Kemmerer, Wyoming Weather Forecast Discussion

002
FXUS65 KRIW 011015
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
415 AM MDT Wed Oct 1 2025
.KEY MESSAGES...
- There is a 10% chance for showers across western portions and
  the central basins, with mostly dry conditions expected
  elsewhere.
- Chances for widespread low elevation precipitation and high
  elevation accumulating snowfall increase for late Friday into
  Saturday.
- Colder temperatures Saturday through Monday, with the first
  freezing temperatures to lower elevations east of the Divide
  possible Sunday night/Monday night (20 to 30% confidence).
&&
.DISCUSSION...
Issued at 103 AM MDT Wed Oct 1 2025
Southwest flow aloft will be in place over the Cowboy State today
through Friday, as a longwave trough develops off the West Coast and
gradually digs south over the Great Basin by Friday. There will be a
10% chance for showers over the western mountains today, as subtle
shortwaves move over the area through this flow. Some of these
showers could move into the central basins toward the later half of
the afternoon. Temperatures will be cooler east of the Divide, but
still slightly above normal in the lower to middle 70s. Dry and
warmer conditions will be in place Thursday, as 500mb heights build
from a 591dm high over NM as well as the trough beginning to dig
south over northern CA. This will lead to highs in the lower 80s
returning to areas east of the Divide and slightly above normal
temperatures elsewhere.
Increasing chances for showers and thunderstorms will occur over
western portions Friday afternoon, as the eastern fringes of the
storm system approach the Cowboy State. The associated cold front
will reach far northern portions of the Bighorn Basin and western
portions of the state, leading to highs in the upper 60s to near 70
degrees. Breezy conditions will occur east of this boundary, along
and east of a Rock Springs-to-Buffalo line. Elevated fire weather
conditions will occur within this area as a result of the increased
southwest winds, occurring over the Wind Corridor (Rock Springs to
Casper) Friday afternoon. Critical RH values are not expected at
this time, but there is a high likelihood of wind gusts up to 35 mph.
The cold front will progress eastward through the overnight hours
Friday night, with showers remaining possible over western portions
through the night. Snow levels will be around 9500 ft, dropping as
low as 8500 ft by 12Z Saturday. Widespread showers are expected
Saturday, as the storm system moves over the region and exits over
the Northern Plains by 12Z Sunday. Temperatures will be 15 to 20
degrees colder Saturday as a result. Windy conditions with gusts up
to 50 mph will be possible across portions of Sweetwater County and
northern portions of the Bighorn Basin, as the main trough axis
moves over eastern WY. Additionally, there is a 10% chance for gusts
up to 60 mph near Buffalo Saturday night. Snow levels could drop as
low as 7000 ft over western portions during the day Saturday, and
range between 6000 and 7000 ft across the CWA Saturday night.
Needless to say, temperatures will be much colder Saturday night
with readings in the middle to upper 20s in the western valleys.
Lows in the middle to upper 30s expected east of the Divide and
Sweetwater County.
A second system that has been progged dropping south from Canada on
Sunday is still in the forecast, however it looks to come more in
phase with the exiting storm and bring a much colder Canadian air
mass to the Cowboy State as it sweeps eastward. This could lead to a
chance for snow for far northern portions of the Bighorn Basin, like
Cody and Lovell. This would also result in snow levels dropping to
6000 ft over the Bighorns. At this point, Sunday will be a pretty
raw, fall day, with highs in the lower to middle 50s under mostly
cloudy skies. Precipitation chances will be widely scattered at this
point, as any moisture will be residual with no strong forcing
mechanisms in place. Models continue to trend toward developing a
positively-tilted trough/cutoff low over the Great Basin/northern CA
Monday. The Cowboy State could be caught in an area of weak steering
flow or a building ridge from the cutoff low. Either way,
indications continue to point toward quieter conditions early next
week.
&&
.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 410 AM MDT Wed Oct 1 2025
VFR conditions prevail through the period at all terminals. A few
showers continue across the region to start the period, mainly
in vicinity of KJAC and KPNA. We can`t rule out patchy fog in
vicinity of KJAC, KPNA and KBPI but with the chance less than 1
out of 5 we left it out of the forecast. Wind gusts past 20
knots will be possible at anytime in vicinity of KCPR and after
16Z at KRKS. All terminals have a very small chance of a shower
between 19Z and 23Z this afternoon, but with the chance only
around 1 out of 10 we kept the forecast dry. Wind should become
less than 10 knots after 03Z Thursday as the wind decouples.
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...LaVoie
AVIATION...Hattings

NWS RIW Office Area Forecast Discussion