Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 150620
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1120 PM MST Sun Jan 14 2018

.SHORT TERM...This evening through Wednesday
Issued at 114 PM MST Sun Jan 14 2018

A Canadian cold front moving south from Montana will move south
across the Big Horn basin, Johnson, Natrona and Fremont counties
and surrounding mountains tonight with light snow becoming more
widespread through the evening. Snowfall is expected to range
from 1 to 3 inches with up to 5 inches in the mountain areas.
Colder temperatures will move in behind the cold front as well.
Slick, snow packed and icy roads can be expected through Monday
morning.  Snowfall will taper off through morning ending by noon.
In the west colder and rather dry north northwest flow will remain
tonight and Monday. Fog in the valleys likely to continue with
inversions in place and limited mixing. Expect it to remain dry
through Tuesday with an increasing chance of snow showers coming
in from the west southwest Tuesday night and Wednesday.

.LONG TERM...(Wednesday night through Sunday)
Issued at 114 PM MST Sun Jan 14 2018

Conditions will be dry at the beginning of the forecast period, as a
transitory ridge moves over the region by 12Z Thursday. Timing of
precipitation reaching the far west continues to be pushed back, as
the longwave trough digs as it makes its way onshore over the PACNW.
SW flow aloft will usher in this next round of precipitation, with
chances increasing across NW portions and the western mountains
through the day Thursday.  A cold front associated with this system
will quickly pass through the forecast area through the day Friday.
As it does so, strong winds may be possible in wind prone locations,
like the Wind Corridor. Scattered PoPs from morning snow/afternoon
rain/snow and rain will occur east of the Divide along and behind
the front. This will be brief ahead of the front, as temperatures
drop below freezing behind the front and continue as snow Friday
night. With the jet bringing in plenty of Pacific moisture and
associated dynamics, western portions could receive a healthy dose
of fresh snow Thursday night through Friday. Snow will gradually end
Friday night into Saturday, from northwest to southeast, as another
transitory ridge and a somewhat zonal flow pattern take shape
Saturday and Sunday. Apart from warming that could occur Thursday,
temperatures will be near to slightly below normal through the rest
of the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1118 PM MST Sun Jan 14 2018

West of the Continental Divide...KJAC, KBPI, KPNA and KRKS

MVFR ceilings and patchy fog vicinity KJAC is expected to improve
10z-13z as downslope NE flow dry lower levels out and erode
inversions.  An Arctic cold front pushing down the east slopes of
the Divide is expected to move into SW Wyoming, vicinity KRKS, 10z-
12z, with a NE wind shift and some MVFR ceilings developing mainly
north and east of KRKS.  Skies will clear with drier air and
increasing NE winds later in the morning.  Clear skies are expected
to prevail over the area Monday afternoon and Monday night, with
patchy fog developing vicinity KJAC and KBPI a few hours after
sunset.


East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL

A band of -SN with MVFR, local IFR ceilings and visibilities, was
pushing southwest vicinity of a KCPR-KWRL-KCOD line at 06z, with the
back edge of this band and clearing vicinity KBYZ-KGCC.  This band
of light snow will continue to push SW and dissipate overnight as it
moves through KRIW-KLND.  The back edge (clearing skies) should be
near a KCOD-KCPR line at 15z, and through KRIW-KLND by 18z.  Clear
skies and light wind will then prevail Monday afternoon and Monday
night.

&&

.FIRE WEATHER...
Issued AT 114 PM MST Sun Jan 14 2018

A Canadian cold front moving south from Montana will move south
across the Big Horn basin, Johnson, Natrona and Fremont counties
and surrounding mountains tonight with light snow becoming more
widespread through the evening. Snowfall is expected to range
from 1 to 3 inches with up to 5 inches in the mountain areas.
Colder temperatures will move in behind the cold front as well.
Slick, snow packed and icy roads can be expected through Monday
morning.  Snowfall will taper off through morning ending by noon.
In the west colder and rather dry north northwest flow will remain
tonight and Monday. Fog in the valleys likely to continue with
inversions in place and limited mixing. Expect it to remain dry
through Tuesday with an increasing chance of snow showers coming
in from the west southwest Tuesday night and Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Baker
LONG TERM...LaVoie
AVIATION...Meunier
FIRE WEATHER...Baker



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