Area Forecast Discussion
Issued by NWS Riverton, WY

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091
FXUS65 KRIW 030601
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1101 PM MST Fri Dec 2 2016

.UPDATE...

Winter storm watch issued for portions of far northwest Wyoming
for Sunday into Monday morning. Details to follow in the morning
package discussion.

06Z aviation discussion inserted below.

&&

.PREV DISCUSSION... /issued 114 PM MST Fri Dec 2 2016/

Short Term...Tonight Through Saturday

High pressure will be over western and central Wyoming tonight
with cold air in the valleys and basins with patchy fog expected.
A Pacific low pressure trough will dig southeast from the Idaho
panhandle and northwest Wyoming Saturday with snow moving into the
northwest spreading south and east through the day. Winds will
increase along and near the east slopes of the mountains east of
the Continental Divide. Strong winds will increase along the east
slopes of the Absaroka and Wind River mountains...the Cody
Foothills and the upper Wind River basin around Dubois. Then winds
will pick up through the wind corridor across eastern
Sweetwater...southern Fremont and Natrona counties. The windy
areas will see significant warming while the basins will remain
cold with patchy morning fog.

Long Term...Saturday Night Through Friday

The snow will increase across the western mountains with snow
also spreading east into the Bighorn mountains. Strong winds will
continue along and near the east slopes of the mountains east of
the Continental Divide...along the east slopes of the Absaroka
and Wind River mountains...the Cody Foothills and the upper Wind
River basin around Dubois. Then winds will also blow through the
wind corridor across eastern Sweetwater...southern Fremont and
Natrona counties. A stronger trough will bring more significant
snowfall to the western mountains Sunday and Sunday night with
winds remaining rather strong east of the Continental Divide
until a cold front sweeps south from Montana late Sunday night and
Monday with the chance of snow increasing across the Bighorn Basin
eastern Johnson county...the Wind River basin and Natrona county.
Colder air will come south behind the cold front remaining in the
basins into mid week. Patchy fog will continue to be a threat in
the valleys and basins. Partial clearing with high pressure moving
in will bring lighter winds Monday night and Tuesday. Snowfall
will develop again over the western mountains Tuesday afternoon
and evening as another Pacific low pressure trough approaches from
the west. Wednesday and Thursday look dry with high pressure.
Temperatures will be on the cold side with light winds. Thursday
night snow will again move into the western mountains and is
expected to increase on Friday with windy areas east of the
Continental Divide with warming in the windy areas.

Aviation.../06Z Issuance/

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

Considerable mid-high level cloudiness at times, but VFR and dry
conditions will occur. Windy westerly surface flow will occur in the
wind corridor of SE Fremont into Natrona County including KCPR
terminal, Cody Foothills, and around Dubois area.

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

The far western valleys will be impacted by persistent MVFR ceilings
and/or Visibilities in light snow by around 12Z today, possibly
improving to low MVFR conditions early tonight as the coverage of
light snow decreases. Mountains across the far west will be
obscured much if not all of the time with LIFR conditions over
mountain passes. Farther east/southeast into the Upper Green River
Basin into Sweetwater County little or snowfall is expected with
mid/high level cloudiness. Breezy westerly wind will occur at KRKS
terminal. Sounding suggested some low-level clouds or fog
developing early Saturday night at KRKS, but boundary layer looks
to be too mixed for either one.

Fire Weather...

High pressure will be over western and central Wyoming tonight
with cold air in the valleys and basins with patchy fog expected.
A Pacific low pressure trough will dig southeast from the idaho
panhandle and northwest Wyoming Saturday with snow moving into the
northwest spreading south and east through the day. Winds will
increase along and near the east slopes of the mountains east of
the Continental divide. Strong winds will increase along the east
slopes of the Absaroka and Wind River mountains...the Cody
Foothills and the upper Wind River basin around Dubois. Then
winds will pick up through the wind corridor across eastern
Sweetwater...southern Fremont and Natrona counties. The windy
areas will see significant warming while the basins will remain
cold with patchy morning fog. The windy areas will have good smoke
dispersal with deeper mixing while the cold valleys and basins
will remain trapped with poor smoke dispersal Saturday afternoon.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late Saturday night through Monday
morning for WYZ001-012-013.

&&

$$

UPDATE...WM/JB
SHORT TERM...C.Baker
LONG TERM...C.Baker
AVIATION...Skrbac
FIRE WEATHER...C.Baker



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