116
FXUS65 KRIW 121045
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
345 AM MST Wed Feb 12 2025

.KEY MESSAGES...

- Dangerously cold temperatures across the Cowboy State
  Wednesday and Thursday morning, especially across western WY
  and portions of the Bighorn Basin.

- Strong gusty winds are possible from Casper to Rock Springs Thursday
  afternoon through Friday morning.

- A Pacific weather system moves into the region Thursday
  afternoon bringing moderate to heavy snowfall across western
  WY and light snowfall for southern WY.

&&

.DISCUSSION...
Issued at 143 AM MST Wed Feb 12 2025

Morning lows on Tuesday were cold and frigid especially across the
Bighorn Basin. Locations that have a solid snow pack saw some frigid
temperatures such as Greybull with minus 23, Clark with minus 26,
and Cody with minus 18. These locations along with Jackson Hole,
Star Valley, and the upper Green River Basin look to once again see
frigid temperatures Wednesday and Thursday morning. Guidance
supports this with most of these locations having a 40-70% chance of
seeing lows at or colder than minus 20. The remainder of the CWA
east of the Divide is not expected to see nearly as cold
temperatures due to the lack of snowpack. Forecasted low
temperatures will still be cold ranging from zero to minus 10. Due
to the increased likelihood of seeing temperatures near minus 25
Cold Advisories are in effect for western valleys and portions of
the Green River through Thursday morning. The Bighorn Basin has a
Cold Advisory in effect starting Wednesday evening through Thursday
morning. These locations will likely see wind chill values ranging
from minus 25 to minus 35 on Wednesday and Thursday morning.

Wednesday will be on the colder side across nearly all of the CWA
with highs well below normal. Current forecasted values range from
the teens to single digits and even below zero is some colder parts
of the state. The next weather maker looks to arrive by Thursday
afternoon. The setup looks to be a deep trough that digs across the
western CONUS. The bulk of the energy will remain well to the south
of the state. However, there still looks to be good chances for snow
mainly across western and southern WY. Southern WY is going to see
light snow develop during afternoon Thursday and continue into
Friday morning. Guidance is not showing big impacts but much of the
area will likely seeing a coating to 1 inch of snow (30-60%).
Southwestern WY has the better chance of seeing more than 1 inch of
snow with current guidance suggesting a 40-70% chance. Westerly flow
will keep moderate to heavy snowfall across western WY through much
of the weekend leading to the greatest accumulations among western
mountains. Lower elevation basins in western WY look to see periods
of snowfall as well with guidance showing a 40-70% chance of seeing
4 or more inches of snow. Lower elevations may need winter
highlights as well but at this time confidence is not high enough to
warrant any. However, Winter Storm Watches have been issued for
western mountains from the Salt River/Wyoming ranges to the
Tetons/Gros Ventre and southwestern YNP. Models are in good
agreement that these higher elevations will see favorable flow and
moisture to produce heavy accumulating snow. Guidance shows these
locations having a 50-80% chance of seeing a foot or more of snow.
The remainder of the CWA will likely see little to no impacts from
this system. Models are starting to show the possibility for some
light snow showers in parts of the central and northern CWA as the
system moves to the east over the weekend with very minimal impacts.

One thing to monitor ahead of this upcoming system will be the
possibility for strong gusty winds Thursday evening into Friday
morning. Models show a pretty potent jet setup across portions of
central WY with 700 MB winds of 55 to 65 knots. The greatest area of
concern will be along the Wind Corridor from Casper to Rock Springs
where guidance shows a 40-70% of seeing gusts of 50 or more mph.
Winds decrease during the day with breezy conditions lingering
through the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 345 AM MST Wed Feb 12 2025

VFR conditions at all locations through the entirety of the
period. Some very patchy fog around RIW/LND/RKS for the first
couple of hours but limited in any visibility restrictions
5-6SM. Otherwise, improving skies scattering out into the
afternoon with light winds for most locations. RKS will see 25kt
gusts after 17Z with daytime heating from the west through 03Z.
COD will see the westerly gap flow as depicted with the FV3
after 06Z with 25kts gusts for the remainder of the period into
Thursday morning. Dry conditions expected this period with
increasing snow chances into the next TAF cycle Thursday morning
west of the Divide.

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 Storm Watch from Thursday morning through Saturday
morning for WYZ001.

Cold Weather Advisory from 8 PM this evening to 10 AM MST
Thursday for WYZ003-004-006.

Cold Weather Advisory until 10 AM MST Thursday for WYZ012-013-
023-025-026.

Winter Storm Watch from Thursday morning through Saturday
afternoon for WYZ012-024.

&&

$$

DISCUSSION...
AVIATION...Lowe