213
FXUS65 KRIW 212306
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
506 PM MDT Fri Mar 21 2025

.KEY MESSAGES...

- The next weather system moves across Wyoming tonight into
  Saturday, bringing snow to western Wyoming valleys and the
  mountains. Winter Weather Advisories are in effect for western
  Wyoming.

- Strong and gusty winds during the daylight hours Saturday.
  High Wind Warnings cover the areas most impacted, where gusts
  55 to 65 mph are looking likely (90% chance).

- Very warm next week, with temperatures warming to 15 to 20
  degrees above normal for Wednesday and Thursday.

&&

.UPDATE...
Issued at 200 PM MDT Fri Mar 21 2025

High clouds have thinned this afternoon but increasing moisture
and cloud cover are expected as the evening progresses, with the
next weather system and snow arriving this evening for western
mountains shortly after sunset. Western Wyoming snow is
currently forecast to be most intense in the 3 AM to 10 AM
window. Winter Weather Advisories are in effect to cover this
hazard. Several short term weather models show snow becoming
more showery in nature (in other words, "hit-or-miss" or "on-
and-off") after noon Saturday, but these brief showers could be
intense and quickly lower visibilities for a short while each.
Snow ends for most locations across western Wyoming by 3 to 4
PM.

Areas east of the Divide will receive minimal precipitation
with this system, and any light precipitation with the front
should be rain or quickly melting snow given afternoon
temperatures in the 40s for most.

Winds remain on track to become strong and gusty shortly before
sunrise Saturday with gusts 40 to 50 mph by the afternoon for
most areas. In central Wyoming, gusts 50 to 60 mph will be
common, with wind prone areas having the possibility of gusts up
to 70 mph. High Wind Watches have been upgraded to Warnings for
the windiest areas.

&&

.DISCUSSION...
Issued at 253 AM MDT Fri Mar 21 2025

Most shower activity has swept east overnight, following along
with the shortwave. A couple light showers remain in the BYG
vicinity, but should be complete by sunrise. Northwest flow will
bring some very light orographic snowfall to western mountains,
but likely only an inch or so before sunset. Brief ridging
ahead of the next system will bring another mild day across the
state, wit highs in the 40s and 50s, with gradually increasing
clouds aloft.

The next quick-moving shortwave will race across the state
tonight and Saturday, bringing another round of snow for the
western mountains and adjacent valleys. Latest models runs look
slightly quicker in both arrival and end of snow, with initial
upswing mid evening tonight lasting through mid-afternoon
Saturday. With the speed of the passing wave, and the increasing
strength of the now-springtime sunshine, the final accumulation
totals have nudged down a bit, but are still within range of
Winter Weather Advisories. The snow will sweep east of the
divide during the day, but accumulations in these areas will be
further hindered by warm ground temperatures melting any
accumulation, along with daytime temperatures being high enough
for rain/snow mix.

This system will also bring stronger low level winds along for
the ride, with around 50kt jet at H7. This will be enough to mix
some gusty winds to the sfc at the most prone areas in central
WY. Have hoisted a High Wind Watch for the Green Mountains and
lower elevations of Natrona County. If any snow is able to
accumulate briefly on Saturday east of the divide, the gusty
winds may cause some localized blowing and drifting snow
briefly. This whole system departs quickly, with all precip
finished by the end of Saturday. Another round of quick
orographic snowfall increases Sunday night, but would only
produce an inch or two mainly for YNP.

Models are similar on a very dominant early spring ridge
building across the Intermountain West for the upcoming week.
Ensembles are agreeing on widespread 50s and 60s returning by
Monday, with the peak of the ridge bringing some 70s across
central Wyoming by Wednesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 506 PM MDT Fri Mar 21 2025

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals

VFR conditions prevail across all terminals for the start of the TAF
period but a incoming disturbance will begin to move into western WY
early Saturday morning. Snow begins to move back in across all
western terminals shortly after 05Z Saturday with KJAC having the
best chance of periodic MVFR to IFR conditions. Winds increase early
Saturday morning for all terminals with widespread gusts of 20 to 30
knots by sunrise. Gusty winds develop by the late morning on
Saturday with westerly wind gust of 30 to 40 knots at times. As
winds begin to increase across the area precipitation will become
more showery in nature with many terminals going from prevailing
light snow to light snow showers. The majority of snow showers will
dissipate by the early afternoon on Saturday with strong gusty winds
prevailing into the end of the TAF period. Frequent mountain
obscuration is expected through nearly all of the TAF period.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

VFR conditions are expected to prevail across all terminals through
the TAF period. A weather system will move into western WY this
evening with precipitation to remain mainly west of the Divide.
Winds gradually decrease for the start of the TAF period with KCPR
seeing a brief lull before winds increase by the early morning hours
Saturday. Winds are forecast to become gusty to strong for all
terminals by the early to mid morning on Saturday. Strong gusty
winds are likely at times through the end of the TAF period
especially at KCPR, KCOD, KRIW, and KLND. Overall, frequent wind
gusts of 30 to 45 knots will be possible across nearly all east of
the Divide terminals by the late morning on Saturday. Isolated gusts
of 50 knots cannot be ruled out for most terminals especially KCPR.
Along with the arrival of these strong gusty winds will come the
chance for some light showers mainly at KCOD and KCPR. Mountain
obscuration is expected after 06Z Saturday and will gradually spread
east remaining in place through the TAF period.

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...
Winter Weather Advisory until 6 PM MDT Saturday for WYZ001-
012>014-023-024.

High Wind Warning from 3 AM to 9 PM MDT Saturday for WYZ019-
020.

&&

$$

UPDATE...VandenBoogart
DISCUSSION...Straub
AVIATION...Dziewaltowski/Rowe