Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 142234
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
334 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 00Z TAFS through 00Z Tuesday
Issued at 324 PM MST Sun Jan 14 2018

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

FEW-SCT clouds over NW mountains this evening. A strengthening
downslope NNE flow should hinder fog/low cloud formation vicinity
KJAC after 06Z Monday. An Arctic cold front plunging south along
the east slopes of the Divide will push southward tonight, with
increasing clouds over the mountains. This front will move across
the Interstate 80 corridor, KRKS, by 06z- 09z Monday with areas
of MVFR ceilings likely behind the front. Confidence remains low
for this to occur at KRKS. Skies are expected to clear from NW to
SE through the morning hours Monday across the area.

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

VFR conditions are expected to prevail through 00Z Monday. An
Arctic cold front will push south and west into the area tonight,
spreading primarily low MVFR ceilings and visibilities in -SN to
a vicinity KCOD-KCPR line between 03Z-06Z Monday and against the
east slopes of the Divide (KRIW-KLND) 07Z-10Z Monday. Mountains
will become increasingly obscured tonight, with the Bighorns
already mainly obscured. These conditions will persist across the
area through 12Z Monday, before the snow ends and clouds clear
from the area by 18Z Monday.

&&

.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...LaVoie
FIRE WEATHER...Baker


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