Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 172000
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
100 PM MST Fri Nov 17 2017

.SHORT TERM...(This evening through Monday)
Issued at 1230 PM MST Fri Nov 17 2017

A Pacific low pressure trough over the Northern Rockies and
Northern Great Basin will pass to the east of the western
mountains of Wyoming through the evening bringing a significant
decrease in Pacific moisture as the upper level flow shifts to
the northwest and colder air moves in.  The threat of heavier
snowfall will end early in the evening in the evening shifting
to areas east of the Continental Divide.  Rain will be mixed
with the snow in the evening changing to all snow as the
temperatures cool.  Some clouds and lighter snowfall will
linger over the mountains and east with clearing late tonight
and Saturday morning. Strong winds aloft behind the Pacific low
pressure trough may surface along the east slopes of the
mountains with the highest winds in the Cody foothills and the
Upper Wind River Basin bringing a threat of high winds around
Clark and Dubois. The threat of high winds will begin late this
evening and continue into early Sunday morning.  Temperatures
will be the coldest of the season Tonight through Saturday night
with gradual warming Sunday and Sunday night.  Dry conditions will
extend into Monday before the leading edge of Pacific moisture
ahead of another Pacific low pressure trough reaches the west
Spreading snow into the western mountains again Monday afternoon.
Windy conditions will continue along and east of the east slopes
of the mountains and through the wind corridor from the vicinity
of Rock Springs through Casper.

.LONG TERM...Monday night through Friday
Issued at 1230 PM MST Fri Nov 17 2017

Shortwave overriding the ridge to our west Monday night.  Most of the
precip looks to be west of the divide with snow falling in most
areas and isolated areas of rain in the south.  Most should be done
by mid day Tuesday though some snow may linger in the Western
Mountains through Wednesday. Thursday will have turkey, pies,
football, and high pressure ridging so Thanksgiving should be a
pretty nice day.  Most of Friday should remain decent due to
continued ridging. However, Friday evening the models get a little
conflicted.  The Canadian is rushing in a deep trough across
Wyoming with pretty strong precip trends across the state. GFS and
ECMWF both weaken the ridge a bit allowing for a front to drape
across the northwest corner of the state.  For now I am going with
the GFS and ECMWF as they are closest to agreement and keeping most
of the evenings weather in the west.

&&

.AVIATION...For the 00Z TAFS Saturday through 00Z Sunday
afternoon) Issued at 1230 PM MST Fri Nov 17 2017

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals

The weather system exits to the east around midnight. Periods of
snow will continue occur into late evening in the valleys and
mountains though much more isolated. MVFR conditions are still
expected across the KBPI/KPNA area with the mountains frequently
obscured. Conditions will improve in the after 06Z with VFR
conditions prevailing. A gusty wind will occur at KRKS for most of
this TAF period. Please see individual terminal forecasts for more
details.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

VFR conditions to prevail tonight. Scattered rain and snow showers
will occur today into the late evening. MVFR condition will occur
due to lower ceilings and vsbys. A gusty wind will be common in many
locations with the wind decreasing after 03Z. KCOD will be the
exception, gusting 25 to 30kts through the night and into tomorrow.
VFR conditions will prevail over the region after 06Z.

&&

.FIRE WEATHER...
Issued AT 1230 PM MST Fri Nov 17 2017

A Pacific low pressure trough over the Northern Rockies and
Northern Great Basin will pass to the east of the western
mountains of Wyoming through the evening bringing a significant
decrease in Pacific moisture as the upper level flow shifts to
the northwest and colder air moves in.  The threat of heavier
snowfall will end early in the evening in the evening shifting
to areas east of the Continental Divide.  Rain will be mixed
with the snow in the evening changing to all snow as the
temperatures cool.  Some clouds and lighter snowfall will
linger over the mountains and east with clearing late tonight
and Saturday morning. Strong winds aloft behind the Pacific low
pressure trough may surface along the east slopes of the
mountains with the highest winds in the Cody foothills and the
Upper Wind River Basin bringing a threat of high winds around
Clark and Dubois. The threat of high winds will begin late this
evening and continue into early Sunday morning.  Temperatures
will be the coldest of the season Tonight through Saturday night
with gradual warming Sunday and Sunday night.  Dry conditions will
extend into Monday before the leading edge of Pacific moisture
ahead of another Pacific low pressure trough reaches the west
Spreading snow into the western mountains again Monday afternoon.
Windy conditions will continue along and east of the east slopes
of the mountains and through the wind corridor from the vicinity
of Rock Springs through Casper.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST this afternoon for WYZ001-
002-013-015.

Winter Storm Warning until 5 PM MST this afternoon for WYZ012-
014-023-024.

High Wind Warning from 11 PM this evening to 5 AM MST Sunday for
WYZ003-016.

&&

$$

SHORT TERM...Baker
LONG TERM...Hulme
AVIATION...Hulme
FIRE WEATHER...Baker



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