374
FXUS65 KRIW 261847
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1147 AM MST Wed Nov 26 2025

.KEY MESSAGES...

- Light snow decreases across northern WY this afternoon, but an
  additional round of light snow (additional accumulations less
  than an inch) is expected Tonight into Thursday morning.

- Largely dry and seasonal weather for Thanksgiving day through
  Friday morning.

- A cold front brings a period of snow from Friday afternoon
  into Friday night across much of the area. Gusty north winds
  and light snow may lead to travel impacts Friday afternoon
  through Saturday.

&&

.UPDATE...
Issued at 1144 AM MST Wed Nov 26 2025

The forecast remains fairly quiet through the Thanksgiving holiday.
Periodic snow showers through the morning will decrease as the
shortwave moves out of the region this afternoon. An additional
trace to 1 inch of snow will be possible through around 2 or 3 PM
this afternoon across the northern WY mountains. Other parts of
the region, including along the I-25 corridor could see snow
showers continue through the first part of the afternoon with a
coating of snow possible. There will then be a 6 to 12 hour
break before another shortwave pushes through with another
coating to an inch of snow possible Thursday morning across
northwest WY. This will be focused only across northwestern
portions of the state with minimal to no impacts. For the rest
of us, seasonal and dry conditions will continue through Friday
morning.

Regarding the upcoming post-Thanksgiving storm, confidence continues
to increase in a widespread light snow event. Timing of the cold
front for Friday afternoon into Friday night remains on track with
the previous forecast and snowfall amounts also remain on track.
Latest NBM Probabilities indicate a less than 25% chance of
exceeding 3" of snow for most low elevation locations east of the
Divide, with lower elevations of Natrona County (including Hwy 20/26
and the Casper area) seeing a 50% chance of exceedance of 3".
Granite Pass and Powder River Pass look to be the locations with
greatest concern for travel impacts, with a 20% chance of >6"
for those locations. Gusty north winds gusting 30 to 40 mph
behind the cold front could also exacerbate travel concerns,
especially across the aforementioned mountain passes. With an
increased number of people on the road given the holiday
weekend, it could be worthwhile leaving a bit of extra time to
get to your destination on Friday afternoon and Saturday.

&&

.DISCUSSION...
Issued at 250 AM MST Wed Nov 26 2025

We are coming up on the busiest travel day of the year, Thanksgiving
weekend. And although no major storms are expected, there may be
just enough of a cornucopia of weather to have a few impacts at
times for some areas.

The first concern is today as a shortwave moves across the area.
Radar is starting to show some showers to the north and west of the
area as I write this, with the steadiest snow this morning as rates
get enhanced by an 125 knot jet streak moving across northern
Wyoming. This looks more like a nuisance than anything as the
best forcing will stay in Idaho and Montana. The most impacted
area will be northwestern Wyoming, with the highest snowfall
amounts across the western Absarokas and eastern Yellowstone as
well as the higher elevations of the Tetons. The Absarokas are
the most sparsely populated area of our area, Yellowstone is
closed for the most part and the highest elevations of the
Tetons are begging for snow right now. With the chance of 6
inches or more less than 1 out of 4, no highlights will be
issued. As for the western Valleys, there will be some snow and
small accumulations but the chance of advisory level snow (four
inches) is less than 1 out of 10. As for East of the Divide,
there could be some snow showers across the northern Big Horn
Basin and down into Johnson or Natrona County, but any
accumulations would be negligible. The only place for a couple
of inches would be the western slopes of the Big Horns, but even
here anything more than 3 inches would be the exception and not
the rule. So, other than some minor impacts to Teton or
Togwotee Passes, not a big deal. Temperatures for the most part
will average close to seasonal normals. All snow should end
around sunset tonight.

There should then be a lull of around 42 hours as we will be in
between systems. Travel for Thanksgiving Day does not look like a
turkey as most of the area will be mainly dry with above normal
temperatures and wind largely on the light side. The exception will
be the northwestern mountains with some orographic snow showers
around but accumulations would be light.

