257
FXUS65 KRIW 240001
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
601 PM MDT Fri Oct 23 2026

.KEY MESSAGES...

- Valley rain and mountain snow is forecast across western and
  northwestern Wyoming through 10 pm, at least, before shifting
  into northern and central Wyoming after sunset.

- Southwest winds with gusts of 45 to 55 mph are expected this
  evening in the Lander Foothills. Wind gusts of 20 to 35 mph
  are expected elsewhere.

- A cold front will bring a northerly wind shift tonight, with
  wind gusts between 40 to 55 mph in the Bighorn Basin and
  Johnson County.

- Much cooler temperatures are forecast this weekend behind this
  weather system. They will be near seasonable to below average
  for this time of year.

&&

.UPDATE...
Issued at 118 PM MDT Fri Oct 23 2026

Current (1PM MDT) observations are showing wind gusts ranging from
20 to 35 mph across the western 1/3rd of Wyoming to 45 to 60 across
Natrona and Johnson Counties, the Lander Foothills, and other wind
prone areas. These gusty winds are forecast to continue through the
day as the pressure gradient tightens ahead of the approaching cold
front. Given these wind gusts across Natrona County and the Lander
Foothills, a High Wind Warning has been issued through 6PM this
evening. Although winds are just as high across Johnson County, no
High Wind Warning is in effect due to the Red Flag Warning covering
both the wind and erratic fire behavior threat.

Otherwise, the forecast remains track with increasing low elevation
rain and mountain snow shower activity across west and northwest
Wyoming as the front makes its way into the state. As the front
shifts to the south and east, a few showers are still expected
across the Bighorn Basin and the Bighorn Mountains after
sunset. The current timing for the greatest coverage of
precipitation is from 2PM through midnight. There is also a 20
to 40% chance of light showers on the east side of the Wind
River Mountains early Saturday due to favorable upsloping. In
addition to the precipitation chances, post- frontal gusty north
winds are forecast across the Bighorn Basin, Wind River Basin,
and Johnson County overnight into early Saturday morning. This
windy Friday will give way to a cool, fall-like Saturday.

&&

.DISCUSSION...
Issued at 130 AM MDT Fri Oct 23 2026

IR shows cooling cloud tops across the CWA as the tropical
moisture has begun to interact with the open wave pushing up
from the southwest nearing the CWA. WV imagery shows a
disjointed PFJ dipping around the trough to the west but mainly
to the north into southern Canada with a 120-130kt jet max
helping to aid the aforementioned system that will affect the
CWA throughout Friday and lingering into Saturday. Radar shows a
few scattered light showers pushing across Natrona County that
will diminish before sunrise Friday morning. The main push of
precipitation will come from eastern Idaho and northern Utah
later through the overnight hours that will eventually spread
east to the Divide later in the morning. Some rumbles of thunder
are possible with instability values in the 100-200 J/kg range
into the afternoon. PVA anomalies look to be more constrained
over Idaho and into southern Montana, limiting any significant
accumulations but limited mountain snow is likely for the higher
elevations of the western mountains. More prominent for the
Tetons and into Yellowstone, 3 to 5 inches are possible but with
lower confidence at this time (30-40%). Freezing levels will
remain above 10kft ahead of the cold front later in the
afternoon with limited precipitation at that time of FROPA.

Winds will be of concern today remaining elevated in many areas
into Friday morning already, with a possible weak mountain wave
off the southern Winds into the eastern parts of the Wind River
Basin. Gusts up to 30 to 35 mph are possible with this but not
of high concern at this time. Winds will increase through the
late Friday morning hours as the gradient continues to tighten
ahead of FROPA. Southwest gusts up to 40 to 55 mph are likely
for much of the area, strongest east of the Divide. HiRes models
indicate the front to push into Yellowstone by around 4PM and
pushing southeast through the evening hours, reaching east of
the Bighorns by 6-7PM where the highest of fire weather concerns
will be. Moisture will be limited east of the Divide, but areas
around the Cody Foothills off the Absarokas will have the best
chance for precipitation with frontal passage, outside of the
upslope flow of the Bighorns to Owl Creeks/Bridgers. Minimal
high elevation snow and limited in the valley rain of
significance but around a 20 percent coverage on this occurrence
heading towards sunset Friday evening. By sunrise Saturday
morning, any shower activity will have diminished in the wake of
the cold front as this system has continued to underperform
with the models with its weaker trajectory over time this past
week. Being indicative of the winter to come in the stronger El
Nino pattern, it could be a recurring theme going forward and
especially east of the Divide.

Beyond that, temperatures Friday afternoon will push 10 to 20
degrees above average due to the suppressional heating ahead of
the aforementioned cold front. Behind it, expect more
seasonable to just below average temperatures over the weekend
into early next week to feel more Fall-like heading into the
last week of October in Wyoming. Behind this quick pushing
system into the northern Great Plains, expect induced ridging
for the later half of the weekend ahead of the next bowling ball
of a low coming from the Gulf of Alaska. By Monday morning,
expect it to reach the Pacific Northwest remaining a closed low
that will begin to affect the CWA and in particular for the west
by Tuesday. This will be more inclined for western mountain
snow and reinforcing the cooler air to allow for even some
valley snow west of the Divide. Time will tell, but models show
a disjointed system with much disagreement still to come. Stay
tuned for updated forecasts beyond this system for Friday in the
coming days.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 357 PM MDT Fri Oct 23 2026

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

MVFR conditions will become more widespread through 03Z as
showers over ID begin to push eastward. Most of these showers
will stay north of a KAFO-to-KCOD line, as the main storm system
lifts over MT. This will mainly impacting KJAC and stay north
of KBPI/KPNA. Rain will quickly end by 06Z, with clouds
scattering out through 12Z. MVFR ceilings will develop at
KBPI/KPNA and the Green River Basin by 14Z and last through 18Z.
High cirrus will push in from the southeast after 18Z, with
SCT-BKN FL120-200 skies in place over Sweetwater County/KRKS by
the end of the TAF period.

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

Winds will quickly decrease at the start of the forecast
period, dropping below 20kt by 01Z. A cold front will reach KCOD
by 02Z, turning winds northerly and bringing a chance for rain
showers through 06Z. The front will proceed southward, reaching
the remaining terminals between 04Z and 08Z. No precipitation is
expected to occur with the frontal passage at the other
terminals. Wind gusts of 20 to 25 kt will occur at all sites,
except KLND. MVFR ceilings will coincide with the front, with
these conditions lasting at KCPR, KRIW/KLND through 18Z. SKC
skies will be widespread for a few hours before high cirrus
increases from the southeast through the afternoon.

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

&&

.FIRE WEATHER...
Issued at 130 AM MDT Fri Oct 23 2026

Near critical fire weather conditions expected this afternoon
and early evening through sunset. Gusty southwest winds up to 40
to 55 mph widespread east of the Divide. Humidity values will
drop to 20 to 25 percent with the unseasonable temperatures in
the afternoon, lowest across Johnson County where a Red Flag
Warning is in effect from noon through 8PM this evening. A cold
front will push through from northwest to southeast from mid
afternoon through sunset turning winds out of the northwest but
diminish thereafter becoming 10 to 20 mph by midnight,
lingering in eastern counties through sunrise Saturday. Shower
activity west of the Divide will diminish the fire weather
concern somewhat, but still elevated due to the strong winds.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Gerhardt
DISCUSSION...Lowe
AVIATION...LaVoie
FIRE WEATHER...Lowe