Riverton, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

365
FXUS65 KRIW 150858
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
258 AM MDT Wed Oct 15 2025

.KEY MESSAGES...

- Showers increasing across the area as a weather system moves
  in from the southwest. A few thunderstorms are possible as
  well.

- Turning colder tonight and Thursday with moderate snow
  expected in the western and northern mountains and rain in the
  lower elevations.

- Another cold front may bring additional showers on Saturday.

&&

.DISCUSSION...
Issued at 253 AM MDT Wed Oct 15 2025

The question of the day continues to be what will happen with the
upper level low that is now swirling over California and will move
toward and over the Cowboy State over the next 36 to 48 hours. And
the good news is that there is more agreement in the model guidance
this morning, although there are some differences in the exact track
that will make a difference in potential precipitation amounts (try
saying those three words fast five times, a bit of a tongue
twister). Well, let us dive in.

We currently have a few areas of mainly light showers moving
northward across the area. A couple of thunderstorms are also noted,
but nothing strong and these are mainly in Idaho. Today looks like
it will be inverse of yesterday, when we had more shower coverage in
the morning and then decreasing in the afternoon. Showers should
become more numerous in the afternoon as the low gets closer to the
area. And this is where we still have some uncertainty with the
track of the low. Some guidance, like European model, show the low
moving further south, which would bring a better chance of showers
across central Wyoming this afternoon and tonight. Others, like the
GFS, bring the low around 75 miles further north, and this could
bring a dry slot into central Wyoming, keeping things largely dry.
For now, we kept some POPS in the area but chances are generally less
than 1 out of 3 in any given area before better chances move in
later Wednesday night as the low makes a closer approach. The most
numerous showers will be across western Wyoming though. And, there
could even be a few stronger thunderstorms. CAPE is rather limited,
only around 300 J/Kg at the most. However, lifted indices drop to
around minus 3 in the afternoon across portions of Johnson and
Natrona County. There will be decent upper level divergence as some
direction shear as well. Nothing widespread is expected but there
could be a few more feisty storms. The Storm Prediction Center
agrees and has issued a marginal risk for Natrona County.

The other concern is snow. Few problems are expected through the
daylight hours today, as snow levels should remain above 8500 feet
and even above this still warm ground and borderline temperatures
should melt snow on roads. A cold front will press across the area
tonight and drop snow levels to around 7000 to 7500 feet by Thursday
morning and possibly as low as 6500 feet in some areas East of the
Divide as 700 millibar temperatures may fall as low as minus 4 to
minus 5. As for the advisories, they still look reasonably so few
changes will be made this morning. The areas with at least a 1 out
of 2 chance of 6 inches of snow or more are covered by the
advisories for the most part. I do have a small concern that some
portions of the Bighorn range may receive 6 inches or more but these
would be the higher peaks and therefore impacts would be limited.
The steadiest precipitation still looks to fall in the 18 hour
period from late tonight through Thursday afternoon, with showers
later Thursday as the low moves away to the south and east. As for
total precipitation, most areas north of a Kemmerer to Casper line
have at least a 1 out of 2 chance of a quarter of an inch or greater
over the next 24 hours. The highest amounts still look to be in
northwestern Wyoming, with a least a 1 out of 2 chance of greater
than three quarters of an inch of QPF over the same time period.

Most guidance is showing Friday as a dry dry with ridging over the
area. Another fast moving cold front will move in from the north on
Saturday. There continues to be differences in guidance in regards
to shower chances though. For now, we leaned toward the drier end
since the front is of continental origin and doesn`t have a lot of
moisture to work with. Drier and warmer weather then returns on
Sunday.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1133 PM MDT Tue Oct 14 2025

A closed low along the CA/NV border has ejected a shortwave
northward across northern Utah late Tuesday evening. This has
resulted in scattered showers and even a few thunderstorms since
03Z/Wednesday over western Wyoming. This wave continues north
through the overnight hours. Meanwhile, IFR ceilings have
settled in at KCOD, with IFR/MVFR anticipated to develop at KCPR
and KWRL between 09Z-12Z/Wednesday. These clouds will be slow
to erode likely taking until 17Z-19Z/Wednesday to at least lift
and eventually dissipate by mid-afternoon. Strong southerly flow
aloft coupled with more sunshine will allow for scattered
convection to develop across the forecast area during the
afternoon. PROB30 rules at all terminals between 20Z-01Z
Wednesday afternoon with little confidence in exact timing or
impacts at any specific site. South wind 15-30kts increases at
KRKS around 17Z/Wednesday and during the early afternoon at
KBPI, KLND, and KPNA before diminishing around sunset. Lower
clouds and a better chance of rain arrive after 03Z/Thursday as
the closed low approaches the state. Mountains frequently
obscured until around midday Wednesday across the Bighorn Basin
and the vicinity of KCPR.

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 6 PM this evening to 11 PM MDT
Thursday for WYZ002-012-014-015-024.

&&

$$

DISCUSSION...Hattings
AVIATION...CNJ