Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 290517
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1017 PM MST Mon Nov 28 2016

.Short Term...Tonight Through Tuesday (Issued at 231 PM MST)

Organized snowfall quickly coming to an end in the western
mountains and not much yet east of the Continental divide outside
of the mountain areas.  As the closed upper level low pressure
center moving into Minnesota ejects east northeast through the
evening, strong northwest flow aloft will line up with the Bighorn
mountains significantly increasing the flow over northern Johnson
county. Have upgraded High wind watch to a high wind warning for
tonight and Tuesday. Some light snow showers will linger over and
near the mountains in the northwest flow with colder temperatures
moving in.

.Long Term...Tuesday Night Through Monday

Cold northwest flow will gradually shift to the east as a high
pressure ridge aloft shifts east into western Wyoming.  General
clearing will occur while some low stratus may linger over and
near the mountains. Overall wind will decrease. A Pacific low
pressure trough will approach the western mountains Wednesday
afternoon increasing through the night with some warming east of
the Continental Divide as clouds increase.  A cold front will
move south from Montana on Thursday with light snow spreading
across the central and east as cold air moves in. Snowfall
amounts in the cold air look very limited but some places along
the north and east facing mountain slopes may see 1c to 3 inches
of light fluffy snow. This will start a rather prolonged cold
spell which will be hard for the valleys and basins to recover
from as temperature inversions will develop and the cold dense air
will be hard to scour out of the lower elevations. Will likely
need to add areas of fog to the forecast but am more concerned
with snow amounts at this time. Friday looks rather benign with
Wyoming between troughs and high pressure in place. Temperatures
will likely be the biggest forecast challenge. Friday night and
saturday a Pacific low pressure trough will move towards northwest
Wyoming from Northern Idaho and Western Montana with light
snowfall spreading across the west and north. This will keep some
light snow over the mountains through Saturday night but moisture
looks very limited and cold air will remain trapped in the
valleys and basins. The flow aloft is expected to shift from the
northwest to west with a flat ridge. Moisture will increase into
the west ern mountains Sunday afternoon and Sunday night with a
warmer source region. Moisture content should increase with more
productive snowfall resulting. Windy areas will increase across
the south and east. Snowfall amounts could be significant Sunday
night and Monday as a trough deepens to the west of Wyoming with a
continued favorable moisture plume. Winds across the south and
east could get quite strong ahead of a cold front moving south
from Montana.

.Aviation.../06Z Issuance/

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

Some snow showers over and near the mountains will continue
through Tuesday evening. Expect some mountain obscuration
along with MVFR to IFR conditions in the vicinity of the
mountains. The terminal sites will maintain VFR conditions
through the forecast period.

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

VFR conditions will occur at the terminal sites through the
period. A gusty wind will be common in northern WY through
Tuesday afternoon. The wind will gradually decrease Tuesday
night. Some snow showers will occur in the Bighorn mountains
through 18Z, then become isolated snow showers after 18Z.
Expect mountain obscuration at times with MVFR/IFR conditions
through 21Z. Snow showers will be ending after 01Z Wed.

.Fire Weather...

Organized snowfall quickly coming to an end in the western
mountains and not much yet east of the Continental divide outside
of the mountain areas.  As the closed upper level low pressure
center moving into Minnesota ejects east northeast through the
evening, strong northwest flow aloft will line up with the Bighorn
mountains significantly increasing the flow over northern Johnson
county. Have upgraded High wind watch to a high wind warning for
tonight and Tuesday. Some light snow showers will linger over and
near the mountains in the northwest flow with colder temperatures
moving in. The basins and valleys will have inversions in place
with poor smoke dispersal. The windy areas of the east will have
good smoke dispersal on Tuesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 11 PM this evening to 5 PM MST Tuesday
for WYZ010.

&&

$$

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



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