332
FXUS65 KRIW 150432
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
932 PM MST Thu Nov 14 2024

.KEY MESSAGES...

- Gusty mountain winds will decrease this evening, with gusty
  winds redeveloping over southern Wyoming Friday afternoon.

- Light snow accumulations for western Wyoming valleys and
  moderate snow for mountain passes Friday evening into Saturday
  morning. Only a dusting expected east of the Divide.

- Another weather system moves through the region Monday into
  Tuesday of next week, bringing the next chance for widespread
  light snow accumulations.

&&

.DISCUSSION...
Issued at 230 PM MST Thu Nov 14 2024

The zonal flow pattern with a jet stream aloft over Wyoming
will shift to become more southwesterly overnight as a trough
develops over the West Coast. Gusty winds in the terrain will
ease overnight.

Friday will be an active weather day. By the late morning, a
shortwave rotating through the larger approaching trough will
tighten the pressure gradient over southern Wyoming, with gusty
winds in the 40 to 50 mph range expected along the I-80
corridor in southern Wyoming. These winds will be south-
southwesterly, so expect a strong crosswind component for high
profile vehicles traveling I-80.

In addition to wind, snow will be moving into the western
portions of the state by the afternoon hours. Friday evening
through the overnight hours will bring light snow accumulations
to westerly valleys. The more impactful snow amounts will be
over the mountain passes, such as Teton Pass and Togwotee Pass.
A Winter Weather Advisory is in effect for these higher
elevation travel corridors, given storm total snow
accumulations in the 4 to 6 inch range.

By daylight Saturday, precipitation rates will decrease, and
only a dusting of snow is forecast for areas east of the
Continental Divide. Temperatures will be about 10 degrees colder
than on Friday (and a few degrees below season normals) as
cooler Canadian air moves into the region.

Sunday`s temperatures moderate slightly as the region sits
between weather systems. Another trough develops over the
Pacific Northwest Sunday night into Monday, bringing the chance
for widespread light snow over Wyoming Monday into Tuesday.
Precipitation details are uncertain for this system, with a
complex jet streak forcing pattern over the CONUS. Have stuck
with consensus model guidance for the time being. Two forecast
details are fairly high confidence at this point: Cooler
temperatures about 10 degrees below seasonal normals, and gusty
north winds for the Powder River Basin on Tuesday. A ridge
quickly builds in behind the large trough deepening over the
Great Plains, leading to a dry and warming trend late in the
week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 930 PM MST Thu Nov 14 2024

High clouds, SCT-OVC FL200-250, will continue to stream over
the Cowboy state through 18Z, as a storm system moves onshore
over northern CA and progressively makes its way eastward. This
will keep winds mainly southerly or light (10 kt or less) and
variable through 18Z. Clouds will become SKC for all but western
portions after 18Z, as the cold front begins to move over
western and northern portions of the forecast area. Southerly
winds, with gusts up to 30 kt, will develop over Sweetwater
County by 17Z as a result of the gradient tightening from the
approaching front. These winds are not expected to reach KCPR,
due to a stationary front that will be lingering over southern
Natrona County. Precipitation will develop over western portions
by 22Z, most likely beginning as rain and changing over to snow
after sunset. KJAC is the only terminal expected to be impacted
by this round of precipitation, with KBPI/KPNA being impacted
after 02Z. Mainly MVFR conditions are expected with this
precipitation, although brief IFR conditions could occur (30%
chance). The cold front will quickly progress eastward passing
through central and southern portions of the forecast area
between 00Z and 06Z, reaching western portions of Natrona County
and clearing the Bighorns by the end of the TAF period.

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 2 PM Friday to 8 AM MST Saturday
for WYZ012.

&&

$$

DISCUSSION...VandenBoogart
AVIATION...LaVoie