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FXUS65 KRIW 180938
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
238 AM MST Fri Jan 18 2019

.SHORT TERM...Today through Sunday night

Snow has become light and is now mainly over southern portions of
the forecast area this morning. These showers will gradually end, as
light snow over the far west becomes steady. Light snow will also be
possible over Johnson and Natrona counties later this morning after
sunset. Otherwise, the rest of the area will be mainly dry today, as
the flow over WY turns more NNW. These winds will turn more WNW into
Saturday, as a broad ridge develops over the Northern Rockies. This
will bring a warm advection pattern of snow to far western portions,
with steady light snow occurring through the day Saturday. Winter
weather advisories could be possible for the Jackson and star Valley
areas. This activity will taper off to flurries/very light snow
Saturday night into Sunday. The best chances for accumulating snow
Sunday will be over Yellowstone and the Bighorns. By Sunday night,
models prog another digging trough over portions of the Great Basin.
This could bring another round of moderate to heavy snow to
southwest portions (similar to Thursday night) early Monday morning.
Temperatures look to finally moderate and continue through the
weekend, allowing the basins and valleys that have been trapped to
finally mix out. Also, there is no strong intrusion of cold/arctic
air that will occur today or Friday. Thus, temperatures should be
closer to normal on Saturday and Sunday. Gusty winds will also
continue over the Wind Corridor through Sunday and develop over the
Absarokas and Wind River Mountains.

.LONG TERM...Monday through Thursday night

A weather system moves through the region Monday and exits the
area late Mon night. Snow continues for the mountains with a
chance of light snow for the lower elevations. Snow amounts look
to be 1 to 3 inches in the lower elevations with 4 to 8 inches in
the mountains. The snow decreases Mon night and ends by daybreak
Tue for most places. On Tuesday, it will be dry for the lower
elevations. Some light snow will develop in the NW WY mountains
Tuesday afternoon. The snow will increase in the west Tuesday
night. The next weather system moves into the area Wednesday and
out of the region Thursday morning. Snow is likely for the
mountains again with scattered areas of snow at the lower
elevations. Any lingering light snow on Thursday morning would be
ending by late morning. Then dry Thursday afternoon and night.
High temperatures Mon through Thursday will be seasonal with 20s
and 30s for the most part with teens and 20s in the mountains.

&&

.AVIATION...For the 12Z TAFS through 12Z Saturday

West of the Continental Divide (KJAC, KRKS, KPNA, KBPI)

Widespread MVFR, areas of IFR conditions will decrease early this
morning with ceilings gradually lifting, snow decreasing through 15z
Friday. Further north, scattered to numerous snow showers will
linger mainly over the mountains with frequent mountain
obscurations. A drier westerly flow and VFR conditions will then
prevail across southwest Wyoming Friday afternoon, with surface
west wind 20-30 kt and gusty prevailing along the I80 corridor.
These winds will decrease shortly after sunset. Light to moderate
snow and widespread MVFR conditions, areas of IFR conditions,
will move back into far western Wyoming, vicinity KJAC-KEVW, 09z-
12z Saturday.

East of the Continental Divide (KCPR, KCOD, KRIW, KWRL, KLND)

Areas of fog vicinity KCOD should erode, as a drier westerly flow
pushes down into the area. Lower IFR/LIFR ceilings and light snow
was also pushing down the east side of the Bighorn Range KSHR-
KBYG, but these lower ceilings are not expected to make it south
to Casper. Additionally, snow showers pushing east along the I80
corridor are expected to remain south of a KLND-KCPR line through
Friday morning. Drier air will push west to east across the area
Friday afternoon. VFR conditions are expected to prevail 00z-12z
Saturday.

&&

.FIRE WEATHER...

Light to moderate snow will continue over southern portions this
morning. Light snow will continue over the western mountains today
and through the weekend. Gusty west winds will continue over
southern portions today. Gusty southwest winds will return over
the Wind Corridor Saturday. Another significant snow event is
slated for Sunday night and Monday. Lighter accumulations are
expected east of the Divide from this next event.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

Winter Weather Advisory until 11 AM MST Friday for WYZ001-002-
013>015-025-026-028>030.

Winter Storm Warning until 11 AM MST Friday for WYZ012-023-024-
027.

&&

$$

SHORT TERM...LaVoie
LONG TERM...AR
AVIATION...Meunier
FIRE WEATHER...LaVoie
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