Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 142115
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
215 PM MST Thu Dec 14 2017

.SHORT TERM...This evening through Sunday
Issued at 115 PM MST Thu Dec 14 2017

Tonight and Friday will be dry with areas of valley fog mainly
in the west. Clouds will increase in the northwest Friday afternoon
with strong winds along the east slopes of the Absaroka mountains
and Cody foothills.  A Pacific low pressure trough will move southeast
from British Columbia and the Pacific Northwest bringing snow and colder
temperatures to the western Mountains and valleys Friday night
with snow becoming widespread by late evening. The heaviest
snowfall will be in west central and northwest areas especially
before midnight with lighter amounts to the south in Lincoln and
Sublette counties.  Snowfall will spread east of the Continental Divide
late Friday night becoming more widespread by Saturday morning.   Snowfall
will continue in the west Saturday and spread into central and south areas
east of the Continental Divide with the heaviest snowfall in Natrona and
Fremont counties tapering off in the west Saturday evening and in the
east Sunday morning when colder Canadian air moves in with northerly
winds.

.LONG TERM...Sunday night through Thursday
Issued at 115 PM MST Thu Dec 14 2017

A weak transitional ridge will be in place Sunday night but will
move out of the area overnight allowing for a general NW upper level
flow.  This will set up a shortwave to arrive on Monday focusing
precip in the NW Mountains through much of Tuesday.  Wednesday the
low will arrive from the NW coast bringing widespread snow to WY.
Models are in a bit of disagreement at this point with GFS forming a
cut-off low over the SW US and ECMWF/Canadian deepening the trough
to our east.  The GFS and ECMWF are both leading to a direct north
flow Thursday which could lead to a very cold weekend.

&&

.AVIATION...For the 00Z TAFS through 00Z Friday afternoon
Issued at 115 PM MST Thu Dec 14 2017

VFR conditions for the rest of tonight through early morning Friday
when patchy fog is once again possible.  I am not completely sold
for fog at airfields yet as models indicating the saturation layers
are very shallow, so vicinity fog is the current forecast. Winds
will also be gusty Friday morning at KCOD/KCPR/KRKS ahead of the
next weather system. See TAFs for further details.

&&

.FIRE WEATHER...
Issued AT 115 PM MST Thu Dec 14 2017

Tonight and Friday will be dry with areas of valley fog mainly
in the west. Clouds will increase in the northwest Friday afternoon
with strong winds along the east slopes of the Absaroka mountains
and Cody foothills.  A Pacific low pressure trough will move southeast
from British Columbia and the Pacific Northwest bringing snow and colder
temperatures to the western Mountains and valleys Friday night
with snow becoming widespread by late evening. The heaviest
snowfall will be in west central and northwest areas especially
before midnight with lighter amounts to the south in Lincoln and
Sublette counties.  Snowfall will spread east of the Continental Divide
late Friday night becoming more widespread by Saturday morning.   Snowfall
will continue in the west Saturday and spread into central and south areas
east of the Continental Divide with the heaviest snowfall in Natrona and
Fremont counties tapering off in the west Saturday evening and in the
east Sunday morning when colder Canadian air moves in with northerly
winds.

&&

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

$$

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



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