210
FXUS65 KRIW 161757
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1057 AM MST Sun Nov 16 2025

.KEY MESSAGES...

- Scattered western mountain snow and valley rain chances
  (30-60%) through the afternoon hours today, with largely dry
  conditions elsewhere.

- Rain and mountain snow chances (60-100%) spread south to north
  across the state beginning after sunset and continuing through
  mid-day Monday. The heaviest precipitation is expected during
  the early Monday morning hours.

- The upcoming week is trending to have near normal temperatures
  and be more active (40-60% chance), specifically Wednesday
  into Thursday. There remains uncertainty in exact timing as
  well as rain and snow amounts.

&&

.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 /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1057 AM MST Sun Nov 16 2025

VFR conditions persist through 00Z/Monday as southerly flow ahead of
an upper low over Nevada spreads mid and high clouds across the
region. Light showers skirt the western border in the vicinity of
KJAC Sunday afternoon. The better chance for showers arrives
over the southwest terminals between 01Z-03Z/Monday as a wave of
moisture lifts north ahead of the upper low. This initial wave
continues north to a KJAC-KRIW-KCPR line around 06Z/Monday.
Widespread MVFR is anticipated in association with this wave,
and localized IFR occurs at KRKS, KPNA, and KBPI where rain
changes to snow later tonight. The upper low tracks into
southern Wyoming by sunrise Monday with the associated 700 mb
circulation set to move across central Wyoming 09Z-15Z/Monday.
This leads to a period of enhanced precipitation before
downsloping northwest flow arrives by midday Monday. Conditions
improve at terminals west of the Continental Divide around
18Z/Monday. Widespread mountain obscurations after 03Z/Monday.

&&

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

&&

$$

DISCUSSION...Hattings
AVIATION...CNJ