The most impactful weather would likely occur Friday afternoon and
especially Friday night as a cold front drops southward across the
area and brings a chance of snow to most of the area, especially the
northern two thirds of the area. This is looking like the first
accumulating snow across many areas East of the Divide. This does not
look like a major storm though as most areas would see around a six
to 9 hour period of largely anafrontal snow. As for amounts, much of
the area East of the Divide has at least a 1 in 2 chance of an inch
or more. This is notable as both Lander and Riverton, two of the
main snowfall sites, have broken records for the latest measurable
snow by several days. As any higher amounts, with flow largely north
to north-northwest, this favors areas from Thermopolis and East with
upslope flow on the Owl Creek and Bridger Ranges and the southern
Big Horns west back to around Ten Sleep. The highest chance of three
inches, our advisory criteria, looks to be in the higher elevations
of western Natrona County west of Casper to the Fremont County line,
but the chance is at most 1 out of 2.  The Southern Bighorns have
anywhere from a 1 in 3 to 1 in to 2 chance of six inches or more,
but this is south of the passes and impacts would be minimal. There
a couple of factors that could spill the gravy in the forecast
though. One is that in northern Wyoming, precipitation may start as
rain, and falling temperatures could bring slick spots to the roads
as temperatures fall. The second is a jet streak that will be moving
across the area. This could bring some localized snow banding that
could bring locally higher amounts of snow. These are almost
impossible to pinpoint 12 hours out let alone 2 and a half days, so
details are impossible to hash out. We will continue to watch it
though. This is a fast moving system though, with almost all the
snow out of the area by sunrise on Saturday.

Below normal temperatures will then be the big story, as 700
millibar temperatures fall to as low as minus 18 celsius behind
the front. The result will be temperatures remaining below
freezing for many locations through the weekend. And, some
locations could see the first below zero lows on Saturday or
Sunday nights. This will not be a record breaking cold mass, but
it will feel a lot colder than most of November which has been
very mild. On Sunday, another shot of cold air will move south
across the area and interact with a low moving to the south of
the area. This could bring enough lift for some snow mainly
across the southern third of the area. There is very little
moisture to work with though, so amounts would remain light
with the main impacts remaining in Colorado. Flow then turns
more zonal for early next week with temperatures moderating
toward seasonal normals. Another system may approach for the
middle of next week with another chance of snow, but details
this far out are impossible to determine.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1026 AM MST Wed Nov 26 2025

A intense band of snow continues to fall over KJAC this morning
leading to periods of MVFR to IFR conditions. Conditions should
gradually improve shortly after the start of the TAF period. KCPR
may see a brief snow shower or two near the start of the period with
conditions improving by 19Z Wednesday. Other terminals are
seeing mainly VFR conditions to start the period. Winds increase
at KRKS and KCPR near the start of the period with winds of 10
to 20 knots with gusts up to 30 knots possible. Winds decrease
across all terminals this evening shortly after sunset with
mainly light winds through the overnight. Ceilings are expected
to remain VFR for most of the period with the only exception
currently being KJAC. Another weak disturbance is forecast to
move through the area Thursday morning. Once again the highest
likelihood for impacts would be at KJAC. Snow showers look to
move through the area around 09Z to 12Z Thursday with brief
periods of MVFR to possibly IFR conditions at times. KPNA and
KCOD may see a brief light shower but due to the low confidence
only VCSH has been added to these terminals. VFR conditions
should return to all terminals by the late mid to late morning
and prevailing through the end of the period. Mountain
obscuration will be likely throughout much of the TAF period
especially across western and central ranges. Mountain
obscuration may improve near the end of the TAF period of
conditions are expected to begin to improve.

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...
None.

&&

$$

UPDATE...Hensley
DISCUSSION...Hattings
AVIATION...Dziewaltowski