783
FXUS65 KRIW 212342
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
442 PM MST Thu Nov 21 2024

.KEY MESSAGES...

- Ridging provides tranquil and warm conditions for most of
  western WY the next couple days.

- The remnants of the PacNW trough sweep across the state late
  Friday through early Sunday, with mountain snowfall.

- Unsettled pattern continues into next week, with colder
  temperatures.

&&

.DISCUSSION...
Issued at 103 PM MST Thu Nov 21 2024

H5 ridge continues to deflect most weather away from Wyoming
today, giving a boost to autumn temperatures. The ridge will
remain in place through most of tomorrow, bringing another day
of highs in the 40s and 50s, with lows in the 20s and 30s east
of the Divide and in the teens to the west. The southwesterly
flow over the ridge is still clipping far NW WY, providing
light snow flurries for greater YNP and areas north of Jackson.
This feed will continue to provide light snow in those areas
again tomorrow, but intensity remains light so accumulations
won`t account to much this round.

The upper low off the PacNW coast continue to sit and spin this
afternoon. This will start to fall apart piece by piece starting
today, but the overall trough remains in place off the coast.
The first piece of the trough will impact local weather late
Friday through Sunday morning. Since this trough will be only a
small part of the whole, energy coming along for the ride will
be limited, keeping the strength of the system lowered. Also
latest runs keep the main energy to the north and west into
Idaho and Montana. So the main impacts on WY will be limited to
the western mountains and YNP Saturday. As the trough and
associated cold front sweep through Saturday night/Sunday, a
round of snow will develop along the southern edge of the
trough. Currently this focuses on Sweetwater and Natrona
County, with the possibility of 1 to 2 inches of fresh snow for
those locations.

A zonal flow pattern setups up behind this trough for the first
half of next week. The PacNW trough will still be in place, so
some Pacific moisture will get fed into this flow. This would
bring some light snow accumulations to west-facing ranges,
depending on how much moisture is able to get across the west
coast mountain ranges and reach farther inland.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 441 PM MST Thu Nov 21 2024

High pressure will keep mostly quiet weather across the region
for the next several days. A weak shortwave will move through
overnight, increasing cloud cover for most terminals. Cigs will
be at 150 to 200ft AGL through the rest of the TAF period. This
shortwave will also bring slight chances (30 to 40%) of snow
showers to KJAC overnight. Snow showers will mainly exist over
the mountains, with mountain obscurations existing through the
period, but could see some of those showers make their way to
the valley floor with best chances between 07Z and 11Z Friday
morning. Clouds gradually begin to scatter out Friday afternoon.

Winds remain mostly light (less than 10kts) at all terminals with
the exception of KCPR, where a southwest wind will persist through
the period. The wind will diminish slightly overnight, but remain at
12 to 18kts, then increase again Friday morning with gusts 25 to
30kts during the afternoon.

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...Straub
AVIATION...Hensley