Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 210513
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1013 PM MST Mon Feb 20 2017

.Short Term...Tonight Through Thursday (Issued at 141 PM MST)

In the west...Southwest flow aloft with a deep pineapple
connection moisture plume entering western Wyoming will continue
to produce periods of moderate to heavy snow with strong winds at
ridge top and pass level. Prolonged periods of 2 inch an hour
snowfall is expected. Temperatures will cool Tuesday night with a
gradual decrease in snowfall into Wednesday morning. Winter storm
warning will remain in effect until early wednesday morning.
Tetons still look good for a 30 inch snowfall while the rest of
the western mountains should be in the 15 to 25 inch range.
Valleys still look warm enough for mainly rain to rain snow mix
until Tuesday evening when temperatures cool and precipitation
should change over to snow for the last 12 hours of the storm.
Some light snow will continue with low accumulations Wednesday and
Wednesday night with much colder temperatures. Some very spotty
light snow can be expected over the mountains with partial
clearing and cold temperatures on Thursday.

In the East...Strong west to southwest winds aloft will shift
south with high winds developing across Fremont and Natrona
counties this afternoon, continuing through Tuesday night. Strong
winds also impact the Lander Foothills and Hot Springs County
through Tuesday night. Wednesday night and Thursday a cold front
will sweep south from Montana with much colder temperatures and
northeast upslope winds producing rather widespread light snow.
The heaviest snowfall expected in the Casper and Lander areas.

.Long Term...Thursday Night Through Monday

Upslope snows will be winding down across Central Wyoming as the Colorado
low becomes more organized over the Central Plains with the asct energy
gradually sliding off to the east. Another 1 to 3 inches of snowfall could
fall from the Lander Foothills and surrounding mtns to Casper and Casper
Mountain Thursday night. A secondary trough following the main exiting
trough axis will keep light snowfall going across the rest of the CWA
Thursday night through Friday night before the focus once again shifts to
Western Wyoming Saturday once a more progressive westerly Pacific flow
reestablishes itself and increasing snowfall gets underway out west through
next weekend. From Saturday through Monday expect dry weather east of the divide.
Temperatures will be around 10 degrees colder behind Thursdays
troughpa with highs mainly in the 20s and lows in the single digits and teens.

&&

.Aviation.../06Z Issuance/

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

Snow in the mountains through Tuesday night with IFR/LIFR conditions.
Rain and snow mixed in the western valleys through 00Z Wed, then
all snow through Tuesday night. Expect MVFR to IFR conditions at
times. KRKS will remain VFR through Tuesday night.

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

VFR conditions will prevail at the terminal sites through Tuesday night.
A strong wind will occur at the KCPR airport through 00Z Wed, then
gradually decrease. Gusty wind will occur at some of the other terminal
sites through 00Z Wed. LLWS will also occur at a few terminal sites
through 00Z Wed. Please check the latest terminal forecast for more
details.

&&

.Fire Weather...

In the west...Southwest flow aloft with a deep pineapple
connection moisture plume entering western Wyoming will continue
to produce periods of moderate to heavy snow with strong winds at
ridge top and pass level. Prolonged periods of 2 inch an hour
snowfall is expected. Temperatures will cool Tuesday night with a
gradual decrease in snowfall into Wednesday morning. Winter storm
warning will remain in effect until early wednesday morning.
Tetons still look good for a 30 inch snowfall while the rest of
the western mountains should be in the 15 to 25 inch range.
Valleys still look warm enough for mainly rain to rain snow mix
until Tuesday evening when temperatures cool and precipitation
should change over to snow for the last 12 hours of the storm.
Some light snow will continue with low accumulations Wednesday and
Wednesday night with much colder temperatures. Some very spotty
light snow can be expected over the mountains with partial
clearing and cold temperatures on Thursday. Smoke dispersal will
be poor through Thursday.

In the East...Strong west to southwest winds aloft will shift
south with high winds developing across Fremont and Natrona
counties this afternoon, continuing through Tuesday night. Strong
winds also impact the Lander Foothills and Hot Springs County
through Tuesday night. Wednesday night and Thursday a cold front
will sweep south from Montana with much colder temperatures and
northeast upslope winds producing rather widespread light snow.
The heaviest snowfall expected in the Casper and Lander areas.
The windier areas will see fair to good smoke dispersal in the
afternoon Tuesday with poor smoke dispersal Wednesday and
Thursday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

Winter Storm Warning until 5 AM MST Wednesday for WYZ001-002-012-
014-015-024.

High Wind Warning until 11 PM MST Tuesday for WYZ005-018>020.

&&

$$

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



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