524
FXUS65 KRIW 231521
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
821 AM MST Sun Feb 23 2025

.KEY MESSAGES...

- Occasional strong winds up to 70 mph for the Absaroka
  Mountains and Cody Foothills today into tomorrow.

- Gusty winds in excess of 50 mph for the Wind Corridor (roughly Rock
  Springs to Casper) today. Outer Drive in Casper sees gusts in
  excess of 60 mph.

- Snow moves into western mountains late this morning. Western valleys/basins
  may see rain or rain/snow mix. Heaviest mountain snow occurs
  this afternoon through tomorrow morning.

- Warmer weather over the next several days brings ice jamming
  and flooding concerns to the northern Bighorn Basin due to
  current snowpack there.

&&

.UPDATE...
Issued at 820 AM MST Sun Feb 23 2025

Not much to update this morning. Models still on track with bringing
snow to the western mountains starting the latter half of this
morning. Heaviest snow will be this afternoon into tomorrow morning.
Winds over the Absarokas and Cody Foothills have been up to 60 mph
so far this morning. These occasional strong gust have been making
it to the Cody/Clark area.

Temperatures are also expected to warm up today east of the Divide.
Will be monitoring rivers for possible ice jamming or flooding
impacts in the northern Bighorn Basin as the snowpack there begins
to melt over the next several days.

&&

.DISCUSSION...
Issued at 1150 PM MST Sat Feb 22 2025

IR currently depicts clear skies across the CWA with high clouds
pushing in from the west spilling over the ridge. The main
shortwave is evident across the Pacific northwest that will push
through the state Sunday through Tuesday. Upper level ridging
has begun to break down as it pushes east into Sunday morning
due to increasing divergence aloft with the aforementioned next
disturbance. The main finger of the PFJ continues to slide
further south through Montana towards northern Wyoming that will
start to pump in the Pacific northwest moisture, and thus the
increasing snow chances.

As this shifts further south, the gradient and zonal flow
increases mixing to the surface come Sunday morning. Ongoing
drainage wind for the Cody Foothills and Wind River Basin
overnight but all areas will see a rise in wind speeds by mid to
late morning with daytime heating. The wind corridor will see
its usual higher wind speeds, although not the most ideal high
wind warning criteria direction but still seeing frequent 50
plus mph winds. The main energy to see the higher speeds will be
across the Absarokas and into the Cody Foothills, where 60 to 70
mph gusts will be likely into the afternoon and overnight into
Monday. Some easement of winds overnight but will remain
elevated at all locations. Snow chances will increase out of
Idaho by late morning for Yellowstone and into the western
mountains by early afternoon. Valleys will not see the
precipitation until mid afternoon, but at that point, a mix to
even just liquid rain will be the likely type with the warmer
than average temperatures above freezing. Turning over to snow
after dark overnight into Monday will give way to minimal
accumulations with the best chances for 2 to 3 inches at 70 to
80 percent. Southern Yellowstone and the Tetons/Gros Ventres
will see 60 to 80 percent accumulation`s over 8 inches with
Tetons the best chances for over a foot of 40 to 50 percent.
This is all per usual for the westerly zonal upper level flow
but with more minimal amounts across the western Winds to the
Salts/Wyoming ranges at this time. Winter weather headlines will
remain in place for the aforementioned areas being the more
prevalent a bit further north in line with the main finger of
the PFJ.

Otherwise, snow diminishes overnight Monday into Tuesday as well
as the higher winds with the main shortwave pushing east of the
Divide and out of the CWA by day`s end into Wednesday morning.
Frontal passage Tuesday afternoon will hinder the high
temperatures by a few degrees, especially east of the Divide
with only minimal chances for some sprinkles and/or flakes but
mainly dry for most outside of the higher terrain. Ice jamming
and any flooding concerns look to be more limited with this
system for the northern Bighorn Basin and Johnson County with
the FROPA and looks to be more aligned for concerns later into
the work and next weekend. A stronger ridge looks to build in
Wednesday onward with increasing convergence aloft bringing
another more distinct warming trend and dry conditions. This
will help to aid in blocking a closed low well to the south and
limit the impacts of the next system by the end of next weekend
where precipitation chances increase once again. Time will
tell, so stay tuned for updated forecasts in the coming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 330 AM MST Sun Feb 23 2025

Prevailing VFR conditions through this morning. A weather
system moves in from the northwest by Sunday afternoon brining
snow/rain to KJAC by 20Z. The heaviest snow/rain will begin
around 22Z at KJAC with conditions dropping to IFR by that time.
Conditions are expected to deteriorate further at KJAC by 02Z
as ceilings drop to IFR (possibly as low as LIFR) Sunday
evening. Lower ceilings move into KBPI and KPNA after 06Z
Monday.

Wind will be the story at other terminals as strong wind develops at
KCPR/KCOD this afternoon. Gusts as high as 50 knots will be
possible at times Sunday afternoon at these terminals. Mountain
obscuration will increase across western mountain ranges Sunday
afternoon, becoming prevalent Sunday evening.

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...
Winter Weather Advisory until 11 AM MST Monday for WYZ001-012.

High Wind Warning until 5 PM MST Monday for WYZ002-003.

&&

$$

UPDATE...Wittmann
DISCUSSION...Lowe
AVIATION...Hattings