Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 080558
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1058 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.../06Z Issuance/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

Stratocumulus with ceilings between 020-040 KFT AGL will be the main
issue through sunrise across portions of the Wind River and Big Horn
Basins. KRIW and KLND will be the terminals impacted by these low
ceilings with a chance of these clouds reaching KCOD and KWRL. There
could also be some patchy fog especially near any bodies of water.
Otherwise VFR conditions with skies becoming mainly SKC with light
winds this morning. Increasing mid-high level cloudiness is expected
to overspread the region between 21Z and 03Z as a storm system
begins to impact the western Wyoming. Winds will remain light in the
basins Thursday, but winds will be picking up from the southwest
over the mountains and in the central wind corridor from SE Fremont
County into the Casper area. Before the surface winds can respond
there could be a period of time where wind shear will be present at
KCPR Thursday evening.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

Except for patchy valley fog, expect mainly SKC conditions and light
winds this morning. However this will change rapidly Thursday
afternoon into the evening as a winter storm begins to impact the
area. Widespread snowfall is expected to breakout across west and
southwest Wyoming between 21Z and 03Z. After 03Z, Persistent MVFR
conditions with occasional IFR conditions are expected through the
night at area terminals, except for KRKS where MVFR/IFR conditions
are not expected to be more brief in nature. Mountains will become
obscured late afternoon into the early evening, and remain obscured
the rest of the night with LIFR conditions. The main exception will
be over South Pass where ceilings will be higher, and confidence for
continued snow is not as high. Turbulence over mountains will
significantly increase Thursday evening.

&&

.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...WM
FIRE WEATHER...C.Baker


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