Area Forecast Discussion
Issued by NWS Riverton, WY

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642
FXUS65 KRIW 071958
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1258 PM MST Wed Dec 7 2016

.Short Term...Tonight Through Thursday

Cold high pressure will be over western and central Wyoming
tonight and Thursday morning. Temperatures will be cold with lows
to -25 in the west valleys and -15 in the south and central
basins. some low stratus and patchy fog will be found in the
valleys and basins. Some flurries or ice crystals will also
be observed in the cold air.  Thursday afternoon clouds will
move into the west with areas of light snow developing over the
mountains.  west to southwest winds will also pick up across
the south and west and along and near the east slopes of the
mountains and across eastern Sweetwater...southern Fremont and
Natrona counties.  The windy areas will see temperatures warm
significantly.

.Long Term...Thursday Night Through Wednesday

Snow...clouds and wind will increase across the west Thursday
evening with areas of moderate to heavy snow developing along with
blowing and drifting snow. Winter Storm watches are in effect
for the western mountains and valleys Thursday afternoon through
noon Saturday.  There is potential for another strong Pacific jet
to set up bringing a deep moist plume of pacific moisture into the
west through Saturday 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. Some snow will linger over the west
on Wednesday with clearing south...central and north with colder
temperatures.

&&

.Aviation.../00Z Issuance/

Winds will be mainly light through the forecast period. This evening
skies are expected to become mostly clear with the main concern
being the potential for fog development at most valley locations
since boundary layer moisture will be high, light winds, and some
warming aloft allowing surface inversions to strengthen. Any fog
should burn off tomorrow by around 17Z in most locations except for
the deeper valleys. Clouds will increase in the west tomorrow as a
Pacific system heads toward the area but any MVFR or IFR conditions
or precipitation should hold off until after 00Z Friday.

&&

.Fire Weather...

Cold high pressure will be over western and central Wyoming
tonight and Thursday morning. Temperatures will be cold with lows
to -25 in the west valleys and -15 in the south and central
basins. some low stratus and patchy fog will be found in the
valleys and basins. Some flurries or ice crystals will also
be observed in the cold air.  Thursday afternoon clouds will
move into the west with areas of light snow developing over the
mountains.  west to southwest winds will also pick up across
the south and west and along and near the east slopes of the
mountains and across eastern Sweetwater...southern Fremont and
Natrona counties.  The windy areas will see temperatures warm
significantly. Winds are expected to be rather light with an
unimpressive pressure gradient expected tonight. 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...
Winter Storm Watch from Thursday afternoon through Saturday
morning for WYZ001-002-012>015-023>025-027.

&&

$$

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



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