346
FXUS65 KRIW 242357
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
557 PM MDT Sat Oct 24 2026

.KEY MESSAGES...

- Remaining cool behind last night`s cold front. Low clouds
  persist across the Wind River Basin and northwestern portions
  of the area.

- A weak weather system brings a few showers late tonight into
  Sunday, but rain and snowfall amounts will remain on the light
  side.

- A more potent system arrives Monday night and Tuesday,
  bringing rain and snow showers to northern and western Wyoming
  and gusty winds to central and southern Wyoming.

- It will remain cool with temperatures trending warmer late in
  the upcoming week.

&&

.UPDATE...
Issued at 1235 PM MDT Sat Oct 24 2026

No major changes with this update, with dry and cool weather today.
Clouds slowly erode through the afternoon, evident by current
satellite imagery. A weather system late tonight and through
Sunday brings precipitation chances (15-30%) to the area, mostly
for the southwest portion of the state. Any totals are light,
with maybe around 0.1" for a heavier shower.

&&

.DISCUSSION...
Issued at 228 AM MDT Sat Oct 24 2026

We are currently experiencing some rattling at the Riverton Weather
Abode. This is coming compliments of our good friend cold advection,
following the passage of a cold front. Some of the more wind prone
areas, like near Buffalo, have seen wind gusts around 50 mph
tonight. These events are usually short-lived though, and most
of the wind should be over by sunrise.

We are currently in a fast moving pattern, which will bring a few
chances of precipitation to the area. The area will be in between
systems today, which should bring a dry but cool start to the fourth
weekend of the month, with temperatures averaging around 5 degrees
below normal. The next chance of showers arrives tonight as the
upper level low now located over Arizona, that has been
bringing all the severe weather to the Desert Southwest, moves
to the northeast. Thankfully, it will be significantly weaker
when it arrives here tonight and Sunday. Recent model trends
keep the low further east, taking it over southeastern Wyoming,
and also keeping a bulk of the moisture east of the area. As a
result, precipitation amounts should remain on the light side,
with all locations except the Wind River Range having a less
than 1 in 2 chance of a tenth of an inch or more of
precipitation. Otherwise, expect a mostly cloudy and seasonable
day.

We should then have a period of quiet weather on Monday as there
will be another gap in areas of low pressure. Then the second system
arrives Monday night into Tuesday. This system is of Pacific origin
and will have a bit of moisture and jet energy to work with so
impacts will be greater. However, with the flow being zonal and
rather fast, the low should be a fast mover to limit the
duration of those impacts. As for the precipitation, most
guidance shows the highest amounts across northern Wyoming,
especially in the western mountains with a period of orographic
enhancement. Most areas in the northwest have at least a 3 out
of 4 chance of a tenth of an inch or more of QPF, with a 1 in 2
chance of a quarter of an inch or more. Due to the fast movement
of the system, chances of a half an inch or more are generally
less than 2 out of 5. The next question is how much of this
precipitation will be snow. Some guidance shows 700 millibar
temperatures falling as low as minus 6C, which would lower snow
levels to valley floors. The question is how much moisture will
be left over when the cold air arrives. In the probabilistic
realm of the ensembles, most of the mountains, as well as the
Jackson Valley, have at least a 1 in 2 chance of an inch or snow
or more, with a similar chance of over 3 inches above 8500
feet. However, due to the fast movement of the system, the
chance of 6 inches is less than 1 out of 5, so advisories look
unlikely at this time. Travel could be difficult for a time,
since there will be an 100 knot jet over the area at the time,
and there could be some blowing snow over the passes that could
reduce visibility.

And the strength of the jet, along with some strong southwest flow
on the south side of the low, will bring strong wind to central and
southern portions of the area on Tuesday. The NBM ensemble shows at
least a 1 in 2 chance of wind gusts past 40 mph on Tuesday
afternoon, with the area from Muddy Cap through Casper having at
least 1 in 2 chance of gusts over 50 mph. The chance of gusts over
60 mph is under 1 in 4 for the major travel corridors, so wind
highlights look unlikely at this point, but we will have to
watch it closely.

Quieter conditions should then move in for most of the remainder of
the work week with ridging building over the area, bringing
mainly dry conditions and above normal temperatures. A few
orographic showers may occur across western Wyoming, but it
should be dry most of the time. A stronger system may approach
for next weekend, but guidance diverges substantially this far
out so details are very difficult to nail down.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 345 PM MDT Sat Oct 24 2026

Clouds have lingered in the Wind River and Upper Green River
Basin longer than expected, but are expected to stay VFR by the
start of the TAF period. SCT-OVC FL120-200 clouds will
generally be confined south of a KAFO-to-KGEY line through the
forecast period. Ceilings of FL050-100 will occur over southern
portions by 12Z, spreading into the Upper Green and Wind River
Basins by 18Z. This will also result in mountain obscurations
over the Wind River Mountains and Salt River/Wyoming Ranges.

Winds will remain light (11kt or less) for all terminals
through the period, with most locations maintaining some
easterly component. An area of light showers will develop
between KRKS and KRIW around 12Z, gradually shifting toward the
north- northwest through the rest of the morning. Little to no
impact is expected with these showers and have left any mention
out of the forecast for KRKS, KRIW and KLND at this time. There
is less than a 10% chance for showers for areas east of a KEMM-
to-KCOD line Sunday afternoon.

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...Wittmann
DISCUSSION...Hattings
AVIATION...LaVoie