668
FXUS65 KRIW 141752
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1152 AM MDT Tue Oct 14 2025

.KEY MESSAGES...

- A bit warmer today with showers becoming less numerous through
  the afternoon.

- Shower coverage increases again Wednesday into Thursday, with
  the highest precipitation amounts in northwestern Wyoming.

- Snow is likely in the mountains starting Wednesday afternoon,
  as snow levels fall from 9000 feet to around 7000 feet.

&&

.DISCUSSION...
Issued at 316 AM MDT Tue Oct 14 2025

The overall framework of the forecast remains intact this morning,
although there are a few tweaks to the details. We do have a few
areas of showers with a bit of embedded lightning moving north
across the area as I write this. On the balance though, today looks
like the least active day of the next three. Most models are in
agreement in showers becoming less numerous as the shortwave
bringing these showers moves away to the north. There will still be
some around, but most areas should end up mostly dry most of the
time. The most numerous showers still look to be across western
Wyoming. And with the southerly flow, temperatures should be a bit
warmer than yesterday, especially East of the Divide where there
should be increasing amounts of sunshine through the day.

Things begin to become somewhat more active later tonight and into
Wednesday as the upper level low, now located near the California
coast, begins to move onshore and toward the Great Basin.
Precipitation still largely looks more intermittent Tuesday night
into Wednesday morning, with more widespread showers moving in
during the afternoon hours. The question yesterday was the track
of the upper level low as it moved over Wyoming. Model guidance
has come into better agreement as to the timing of the low,
with it crossing from Wednesday night through Thursday
afternoon. There is also somewhat better agreement in the timing
of the ending of the precipitation, with most ending by
Thursday night. However...

There is still some question to the ultimate track of the low. We
still have about an 150 to 200 mile difference in this as it moves
over Wyoming, exiting anywhere from Powell to Newcastle. This
track will still favor western Wyoming with the highest
precipitation regardless of the track. We will discuss amounts
in the next paragraph. There is more uncertainty East of the
Divide though, as portions of the area would likely end up in
the dry slot of the low, limiting amounts. And there continues
to be a spread in the models as to where this would set up. The
best chance would be across southern Wyoming, but how far north
and west the dry slot can get is still up for debate. So,
confidence is fairly high on a decent amount of QPF in western
Wyoming, but confidence drops substantially further east.

Now our thoughts on precipitation amounts. The highest amounts still
look to be across northwestern Wyoming, where there is nearly a 100
percent chance of a quarter of an inch or more of QPF, with a
greater than 1 in 2 chance of over three quarters of an inch of QPF.
Most areas East of the Divide have at least a 2 in 3 chance of over
a quarter of an inch of QPF. However, the chance of a half an inch
is generally less than 1 out of 2. And now on to the colder form of
QPF, how much snow may fall. Through Wednesday morning, amounts look
to remain small, since southerly flow should keep snow levels fairly
high, with 700 millibar temperatures of 1 celsius keeping snow
levels above 9000 feet. As the low passes and an associated cold
front moves through, 700 millibar temperatures fall to minus 3, snow
levels should lower to around 7000 feet. As for highlights, it still
looks like borderline advisory for now. The NBM ensembles give
around a 1 in 2 chance of 6 inches of snow or more in portions
of the Tetons, Absarokas and Wind Rivers, but this is mainly
above 9000 feet. The chance of a foot or more is at most 1 out
of 4 and restricted mainly to the southern Absarokas where
impacts are slim to none. We still have time to decide on
highlights since impacts to roads would likely hold off until
after sunset on Wednesday afternoon. As for the wind concern,
there will be some gusty wind on Wednesday but the chance of
gusts over 40 mph is at most 1 out of 3 and largely in
unpopulated areas.

The extended looks uncertain as well, especially Friday night and
Saturday. Some models show one last shortwave / cold front moving
into the area from Montana, bringing some showers with it.
Other guidance have mainly dry conditions. There is agreement
for Sunday though, with ridging bringing dry and mild conditions
to most of the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1152 AM MDT Tue Oct 14 2025

MVFR ceilings are expected (60-80% confidence) to dissipate around
20Z at KCOD and KWRL. IFR to MVFR ceilings are forecast (40-70%
chance) again tonight at KCOD and KWRL as well as at KRIW, KLND, and
JAC. All other terminals generally have a 10% to 30% chance of MVFR
ceilings and where chances are slightly higher, FL035 groups were
added. At KRKS and KCPR gusty winds around 20-25kts are forecast
until 01Z/02Z.

Scattered showers spread south to north across western Wyoming after
sunset this evening, with impacts possible at KJAC and KPNA as early
as 02Z. There is a 20% chance in a shower or thunderstorm at KRKS
all through the TAF period but given the low chances, opted to not
include in TAF. MVFR flight conditions could accompany any rain
showers. Shower and even a few thunderstorms generally spread to all
other terminals around the end of the TAF period. However,
confidence in direct impacts are less than 30% so there is no
mention in TAF 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...Gerhardt