040
FXUS65 KRIW 270808
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
208 AM MDT Tue Oct 27 2026

.KEY MESSAGES...

- Most showers should end by sunrise. Otherwise, it will be
  windy day for most today with wind gusts over 50 mph likely (a
  4 out of 5 chance) near the Wind River Range and from Muddy
  Gap through Casper.

- A second weather system brings rain and snow showers Tuesday
  night, especially in southwestern Wyoming where some light
  snow accumulation is possible (a 1 in 2 chance in the lower
  elevations).

- The next chance of showers arrives this weekend, with the
  potential of a more substantial system Sunday night into early
  next week.

&&

.DISCUSSION...
Issued at 204 AM MDT Tue Oct 27 2026

So far, the forecast is working out fairly well. An area of rain and
snow associated with the front and trough is working its way across
western Wyoming. It is moving quite quickly and other than a few
orographic showers in the northwestern mountains, should be out of
the area by sunrise, with a majority of the area dry for most of the
day. Any snowfall amounts should remain sub advisory, but some of
the mountain passes could be slick into the morning before the snow
melts off after sunrise.  Our attention then turns to strong to
potentially high wind. This will be mainly in the wind prone areas
like around South Pass and from Muddy Gap northeastward through
Casper.

There are some factors for it. We will have an 100 knot jet streak
over the area today. Some models also show wind at 700 millibar
millibars around 50 knots, especially through around 2 pm when there
will be some decrease. There are some factors against it though.
Most MOS guidance shows sustained winds at the Casper airport only
around 22 to 26 knots, I would like to see 30 knots to have more
confidence for high wind. Next, we dive into the wonderful world of
ensemble and probabilistic guidance. The National Blend of Models
ensemble gives a greater than 1 in 2 chance of wind gusts over 30
mph across most of the area. However, for high wind we are
interested in wind gusts over 55 mph. The main area with the
strongest wind is over the higher elevations of Casper Mountain and
the Green and Rattlesnake Ranges, where criteria is 75 mph gusts.
There is an area on south side of Casper that has a greater than 1
in 2 chance of gusts over 55 mph. However, criteria is higher here,
gusts have to be over 65 mph. And chances of this are less than 1
out of 4. There could be an isolated high wind gust in places like
Wyoming Boulevard on the South Side of Casper and along Hat Six
Road, but this would be the exception and not the rule. So, we chose
not to issue a high wind warning at this time. Wind should decrease
later this afternoon as the system moves away and the pressure
gradient begins to relax.

A second shortwave will approach the area on Tuesday night and bring
another round of showers. This one is similar to this one in that 1)
It will have some upper level dynamics to work with in the form of
the right rear quadrant of a jet streak and 2) It will be a fast
moving system, with most of the precipitation falling in a 6 to 9
hour period, most likely from 9 pm until around sunrise Wednesday. I
am still concerned the current forecast may be a bit underdone on
QPF amounts, especially in southwestern Wyoming. I could see an
inch or two of snow in places like Kemmerer, Farson and even Big
Piney and Pinedale with a bit more in the Salt and Wyoming Range and
the western Wind River Range if banding sets up right. The only
location with a greater than 1 in 2 chance of 4 inches or more is
the highest elevations of the Wind River Range though, so now
highlights will be issued. A few showers are possible East of the
Divide, but the chance is generally less than 1 out of 3 and any
amounts should be rather light.

Wednesday and Thursday look more tranquil as ridging builds
over the area and brings dry conditions and above normal
temperatures. The next concern shifts to a potential weekend
system that could bring the next round of rain and / or snow.
There has been somewhat in slowing of the progress of the
system, so Friday may end up being mild and dry as well,
especially East of the Divide. Most of the weekend details are
still uncertain. The best chance of showers would be across
western mountains through most of Sunday, but there is a large
spread in guidance as to how numerous showers would be. However,
Sunday night into Monday are starting to look interesting. A
closed flow may pass near or just south of Wyoming and with
north flow into the area, it may be cold enough for the first
accumulating snow in many of the lower elevations East of the
Divide. Now, it is still a weak out and a lot can change, but it
is something to watch as we head later in the week and into the
weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1030 PM MDT Mon Oct 26 2026

MVFR ceilings at JAC to start the period due to a light
rain/snow mix that will push to BPI/PNA within an hour, each for
about 3-4 hours as this wave pushes through overnight into
Tuesday morning. Light rain could make it over to COD between
09-12Z but not as high in confidence but no impacts expected
even if it does. Gusty winds with this precipitation but soon
to diminish after it pushes through. Winds increase once again
Tuesday morning after 14-16Z, strongest at CPR up to 30kts and
COD 25kts. This will decrease towards sunset after 00Z with
radiational cooling with lingering mid level clouds in the
afternoon and remainder of the period. Dry conditions after this
wave with no other weather elements at this time.

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.

&&

$$

DISCUSSION...Hattings
AVIATION...Lowe