Area Forecast Discussion
Issued by NWS Riverton, WY

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734
FXUS65 KRIW 121720
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1120 AM MDT Thu Oct 12 2017

.SHORT TERM...(Today through Saturday night)
Issued at 245 AM MDT Thu Oct 12 2017

Imagery shows a broad trof/ridge pattern (west to east) across
the CONUS with WY/MT lying under/near the inflection point and WY
under swrly flow aloft. Jet (90 to 110 kts) in place in the trof
from nrn California to wrn WT and on up into Canada with a
secondary but strengthening jet to the south ovr cntrl
California/cntrl NV. An embedded small but strong shortwave
associated with the more nrn jet is currently coming through Srn
Oregon/Nrn Nevada. The SFC has a long cold front that will push
through WY today bringing light precip mainly over the nwrn
Mountains. Liquid precip through the day will only amount to a
tenth or less form most of the far nwrn portion of WY...with
associated snowfall amounts remaining under an inch. Otherwise,
today will become post frontal and dry for most of the FA with
gustiest winds (G15-30kts) west of the Divide and over the Wind
Corridor of srn/cntrl WY. Tonight winds will be gusty (G35-45kts)
in the Absaroka Mtns and nrn portions of the Cody Foothills.

Friday will see the next system enter the area with a pre-frontal
trough affecting the nwrn areas early then followed by the main
Canadian front late friday into saturday. QPF values from Friday
afternoon through Saturday morning west of the Divide will generally
range from a trace to a quarter of an inch...perhaps slightly higher
across the far northwest. This will equate with H7 temps cold enough
to snow down to the valley floors from the beginning of this event,
to generally 3 inches (nw mountains) or less. Through the rest of
the day Saturday, a secondary front of sorts looks to kick through
the FA with the upper trof axis...bringing some modest chances for
precipiation east of the Divide...including light snow or afternoon
rain/snow mixes. Snowfall accumulation, through Saturday afternoon
east of the Divide, looks to remain low at generally less than inch
inch at any given location.

.LONG TERM...(Sunday through Thursday)
Issued at 245 AM MDT Thu Oct 12 2017

Zonal flow to flat ridging is expected early next week. This will
result in dry conditions with seasonal to slightly above average
temperatures. Mid to late next week models continue to hint at
either a strong west to east Pacific Jet with a decent fetch of
Pacific moisture or a significant trough impacting the Western
U.S. Plenty of time to watch how everything evolves but will keep
Wednesday dry for now with some slight chances of PoPs Wednesday
night/Thursday across the extreme west. Otherwise temperatures
are expected to remain mainly above average with winds on the
increase.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1036 AM MDT Thu Oct 12 2017

VFR conditions will occur through the period, although hazy skies
are in place today over various locations. This was due to
Wednesday night`s cold front advecting in smoke from the ongoing
wildfires in CA and OR. A band of mid level BKN- OVC clouds
extending from KCPR- KRKS will continue to push eastward this
afternoon and into eastern WY. Otherwise, drier air and SKC
conditions will prevail across the area this afternoon. Isold to
sct -shsn and occasional mountain obscurations will return to
Yellowstone National Park early Friday morning while the rest of
the area remains VFR. Clouds associated with this precipitation
will increase southward toward KJAC through the noon hour Friday.

&&

.FIRE WEATHER...
Issued AT 245 AM MDT Thu Oct 12 2017

Today will remain seasonally cool but relatively dry with minimum
RH values in the 20s lower elevations and 30s over the mountains.
A few increasing chances for snow showers across far northwest
Wyoming through this morning. Winds will not be quite as strong as
they were Wednesday. Smoke dispersion will be good by this afternoon.
Expect winds to increase again Friday. Snow showers will increase
across the area Friday and will continue into Friday night in the
west. The snow showers will dissipate Saturday. Temperatures
Saturday will likely be the coolest that the temperatures will
get until a gradual warm up begins Sunday.

&&

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

$$

SHORT TERM...Hulme
LONG TERM...Murrell
AVIATION...LaVoie
FIRE WEATHER...Lipson



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