Riverton, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

162
FXUS65 KRIW 251243
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
543 AM MST Thu Dec 25 2025

.KEY MESSAGES...

- Snow continuing in the western mountains and strong wind from
  South Pass through Casper today, both decreasing in the
  afternoon.

- Another day of record breaking high temperatures is likely
  this afternoon.

- Another weather system will bring the next chance of snow and
  wind from Friday into Friday night.

- A Canadian cold front moves through the area Saturday and
  Saturday night and brings more seasonable temperatures for
  Sunday into Monday.

&&

.DISCUSSION...
Issued at 152 AM MST Thu Dec 25 2025

The weather has been exceptionally abnormal across western and
especially central Wyoming for much of this month. And this being
Christmas Day, it remains me of my childhood in the late 70s and 80s
when the Christmas specials played on network TV, usually CBS.
I can still hear the old 5 second bumper of "A CBS Special
Presentation" with the horns and drums. It always meant
something cool was coming on. And the special I am referring to
is the 1974 Rankin-Bass stop motion animation "A Year Without A
Santa Claus." It featured the two characters of the Heat Miser
and the Snow Miser, representing the warm and cold weather.

This year, it seems like the snow miser has been on a two month long
leave of absence with only cameo appearances and is still
nowhere to be found. At the office as I write this, our office
is sitting at 53 degrees, which is the average HIGH temperature
for Raleigh, North Carolina, where I went to college back in the
dark ages called the 90s. And it looks like we will have
another day of record warm temperatures, mainly east of the
Divide. One of things bringing this though is strong to high
wind, courtesy of an approaching trough and an 120 knot jet over
the area. We have High Wind Warnings out roughly from South
Pass through Casper through 11 am this morning. Most guidance
shows 700 millibar wind remaining 50 knots or more through this
period before decreasing, and bringing lighter wind as a result.
The area still looks good with most areas having at least a 3
out of 5 chance of wind gusts past 55 mph. There could be a few
high gusts around Lander as well, but these would be isolated.
We will issue a Special Weather Statement to cover for this.

And we have a snowy part of the system as well. Snow has been
falling largely above 8000 feet today, bringing slick conditions to
the mountain passes, mainly Teton and Togwotee passes. The current
Advisory looks to be in good shape right now, although a bulk
of the snow should fall before noon as the best forcing moves
east of the area by that time. We will continue as is for now.
Snow levels may fall to around 7000 feet this afternoon, so
there could be some light accumulation in the valleys, but
nothing to write home about.

There should be a lull in the snow and wind later this afternoon and
through tonight. Then, another Pacific trough will approach the
area. There is a bit more uncertainty with this one, as the
models have different placement of the heaviest QPF. Ensemble
guidance gives a greater than 4 out of 5 chance of over 6 inches
of snow in the western mountains through Saturday. Chances of
12 inches are more limited though, generally less than 1 out of
2. And areas that have the greatest chance are the Wind River
Range and southwestern Yellowstone, areas where impacts are
fairly limited. I could see some more highlights here, but will
hold off for now with the current Advisories so as not to
confuse people. One difference here is that colder air will be
in place, with 700 millibar temperatures falling to minus 9
Celsius by Friday evening across the western valleys, making
most of the precipitation in the form of snow. Chances of over
3 inches in the valleys remain small, generally 1 out of 3 or
less though. Although there will not be a white Christmas, it
could be a white Boxing Day, at least late in the day. Some snow
could even make it in southern Wyoming in the afternoon or
evening, but accumulations here should remain on the light side.

As for east of the Divide, there will be one more mild day.
However, the peak of the heat will be today with temperatures
about 10 degrees cooler on Friday than Christmas day as 700
millibar temperatures fall about 5 degrees Celsius. It will
still be well above normal though. There could be another period
of high wind as well, as the pressure gradient tightens ahead
of the trough and southwest flow increases with 700 millibar
wind again reaching 50 to 55 knots. Ensembles are giving a
greater than 1 out of 2 chance of wind gusts past 55 mph from
South Pass through Casper and also in the Lee of the Absarokas.
We will hold off on any highlights for this, given the current
ones in effect. If conditions look likely, we can issue on the
day shift today or early Friday morning. As for precipitation,
chances look small again with the downsloping flow.

There will be one more system for Saturday, and that will really put
an end to the mild weather, at least temporarily. This will be
in the form of a Canadian cold front that will bring a colder
air mass from, you guessed it, Canada. As for precipitation,
given the continental origin, moisture is limited and with the
front`s fast movement, amounts would be light. Many areas east
of the Divide could see some snowflakes for the first time in a
while though on Saturday into Saturday night.

Temperatures then return to levels more normal for late December on
Sunday. The numbers we have in the forecast may be coldest they
could get though. If there is little or no snow on the ground,
albedo would be limited. It will feel rather cold though, given
the recent balmy weather. The cold weather won`t last long
though, as ridging builds back over the area and flow turns
westerly again for much of next week. This will bring a return
to above normal temperatures, although not as warm as this past
week. It will also likely be rather windy at times given the
fast zonal flow.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 345 AM MST Thu Dec 25 2025

West of the Continental Divide...KJAC/KRKS/KPNA/KBPI Terminals

Light rain, but VFR conditions, continue at KJAC/KBPI/KPNA with
low VFR conditions. Periods of a more steady rain and marginal
MVFR conditions will be possible between 13-17Z at KBPI/KPNA and
between 16Z and 19Z at KRKS. Periods of these conditions will
be possible between 20Z and 00Z at KJAC, as rain primarily ends
by 16Z. Dry and VFR conditions will then be in these locations
until 06Z, when snow redevelops over the west with marginal VFR
conditions. Otherwise, wind gusts of 25kt will occur at KRKS
through 01Z. Areas of LLWS will decrease across the area and end
by 18Z. However, areas of LLWS will redevelop across much of the
area by 12Z Friday.

East of the Continental Divide...KCPR/KCOD/KRIW/KLND/KWRL Terminals

VFR conditions and dry weather expected. Stronger downsloping
winds will continue at KCPR and KLND through 17Z, decreasing to
30-35kt through the afternoon. Wind gusts around 25kt will
continue at KCOD through the period. Winds will increase at KRIW
and KWRL by 20Z with daytime heating and mixing. These winds
will decrease around 00Z-01Z. Areas of LLWS will remain in place
across much of the area through 18Z,with isolated areas
redeveloping by 12Z Friday.

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

&&

.CLIMATE...
Issued at 152 AM MST Thu Dec 25 2025

Another day of record high temperatures are likely today across
much of the area. There were eight record high temperatures at
our nine official climate sites yesterday, with only Big Piney
not having a record high. Two locations, the Riverton Airport
and Greybull had their all-time warmest December temperature on
the afternoon of the 24th. This brings the total of record high
temperatures this month so far at our nine official climate
sites to 59.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST this afternoon for
WYZ012-014.

High Wind Warning until 11 AM MST this morning for WYZ015-019-
020-022.

&&

$$

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