084
FXUS65 KRIW 221919
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1219 PM MST Wed Jan 22 2025

.KEY MESSAGES...

- Scattered snow showers across the Bighorns and northern
  Johnson county.

- Next system pushes in early Friday and overnight into the
  weekend.

- Warming trend and dry conditions expected next week.

&&

.DISCUSSION...
Issued at 1154 AM MST Wed Jan 22 2025

IR currently shows the shortwave out of Montana into northern
and northeastern portions of the state with WV showing the broad
ridging through the west and jet dipping down from Canada and
into Colorado through the southern Great Plains. Radar shows
some sporadic snow showers across the Bighorns with light snow
for northern Johnson and points north into Montana. This will be
the main focus of the remainder of the day as gusty north to
northwesterly winds over 30 to 40 mph allow for blowing/drifting
snow (even though light) but with snow already on ground. This
will create some sporadic limited visibilities for the I-90/I-25
corridors east and north from Buffalo. Points south should
remain relatively dry, although a stray snow shower could push
off the southern Bighorns with a low chance/confidence in an
isolated snow band/squall at this point in time. Winds further
south from Buffalo to Kaycee and Casper are a bit light but
still with frequent gusts up to 25 to 30 mph to create this
concern during "peak" heating of the afternoon. Otherwise, hi-
res models are indicating some of the light snow off the
Bighorns/Bridgers will push into the eastern Wind River Basin
after sunset with minimal accumulations expected through about
9 to 10PM. Low probabilities even for a tenth (<5% for RIW,
around 20% for LND) being just enough possible to dust over the
plowed/shovels roads/sidewalks....Around a 40-50 percent chance
for 4 or more inches for the higher terrain of the far northern
and southern Bighorns, while the passes a 80-90 percent of 1-2
inches. Combined with the wind, this could still pose a limited
threat, and thus keeping the advisories going overnight into
early Thursday morning.

A more northerly upper level flow for Thursday as brief and
broad ridging pushes in exiling the main finger of the PFJ to
the north and east. No concerns for the day but ahead of the
next system for early Friday morning. The upper level pattern
becomes more meridional as diffluence aloft deepens a trough
over the Pacific northwest. With a more northwesterly flow,
Pacific northwest moisture will pump into the CWA early Friday
morning giving way to increasing snow chances northwest/west to
southeast/east throughout the day. A cold front will drop
through with the shortwave north to south Friday morning into
the early afternoon hours. More consensus with a number of the
models indicating an earlier FROPA than expected being more
progressive with its movement. As such, snow amounts have come
down a bit with a widespread inch or two for many of the Basins
for the entire CWA with higher terrain up to 4 to 6 inches the
best educated guess at this point in time. In all, the snow
impacts in terms of accumulations look to be limited. However,
the wind ahead of FROPA due to the tightening gradient and quick
switch in direction behind it, may cause some impacts, although
limited not seeing any indications of higher wind gusts.
Regardless, winds diminish behind the front through the
afternoon and evening hours into the weekend.

Some lingering snow showers into Saturday morning being more
curtailed to Sweetwater and far southern Natrona counties into
the afternoon and evening hours. The EC, that has been handling
best in the longer term solutions, cut the low off across the
souther Desert with west to east oriented ridging across much of
the northern Rockies. As the aforementioned low pushes across
the southern plains to the east, ridging builds formidably
across much of the western US. This will give way to dry
conditions and a warming trend for much of next work week. Above
average above freezing temperatures could be had for some east
of the Divide but time will tell in the coming days along with
how much snow is actually received Friday into Saturday. Long
term models don`t show the next possible system until the next
weekend, so enjoy next week if comes into full fruition.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1038 AM MST Wed Jan 22 2025

A broad trough digs into the Great Plains, with the edge of the
trough clipping WY this afternoon, bringing northerly winds and
chances for snow showers, mainly east of the Continental Divide,
during the late afternoon and evening. VFR conditions are expected
to prevail at all terminals.

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

Snow showers will occur with the trough passage, however, there is
low confidence (30%) in direct impacts to any terminals. Most likely
timing of the snow showers is generally between 00Z and 06Z this
evening. MVFR conditions are expected with the snow showers. Mid-
level cigs around FL040-FL080 will occur through the afternoon with
cigs dropping to MVFR with any snow showers. Skies look to clear
quickly after 06Z, with SKC at most terminals by 12Z Thursday.

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

Gusty northwest winds will persist at KBPI and KPNA with gusts to
near 25kts through much of the period, decreasing late in the
period. Otherwise, mostly clear skies will exist through much of the
period. SCT to BKN FL080 decks could develop this evening, but will
clear out quickly. There is a slight chance (10%) of low clouds or
fog at KJAC between 11Z and 15Z Thursday, but confidence is too low
to include in the TAF.

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 5 AM MST Thursday for WYZ008>010.

&&

$$

DISCUSSION...Lowe
AVIATION...Hensley