Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 182021
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
121 PM MST Sat Nov 18 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 1254 PM MST Sat Nov 18 2017

Strong winds aloft behind a Pacific low pressure trough will
continue to surface along the Cody foothills bringing periods of
high winds around Clark.  The threat of high winds will continue
into early Sunday morning.  Dry high pressure will be over western and
central Wyoming tonight through Sunday night.  Clouds will increase
on Sunday night with warming temperatures and increasing southwest
winds. The leading edge of Pacific moisture ahead of another
Pacific low pressure trough will begin to produce snow over the
western mountains Monday morning with periods of snow and strong
wind from Monday through Tuesday. Snowfall rates are expected to
fluctuate significantly through  the period. Overall, significant
snowfall may occur with this next event. Temperatures in the
western valleys will be mild with daytime rain to rain snow mixed
changing to snow at night limiting snow accumulations in the valleys.
Little if any precipitation is expected in the lower elevations
east of the Continental divide where strong downslope winds will
warm temperatures.

.LONG TERM...Tuesday night through Saturday
Issued at 1254 PM MST Sat Nov 18 2017

High pressure still dominating Southwest US Tuesday night with an
area of ridging running north into Southern ID. A shortwave looks to
come over the ridge Tuesday night into Wednesday. Mild temps
associated with the ridging will cause this shortwave to bring a mix
of rain and snow to the western portions of our area.  This activity
should clear out Wednesday night as the ridge shifts slightly east.
The ridge will remain over WY through Thursday, making for a dry and
warm Thanksgiving.  12Z runs are in more of an agreement about
Friday with the ridge flattening out to allow the next system
through WY. Timing is still a bit off with the GFS and ECMWF
impacting western areas by Friday morning and the Canadian later in
the day. Something to keep an eye on Friday night, the GFS indicates
a 160kt jet streak pushing into Northern WY in support of the front.
This could give a strong amount of exhaust and potentially make
showers stronger than expected. Saturday should see improving
weather as the ridge reestablishes itself to our west.

&&

.AVIATION...For the 00Z TAFS Sunday through 00Z Monday
Issued at 1254 PM MST Sat Nov 18 2017

Expect VFR conditions to continue through the forecast period. Gusty
wind are still occurring at some locations today. Most will
decrease after 01Z Sunday with the exception of KCOD/KCPR which
will remain gusty through the TAF period. With winds remaining
high in the Cody Foothills and a sfc inversion setting up over
KCOD there is a chance for some wind sheer Sunday morning. See
TAFs for further details.

&&

.FIRE WEATHER...
Issued AT 1254 PM MST Sat Nov 18 2017

Strong winds aloft behind a Pacific low pressure trough will
continue to surface along the Cody foothills bringing periods of
high winds around Clark.  The threat of high winds will continue
into early Sunday morning.  Dry high pressure will be over western and
central Wyoming tonight through Sunday night.  Clouds will increase
on Sunday night with warming temperatures and increasing southwest
winds. The leading edge of Pacific moisture ahead of another
Pacific low pressure trough will begin to produce snow over the
western mountains Monday morning with periods of snow and strong
wind from Monday through Tuesday. Snowfall rates are expected to
fluctuate significantly through  the period. Overall, significant
snowfall may occur with this next event. Temperatures in the
western valleys will be mild with daytime rain to rain snow mixed
changing to snow at night limiting snow accumulations in the valleys.
Little if any precipitation is expected in the lower elevations
east of the Continental divide where strong downslope winds will
warm temperatures.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 5 AM MST Sunday for WYZ003.

&&

$$

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



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