Area Forecast Discussion
Issued by NWS Riverton, WY

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449
FXUS65 KRIW 062032
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
132 PM MST Tue Dec 6 2016

.Short Term...Tonight Through Wednesday

A short wave low pressure trough now over Idaho and southwest
Montana now spreading clouds and areas of light mountain snowfall
into western and northern Wyoming will continue to move southeast
tonight across west and southwest Wyoming...then into northwest
Colorado ending up in southeast Colorado by Wednesday morning
spreading areas of light snow across western and central Wyoming
tonight and Wednesday tapering off in the afternoon from
northwest to southeast. The clouds and precipitation will moderate
temperatures...especially in the western valleys that dipped to
-25 to -35 overnight. Lows are expected in the -10 to -20 range
tonight in the west with zero to -10 east of the continental
divide. Snowfall rates should be low producing a low density
fluff. Accumulations of 1 to 2 inches are expected with 3 to 5
inches in and near the mountains. Winds are expected to be rather
light with an unimpressive pressure gradient expected tonight and
Wednesday. Highs are expected to range from the lower teens in the
east to -5 in the western valleys.

.Long Term...Wednesday Night Through Tuesday

With the low moving away from the area and clearing expected
Wednesday night...areas of fog are expected in the valleys and
basins with colder low temperatures. -15 to -25 may be common in
the western valleys with zero to -10 east of the Continental
Divide. A Pacific low pressure trough will move into the west
coast Thursday with the leading edge of moisture moving into the
western mountains in the afternoon. Areas of light mountain snow
will develop. There is potential for another strong Pacific jet
to set up bringing a deep moist plume of pacific moisture into the
west through Saturday night with potential very significant
snowfall in the western mountains and valleys and another strong
wind event east of the Continental divide. Temperatures will warm
from thursday through Saturday. Saturday night and Sunday a cold
front should move south east of the Continental divide spreading
snow to the area and bring another shot of cold air into the
region. Decreasing snow with partial clearing is expected on
Sunday and Sunday night with windy conditions across the south and
areas along and near the east slopes of the mountains and through
the wind corridor from eastern Sweetwater...southern Fremont and
Natrona counties.  Snow will quickly return to the west on Monday
as yet another Pacific low pressure trough and jet with another
significant moisture plume from the Pacific moves into western
Wyoming with potential significant snowfall Monday thorough
Tuesday in the west and north.

&&

.Aviation.../00Z Issuance/

A quick moving upper wave, and a reinforcing cold front combine for
increasing cloudiness and some snowfall in many areas this evening
and tonight. The best coverage and duration of snowfall is expected
over Sweetwater County including RKS terminal where MVFR conditions
are expected to develop by 01Z and last through much of the period.
MVFR to Low VFR ceilings are expected to develop across much of the
area east of the Divide shortly after sunset with some
flurries/light snow especially in favored upslope areas such as
CPR/LND. There will be some mountain obscurations as well,
especially East of the Divide. Conditions should improve after 12Z
Wednesday from west to east as the wave moves away from the area.

&&

.Fire Weather...

A short wave low pressure trough now over Idaho and southwest
Montana now spreading clouds and areas of light mountain snowfall
into western and northern Wyoming will continue to move southeast
tonight across west and southwest Wyoming...then into northwest
Colorado ending up in southeast Colorado by Wednesday morning
spreading areas of light snow across western and central Wyoming
tonight and Wednesday tapering off in the afternoon from
northwest to southeast. The clouds and precipitation will moderate
temperatures...especially in the western valleys that dipped to
-25 to -35 overnight. Lows are expected in the -10 to -20 range
tonight in the west with zero to -10 east of the continental
divide. Snowfall rates should be low producing a low density
fluff. Accumulations of 1 to 2 inches are expected with 3 to 5
inches in and near the mountains. Winds are expected to be rather
light with an unimpressive pressure gradient expected tonight and
Wednesday. Highs are expected to range from the lower teens in the
east to -5 in the western valleys. Very low mixing heights with
light to calm winds will produce poor smoke dispersal through
Thursday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...C.Baker
LONG TERM...C.Baker
AVIATION...Hattings
FIRE WEATHER...C.Baker



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