
When we bump it up to an inch, the main concern switches to the east
to northeasterly upslope locations East of the Divide, mainly
along and south of US 20 26 from Dubois to Casper, with lesser
amounts across western Wyoming as the upper level low moves
further to the east. Some locations, especially the Wind River
Range have the potential to pick up an additional two inches of
QPF by Thursday morning.

SNOWFALL...Snow level at this time are generally running between
8000 and 8500 feet this morning in central Wyoming to around 7000
feet in northern Wyoming in regards to accumulating snow. Through
the day today, snow levels should remain in in this vicinity so
above most passes. The exception would be Togwotee although warm
ground temperatures are keeping any impacts from the roads. The best
time for snow levels to lower would be later Tuesday through
Wednesday as flow turns more northeast. The 700 millibar
temperatures way fall as low as minus 2 to minus 3, which could
bring snow levels down as low as 6500 to 7000 feet, especially in
vicinity of the Wind River Range, Tetons, Absarokas and Salt and
Wyoming Range. This period from Tuesday through Wednesday looks to
be the most impactful of the period, so this is when the first
winter weather advisories my be needed. For three inches of snow,
most of the mountains ranges have at least a 1 in 2 chance at the
higher peaks. Advisories in the mountains are for 6 inches or
greater though. And although a few locations have this, the most
widespread location would be the Wind River Range, where most
locations above 9000 feet have at least a 3 out of 4 chance. A
decent portion of the Wind River Range has a 1 out of 2 chance of at
least 12 inches of snow, but this would be in places well away from
the main travel routes. So, the likely highlights needed would be
advisories and not warnings. Some of the highest locations, like
Gannett Peak, may end up with over 30 inches of snow by the time the
upper level low moves away on by Thursday.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 950 PM MDT Sun Oct 11 2026

A weather system continues to bring rain and low clouds to the area.
There will be frequent reductions in flight category due to low
clouds and reduced VIS from rain. Some snow will mix in with rain at
KCOD at times. Conditions will generally be MVFR to IFR, but brief
reductions to LIFR cannot be ruled out at KCOD and KWRL. There will
be improvement to VFR at times as well for most terminals, which is
reflected in the TAFs. CIGS at KCOD likely (70%) will not get above
MVFR during the TAF period.

Wind will be breezy at KRKS and KCPR tonight, but will decrease
around 08Z at KRKS. A cold front along the Continental Divide should
retreat northward early in the TAF period, which will bring
southerly wind to KCPR, which will be short-lived as it pushes south
to the Divide again by mid-morning. Frequent mountain obscuration
continues through the TAF period.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 9 AM MDT this morning for WYZ003>006.

High Wind Warning until 6 AM MDT early this morning for WYZ019-
020-028>030.

&&

$$

DISCUSSION...Hattings
AVIATION...Rowe