Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 030451
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
951 PM MST Sat Mar 2 2024

.KEY MESSAGES...

- Cold front pushing through with snow out west tapering off
  later in the evening.

- Wind east of the Divide continues this afternoon diminishing
  after FROPA towards sunset.

- Seasonable temperatures ahead with sporadic snow chances west
  of the Divide throughout the week.

&&

.DISCUSSION...
Issued at 1157 AM MST Sat Mar 2 2024

IR currently depicts ample cloud cover across the western half
of the CWA with cold cloud tops along the frontal boundary. East
of the Divide, some sporadic alto-cu with high bases ahead of
FROPA later this afternoon. Radar currently shows ample coverage
west of the Divide with the cold front distinctly seen through
Moran Junction down east of Jackson to Star Valley. The cold
front is a bit quicker and earlier than depicted with the Hi-Res
short term models. Based on the speed, FROPA looks to occur
through the Bighorn and Wind River Basins by around 2330Z and
through southern portions of the CWA by 01Z.

West of the Divide, snow rates have peaked and will begin to
dwindle through the afternoon behind the aforementioned cold
front. Brief lower visibility and heavy snowfall is occurring
along the front but has been short lived, as seen in Jackson.
Snowfall totals going forward for the remainder of the afternoon
and evening look to see an additional 3-6 inches for the western
mountains and 1-3 inches in the valleys as the snow levels have
dropped tremendously behind the front. The Winds look to see up
to a foot still as probabilistic data shows an 60-80% outlook
for 6-12 inches with FROPA still to occur. Instability wise, any
chance for thundersnow has quickly diminished behind the front
and just enough lift ahead of it as it pushed out of Idaho. Very
few lightning strikes west into Idaho prior that had the better
setup for it to occur. Lingering snow behind this main shortwave
as it exits east into the Great Plains but the low will linger
near the Pacific Northwest that will continue to pump a moisture
tongue to the western mountains, albeit much weaker with the
main finger of the PFJ well to the south now as the trough
become more elongated at its base.

East of the Divide, expect southwest winds to continually be
strong and strengthen even moreso prior to FROPA as the gradient
strengthens. With this, expect compressional heating ahead of it
allowing for temperatures to push further into the upper 40s and
even widespread 50s. This could bring enough instability to have
a possible rumble or two through the Wind River Basin and down
into Sweetwater County near the I-80 corridor, especially with
the ongoing breaks in the clouds early this afternoon. Limited
CAPE and LI indices but enough to hear a couple possible rumbles
this afternoon. Any liquid precipitation ahead of the front
will be short lived as it quickly transitions to snow behind
the front. Snowfall looks to minimal in the lower basins and
valleys and be the strongest snow rates for the Bighorns
tapering off by sunset. Behind the cold front, the gradient
slackens with decreasing divergence aloft as the upper level low
fills throughout the evening and into the overnight hours.
Lingering snow for the Winds and Bighorns and through the wind
corridor peaks overnight but limited in accumulations at this
time.

Moving forward into the long term forecast, expect a ramp up of
snow chances for the western mountains later on Sunday and into
early parts of the work week. Accumulations at this point look
to be much more modest with high confidence in this occurring,
especially with the main moisture tongue to the south of the
CWA. An additional chance Tuesday night with another shortwave
with the main trough exits Thursday morning eastward as it cuts
off into a low deep into the desert Southwest moving through
New Mexico and into Texas. Ridging then builds in for the end of
the work and into next weekend allowing for the cooler more
seasonable temperatures to improve to above average with mainly
dry conditions to occur. Longer term models indicate another
stronger system to makes its way out of the GOA towards the
Pacific Northwest that could start to show the affects for
western portions of the CWA by late Sunday of the weekend and
into the following week. Time will tell this far out but
something to keep an eye on going forward.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 951 PM MST Sat Mar 2 2024

The main weather driver through the TAF period is the exiting cold
front to the east to start the period, and then a shortwave that
moves through southern Wyoming Sunday. The shortwave through Sunday
brings snow shower chances to roughly the southern half of Wyoming.
Current models are showing a scattered nature to these showers,
making it difficult to put confidence in timing and impacts of
sites. Have put prevailing snow groups into sites where the best
chances occur, but even then, VCSH may be the prevailing weather.
KRKS looks to have the best consensus amongst models at this time.
Some models bring snow showers into the Wind River Basin, so have
included VCSH at KLND and KRIW for low confidence at this time.

Though generally not as strong as Saturday was, gusty winds return
to many sites Sunday afternoon. Some sites continue the gusty winds
tonight through tomorrow, such as Cody and Casper.

KJAC...A few snow showers linger into Saturday night, with snow
chances generally 40% or less through about 11Z/Sun. Most showers
look to remain over the mountains. A period of snow chances less
than 15% occur Sunday morning, from about 11Z/Sun to 18Z/Sun. A
shortwave moving through the southern half of Wyoming brings snow
shower chances through the afternoon and evening. Current models
have the best chances between 18Z/Sun and 05Z/Mon. Could easily see
either the chances or most likely timeframe shifting with newer
model runs, given the more showery nature of the snow and
discrepancies between hi-res models. Chances decrease Sunday
evening, with VCSH conditions returning.

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...Lowe
AVIATION...Wittmann


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