Area Forecast Discussion
Issued by NWS Riverton, WY

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780
FXUS65 KRIW 241655 AAA
AFDRIW

Area Forecast Discussion...UPDATED
National Weather Service Riverton WY
1055 AM MDT Sun Sep 24 2017

.SHORT TERM...Today through Tuesday night
Issued at 230 AM MDT Sun Sep 24 2017

The upper low at the base of the longwave trough is currently over
western/southwestern UT this morning. This low will slowly make its
way toward SW WY through the day today, before making its way over
central WY by 12Z Monday. By this time, the low will begin to fill
and finally exit the area by 00Z Tuesday. The CWA will be in a
somewhat COL area Tuesday and Tuesday night.

Light precipitation will continue across the area this morning.
Areas of light to moderate rain will occur over SW portions this
morning, as the low makes it way toward NE UT. By 18Z today,
precipitation over central portions will intensify with bands of
moderate rain through the afternoon. Precipitation will weaken and
decrease over the area through the overnight hours Sunday, as the
low fills. Isolated showers will remain possible through the day
Monday, mainly affecting the Absarokas, Bighorns and Wind River
Mountains. Snow levels are expected to stay above 6000 feet,
averaging around 6500 to 7000 feet, today through Sunday night. 1
to 2 inches will remain possible in the lower elevations, with an
additional 3 to 5 inches in the mountains.

.LONG TERM...(Wednesday through Sunday)
Issued at 230 AM MDT Sun Sep 24 2017

Wednesday looks dry with milder temperatures. On Thursday the GFS
brings in some moisture to southern WY due to a weather system
near the four corners. The ECMWF model is in a similar location
Thursday with the weather system, but keeps the moisture just
south of WY. Have gone with isolated showers and storms in
southern Sweetwater county Thursday afternoon and night. Dry
weather over the rest of the region Thursday along with milder
high temps. This weather system is forecast to weaken Friday as
it passes through WY per the GFS model. The ECMWF model keeps the
upper system around the four corners Friday and it never moves
into WY. Have kept isolated showers in the far south Friday. The
rest of the area will be dry Friday with mild high temps. On
Saturday and next Sunday the ECMWF model keeps the weather dry
with mild high temps for late September. The GFS model hints at
isolated showers in the western mountains Saturday as a weak
weather system passes through the region. Have added isolated
showers for Saturday afternoon but confidence is low that this
will even occur. Otherwise, dry weather for most areas next
weekend with the mild temps.

&&

.AVIATION...For the 18Z TAFS through 18Z Monday Issued at 1055 AM
MDT Sun Sep 24 2017

West of the Divide...KBPI/KJAC/KPNA/KRKS Routes

An extensive deck of low clouds east of the Continental Divide will
cut off sharply right along the divide. However, there will be
areas of MVFR/IFR/mtn obscn west of the divide with the asct low
clouds and precip (mainly snowfall) circulation around the low
currently over the vcnty of Manila, Utah. The lowest cigs and vsby
will be concentrated closet to the path of this low which will track
northeast across Farson and South pass through tonight, and then
east of the Divide Monday. Isolated thunderstorms are also possible
today. Improving conditions are expected Monday with some lingering
MVFR conditions as the storm system exits east.

 East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Routes

An extensive deck of low clouds covers almost the entire forecast
area east of the divide and cuts off sharply right along the
Continental Divide. Extensive IFR/mtn obscn with some MVFR
conditions, mainly due to low cigs, will linger through tonight
through 18z Monday along with rainfall, with snow above 6500 feet.
Cigs will gradually lift after 18z Monday with lingering areas of
MVFR conditions continuing as the asct low pressure system
responsible for the clouds/precip tracks northeast to Northeast
Wyoming by 00z Tuesday.

&&

.FIRE WEATHER...
Issued AT 230 AM MDT Sun Sep 24 2017

Fuels at critical levels for most of the low elevation forecast
zones east of the Divide and across southern Wyoming. (Please see
the Fire Weather Forecast product for more information).

Today through Monday will be cool/seasonably cold across the
forecast area. Additionally, copious moisture/rainfall/mountain
snowfall will continue east of the Divide today. Significant
precipitation values can be expected in one form or another...with
areas east of the Divide having a chance to get from a quarter
inch to a half inch of liquid. Winds will periodically gust 25 to
35 mph across southern Wyoming today, before becoming light
Monday and Tuesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM MDT this evening for WYZ008-
009-014-015.

&&

$$

SHORT TERM...LaVoie
LONG TERM...AR
AVIATION...Lipson
FIRE WEATHER...LaVoie



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