328
FXUS65 KRIW 160817
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
117 AM MST Sun Nov 16 2025

.KEY MESSAGES...

- Some showers return to western Wyoming today, one more dry and
  mild day East of the Divide.

- Rain and mountain snow spread across the area tonight and
  Monday, with the heaviest snow expected across the western
  mountains.

- Much of next week looks cooler and potentially wetter, but
  details and timing of systems and rain and snow amounts remain
  uncertain.

&&

.DISCUSSION...
Issued at 112 AM MST Sun Nov 16 2025

It looks like the honeymoon of the unusually mild weather we
have had for the first half of November is coming to an end and
the weather will be giving us a slap back into reality. Radar is
showing some echoes across western Wyoming this morning, but
basically none are reaching the ground as of 1 am. Today
continues to look drier as guidance continues to slow the
arrival of the precipitation. As a result, we have lowered POPs
and QPF through the daylight hours. Today will be one more mild
day, especially East of the Divide which will be likely be dry
through the daylight hours. Many locations will see highs in
the 60s, likely for the last time this calendar year. A gusty
breeze will again develop across the wind corridor from Muddy
Gap through Casper, but high wind is not expected.

Precipitation will overspread much of the area between tonight and
Monday, with the steadiest and heaviest expected from midnight
through noon on Monday as the best upper level divergence and jet
support move over the state. The reasoning of the forecast
remains fairly similar to yesterday. The area of most concern
will be the Tetons where Teton and Togwotee pass have a greater
than 1 in 2 chance of 6 inches of snow or more through the
period. Given the possible impacts to travel over Teton and
Togwotee Passes, we went ahead and issued a Winter Weather
Advisory for this zone, although it was borderline. Other areas,
like the highest elevations of the Salt and Wyoming Range as
well as the western Wind River Range also have at least a 1 in 2
chance of 6 inches of snow or more. However, these are away
from the passes and with impacts expected to be limited we
elected to hold off for now. The day shift can take another look
and see if any additional highlights are needed since the
greatest impact would not be until later tonight.

This will be mainly a mountain snow event though. The 700 millibar
temperatures generally only fall to around minus 3 celsius, which
would put snow levels around 7000 feet. And this is by Monday
morning when the best lift moves out of the area. Places like
Bondurant could see a couple of slushy inches and even Pinedale
could see a slushy inch or so. The Jackson and Star Valleys
would likely only see a coating. Odds are less than 1 out of 3
for three inches in all these areas, so we will not issue any
advisories. As for East of the Divide, with 700 millibar
temperatures only falling to minus 1 celsius, snow levels should
remain above 8000 feet, with only rain for the populated areas.
There are still some disagreement on placement of the heaviest
amounts though, so we broadbrushed things for now. Most
precipitation should end from south to north starting Monday
afternoon as the upper level low moves away to the north and
east.

Cooler weather then moves in for Monday through much of next week.
However, with flow largely west or southwesterly, temperatures will
remain near to somewhat above normal through the week. Tuesday looks
mainly dry with only a few showers in northern Wyoming. Following
that, we have the same conundrum as previous days. We do look more
unsettled through the period. However, there are still large
disagreements in the guidance in regard to timing and movement of a
couple of systems moving through. So, although confidence remains
fairly high in a cooler and more unsettled pattern, details remain
highly uncertain.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 940 PM MST Sat Nov 15 2025

SCT-BKN clouds, FL150-220, continue to push northward across
the forecast area as all terminals remain VFR. An upper level
low along the southern California coast tracks inland overnight
and Sunday morning, nearing Wyoming by midday Sunday. Southerly
surface flow ahead of this feature leads to an increase in
southerly wind at KCPR and KRKS by 18Z. Isolated light showers
approach from the south over far western portions, impacting
KJAC between 14Z and 16Z and again between 19Z and 21Z.
Conditions are expected to remain VFR with these showers. Snow
levels will be around 9000 ft over the western mountains through
the day. More widespread precipitation will develop and move
over far southern portions of the state by 00Z, moving northward
through 06Z Monday. Cloud heights will lower to FL050-080
across areas west of the Divide by 00Z and continue to lower to
MVFR with the rain. KRKS and KBPI/KPNA will be impacted between
00Z and 06Z, with snow levels ranging between 7000 and 8500 ft.
This area of rain will cross the Divide and impact KCPR,
KRIW/KLND by 05Z/06Z. There is a 30% chance for LIFR
ceilings/IFR visibilities occurring with the precipitation across
most areas west of the Divide by the end of the TAF period.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 PM this afternoon to 5 PM MST
Monday for WYZ012.

&&

$$

DISCUSSION...Hattings
AVIATION...LaVoie