258
FXUS65 KRIW 140919
AFDRIW

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

.KEY MESSAGES...

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

- Showers 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 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 to 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 of 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, bring 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 /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 951 PM MDT Mon Oct 13 2025

Low clouds continue at KCOD (IFR) and KWRL (MVFR) this evening and
will persist through Tuesday morning. At KCOD there is a chance
(30%) for light freezing drizzle tonight until just after sunrise.
Scattered rain showers are pushing in from the south and west this
evening and will impact KJAC early Tuesday morning. PROB30 groups
remain at KRKS, KRIW, KLND, and KBPI. Chances (40-50%) are high
enough for prevailing light rain at KPNA tonight into Tuesday
morning.

Temperatures will remain warm enough for precipitation to remain all
rain at terminals where precipitation chances are meaningful. This
is excluding KCOD where the low clouds may produce some light
freezing drizzle at times as temperatures are already below freezing
at the terminal. Overall wind will be light overnight, but will
become breezy late Tuesday morning through Tuesday afternoon at KRKS
and KCPR. Where wind will be above 6 knots it will generally be from
the south as the weather system as a whole remains west of the area
Tuesday. Conditions will greatly improve late Tuesday morning at
terminals impacted by low clouds and rain, but low clouds should
return at KCOD and KWRL Tuesday night.

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

&&

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

&&

$$

DISCUSSION...Hattings
AVIATION...Rowe