Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 242008
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
208 PM MDT Sun Sep 24 2017

.SHORT TERM...(This evening through wednesday)
Issued at 210 PM MDT Sun Sep 24 2017

A cold upper low pressure low center over Utah and southwest
Wyoming will lift north and east.  This will bring widespread rain
and snow, mainly above 7500 feet to the Wyoming, Salt river,
Wind River and Gros Ventre mountains with areas of 5 to 10 inches
in the Wind River mountains and 4 to 7 inches in the Wyoming,
Salt River, Gros Ventre, Absaroka and Bighorn mountains.  The
lower mountains, Owl Creek, Green, Rattle Snake and Casper
mountains can expect 2 to 4 inches. Lighter amounts are expected
to the north.  Temperatures will be cold with very high relative
humidity.  The snow and rain will taper off through the early
morning with clearing from northwest to southeast.  Some showers
will develop over the mountains with heating by afternoon.
Temperatures will warm slightly Monday, with a cold night Monday
night with clearing.  Areas of fog are expected.  Tuesday
and Wednesday will be warmer with drying.

.LONG TERM...(Wednesday night through Sunday)
Issued at 210 PM MDT Sun Sep 24 2017

High pressure ridge continues to build in from the west Wednesday
night. Thursday morning will feature another hard freeze for the
western valleys for a while before temps continue to warm with the
building ridge. By Thursday, sunny skies with pleasant fall high
temperatures in the 60s in the western valleys and 60s and 70s at
the lower elevations will be seen east of the divide. These warm
temps should persist all the way through next weekend.

On Thursday, the models bring a weak low northeast from the 4
corners area, northeast toward Wyoming. The GFS continues to bring
the asct mstr with it far enough northeast enough to skirt Southern
Sweetwater County by Friday with the Euro keeping it south of there.
Will keep the idea of low pops in the forecast for Southern
Sweetwater County for Thursday and Friday.

The models begin to diverge more significantly by next weekend with
the GFS and the Euro bringing in the next shortwave, flattening the
ridge, through Saturday with the GFS indicating somewhat of a
stronger west northwest difluent flow pattern. The Canadian cuts off
this shortwave and keeps the resultant cut off low over the Great
Basin. Will keep very low pops in NW WY for now to account for this.
Will also keep low pops in NW WY for Sunday night to account for the
wnw diffluent flow behind Saturdays shortwave.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 210 PM 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 210 PM MDT Sun Sep 24 2017

A cold upper low pressure low center over Utah and southwest
Wyoming will lift north and east.  This will bring widespread rain
and snow, mainly above 7500 feet to the Wyoming, Salt river,
Wind River and Gros Ventre mountains with areas of 5 to 10 inches
in the Wind River mountains and 4 to 7 inches in the Wyoming,
Salt River, Gros Ventre, Absaroka and Bighorn mountains.  The
lower mountains, Owl Creek, Green, Rattle Snake and Casper
mountains can expect 2 to 4 inches. Lighter amounts are expected
to the north.  Temperatures will be cold with very high relative
humidity.  The snow and rain will taper off through the early
morning with clearing from northwest to southeast.  Some showers
will develop over the mountains with heating by afternoon.
Temperatures will warm slightly Monday, with a cold night Monday
night with clearing.  Areas of fog are expected.  Tuesday
and Wednesday will be warmer with drying.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MDT tonight for WYZ014-
015.

&&

$$

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


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