808
FXUS65 KRIW 250911
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
211 AM MST Mon Nov 25 2024

.KEY MESSAGES...

- Mainly dry and seasonable today with a gusty wind continuing
  around Casper.

- The next Pacific system brings light to moderate snow to much
  of western and central Wyoming from late tonight through
  Tuesday night.

- Seasonably chilly from Wednesday through the holiday weekend
  with only occasional light snow showers possible.

&&

.DISCUSSION...
Issued at 207 AM MST Mon Nov 25 2024

We are now transitioning into the holiday season, with people
getting ready to make journeys to indulge in turkey, stuffing and
all the fixings and pass out in front of football games due to the
large amount of tryptophan. And attention this week turns to holiday
travel. The news is mostly good in this department as 6 of the next 8
days looks good. However, this is Wyoming and you know we are going
to have a fly in the ointment somewhere.

For the most part, today looks mainly quiet with transitory
shortwave ridging moving over the Cowboy state, bringing dry
weather and temperatures near normal. There are two minor concerns
today. The first is the fog monster emerging from his lair to feast
on the moisture from the snow yesterday. He has already arrived
in Kemmerer. The other area of concern is Casper with the snow
showers yesterday. It would last long today though. With the pressure
gradient tightening ahead the next Pacific trough and cold front,
southwest wind will again increase from Muddy Gap through Casper.
The 700 millibar winds do not look sufficient for high wind, topping
out at around 35 knots on most guidance. Probabilistic guidance
shows only a 1 in 4 chance of gusts over 45 mph except in the higher
elevations. So, it will be windy but nothing unusual for the area
for late November.

The next Pacific system then approaches the area late night and will
spread some snow from south to north across mainly southern and
western Wyoming through Tuesday night. As for timing, most guidance
shows the steadiest snow occurring during the day Tuesday,
especially Tuesday afternoon with the passage of the trough axis.
One change here from the last system is that the best forcing will
be south of the area across Colorado, so the highest amounts of
snow would fall in the Salt and Wyoming Range and Star Valleys,
not further north. Amounts in some areas are borderline for
advisories. However, given the possible impact for holiday
travel, we have issued winter weather advisories for western
Wyoming. For guidance, we have used the 2 out of 3 chance in the
probabilistic guidance for 2 inches of snow or more in the
lower elevations and 1 out of 2 for 6 inches or more in the
higher elevations. We did give some thought for one for
Sweetwater County given the impacts to Interstate 80 but held
off for now. The day shift can reevaluate this. As for snow East
of the Divide, there could be some snow showers but the chance
for an inch of snow at any spot East of the Divide is less than
1 out of 10. Any snow would hold off here until Tuesday so still
time to take another look at things. Snow will gradually taper
off Tuesday night as the system moves away.

High pressure should then bring mainly dry weather for Wednesday.
Following this, things look mainly dry through much of the holiday
weekend. There will be a couple of weak systems in the form of
Alberta Clippers that will approach the area. The first will
approach on THanksgiving Day. This system has little moisture to
work with, it looks almost as dry as the turkey in the Christmas
Vacation movie so any snow showers with it would be scattered and
any accumulations light, probably less than an inch. The second then
approaches Friday or Saturday. There is more spread in the models
here so details are hard to come by but like the previous system,
has little moisture to work with. Each system will bring some cooler
Canadian air to drop temperatures somewhat. Temperatures will be
below normal, especially Thursday and Saturday, but nothing unusual
for late November. The main quiet weather also looks to continue as
we move into the 1st of December as well.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1037 PM MST Sun Nov 24 2024

VFR conditions are expected to prevail at terminals as the previous
system has pushed out of the area. There is some concern for some
fog at KCPR tonight through the post sunrise hours given the fresh
snow and clearing skies there. However, a southwest breeze is
expected to pick up over the next few hours, likely hindering any
fog development. Otherwise, KCPR will see the southwest wind
increase further during the afternoon. Elsewhere, wind will remain
on the lighter side. Clouds will begin to increase late in the
period ahead of the next system that will move in to western Wyoming
early Tuesday morning.

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 from 11 PM this evening to 5 AM MST
Wednesday for WYZ012-013-023-024-027.

&&

$$

DISCUSSION...Hattings
AVIATION...Myers