Riverton, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

334
FXUS65 KRIW 221118
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
418 AM MST Sun Dec 22 2024

.KEY MESSAGES...

- Increasing snow chances for the western mountains now through
  Monday. Winter Weather Advisory in Effect for the Tetons.

- Next weather system moves to the south Christmas Day, but may
  bring brief light snow to western Wyoming.

- Areas of Wyoming east of the Divide remain dry and mild for
  the latter half of December.

&&

.DISCUSSION...
Issued at 201 AM MST Sun Dec 22 2024

Light snow has begun to fall across the western mountain this
morning, but precip has been light and minimal so far. The main
portion of the first shortwave trough is already passing by to
the north across Montana, so only light snow continues for the
western mountains today, mainly fueled by orographic lift. The
next trailing trough is moving ashore along the PacNW Coast, and
should be bringing increased moisture by this evening to western
WY. While moisture is still only modest, enough mountain lift
will be available to bring modest snow amounts again to the
western mountains. This snow will continue into the day Monday
as the trough moves through before decreasing Monday evening.
Snow totals for the Tetons remain steady at 8 to 12 inches, with
6 to 8 inches for the Salts and Wyomings and the greater Gros
Ventres. Winter Weather Advisories remain in effect through
Monday evening for the Tetons.

Unfortunately for a pattern like this, getting any moisture over
the mountain ranges into the central WY plains will be unlikely,
and will also be counteracted by westerly downsloping bringing
warmer temperatures. The system will help bring down temps
somewhat, but highs still reach the 40s, with some localized
warmer temperatures just off mountain ranges.

Expect a brief lull between systems on Tuesday, just enough to
get the the jolly fellow and his herd of flying Rangifer
tarandus into the state to make his yearly rounds. The next
shortwave sweep by to the south pre-dawn Christmas morning, but
will be just close enough to bring another round of light snow
to the western mountains.

Still not much to speak of beyond Christmas weather-wise, with
models keeping fast zonal flow going through the rest of the
week. This would keep light snow continuing along the western
mountains, but only light amounts, and keeping temperatures
mild east of the Divide.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 415 AM MST Sun Dec 22 2024

Weak disturbances aloft are beginning to move across the
Intermountain west and influence the weather and flight conditions
at multiple terminals through the TAF period. At KJAC, southwesterly
winds with gusts less than 20 kts are expected over the next few
hours with light snow all day. Ceilings are forecast to lower around
18Z with impacts beginning around 21Z. Expect IFR visibilities
through at least 04Z and MVFR ceilings through Monday morning;
however, brief periods of IFR visibilities after 04Z cannot be ruled
out.

At KBPI and KPNA, confidence is high in fog development after 03Z.
There is an 80% chance of MVFR fog at KPNA and an 80% chance in IFR
fog at KBPI. Confidence in IFR fog at KPNA is much lower (around
30%) so kept MVFR fog at this time. Fog at these terminals will
persist through the rest of the TAF period. Expect windy conditions
at KCPR, KCOD, and KRKS today with gusts around 25 kts beginning
between 18-19Z at KCOD and KRKS and diminishing shortly after
sunset. Winds at KRIW are forecast to increase after sunset to above
10 kts. Otherwise, at all other terminals, winds will generally be
less than 10 kts.

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 7 PM MST Monday for WYZ012.

&&

$$

DISCUSSION...Straub
AVIATION...Gerhardt