Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 312102

Area Forecast Discussion
National Weather Service Riverton WY
302 PM MDT Tue Mar 31 2020

.SHORT TERM...This evening through Wednesday night
Issued at 250 PM MDT Tue Mar 31 2020

West of the Divide...

Snow showers will continue in the western mountain and valleys late
into tonight as the shortwave continues through the longwave trough.
We will continue the winter highlights into the evening. Snowfall
rates will drop off rapidly around midnight so the end time for said
highlights still look good. Light snow showers will continue through
the day Wednesday, but most of the activity will be in the
mountains. Better upper level forcing will move into the north
Wednesday night along with the main energy of the longwave trough.
This will start a short period of moderate snow in the Yellowstone
NP. At this time, new highlights do not look necessary.

East of the Divide and Sweetwater County...

Strong to high winds will continue from Sweetwater to Natrona
counties this afternoon. Winds should slow after 9 pm across the
area, but will remain gusty through midnight. Wednesday looks like a
cooler and breezy day for many areas. Precipitation chances will
increase Wednesday afternoon starting in the north as the trough
approaches from the northwest. Chances will increase through the day
and into the evening. Precipitation will start as rain before
changing over to snow in the evening. The milder weather and warmer
road temperatures will cause the snow to have a hard time
accumulating. However, this will change as much colder air moves in
Wednesday night. Natrona and Johnson counties still look like the
target for the heaviest snow with the front impacting the area as
the right rear quad of the jet streak moving overhead. Snow totals
look to be in the advisory range but will hold off on any highlights
until the current set expire tonight.

.LONG TERM...Thursday through Tuesday
Issued at 250 PM MDT Tue Mar 31 2020

Overview...A broad, longwave trough will be in place over western
Canada and the Northern Rockies/PACNW through Friday night. The
trough will begin to fill by Saturday, with another trough
developing off the West Coast Sunday. Temperatures will be 15 to 30
degrees below normal Thursday and Friday. Precipitation will return
across the far west Monday and Tuesday, as this second trough begins
to split as it moves over the region.

Synopsis...Snow will be ongoing Thursday morning east of the Divide
and southern portions. The heaviest snow will remain over Natrona
County and eastern portions of Sweetwater County. The challenge will
be snowfall totals outside of these two areas. Snowfall rates look
to be light enough that amounts will be minimal, due to the April
sun angle. Despite temperatures forecasted to remain below freezing
during the day, snow could remain heavy enough in Natrona/eastern
Sweetwater counties to remain an impact through the afternoon.

Snow will be winding down Thursday evening, gradually ending through
the overnight hours across the area. Conditions will remain cold
and mainly cold Friday. Isolated snow showers will be possible
over northwest portions. Expect similar conditions for Saturday.

A weak shortwave could impact the forecast area Saturday night into
Sunday, bringing another wave of overnight snow/afternoon rain
showers. Temperatures will rebound back to normal Sunday and Monday,
as southwest winds aloft return. This will be in response to the
aforementioned second trough digging over the WCONUS. Precipitation
will return across the far west Monday afternoon, as this trough
approaches the region. Due to the splitting nature of this trough,
any snow looks to be confined to the mountains during the day. Light
snow accumulations will occur in the lower elevations Monday


.AVIATION...For the 00Z TAFS through 00Z Thursday
Issued at 250 PM MDT Tue Mar 31 2020

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

Brief MVFR conditions will remain possible at KCOD through 02Z this
evening, as showers gradually end over the area. Additional showers
could develop after 18Z Wednesday, with similar conditions. Isolated
shower (valley rain/mountain snow) activity remains possible at KLND
through about 04Z this evening. Winds will decrease in most
locations this evening, with gusts ending across the area between
08Z and 13Z Wednesday. A cold front is expected to pull southward
across northern Wyoming between 06Z and 12Z Wednesday. In wake of
the cold front, expect breezy northerly winds. Clouds will increase
across the area through the afternoon, with VFR/marginal MVFR

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

MVFR/occasional IFR conditions from low visibility/ceilings in snow
are expected through 03Z across Jackson Hole and Star Valley. After
03Z, MVFR conditions to even low VFR conditions are expected.
Western mountains will be obscured through the TAF period. For KRKS,
dry with VFR conditions this afternoon. Winds at RKS will increase
considerably during the day, with gusts reaching 40kts during the
afternoon. VCSH will be possible tonight by 05Z through 12Z
Wednesday morning, as winds continue to decrease.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.


Issued AT 250 PM MDT Tue Mar 31 2020

Snow will continue across western Wyoming this afternoon and
evening, mixed with rain at times in the lower elevations. Areas
East of the Divide will continue to see spotty showers until
sundown. A stray thunderstorm can`t be ruled out. Many areas will
see breezy to windy conditions, with strong to high winds possible
from Eastern Sweetwater into Natrona County through 9 PM. Overnight
recoveries will be great and relative humidity should remain above
critical levels Wednesday. Snow showers will continue in the west
tomorrow, but will be more widely scattered. A stronger cold front
will push through east of the Divide late wednesday afternoon with
much colder temps and widespread snow into Thursday morning. Zones
281, 280, and 300 will see the heaviest snowfall and moderately gusty
winds. Mixing and smoke dispersal will be poor overnight, then good
to very good Wednesday afternoon.


Winter Weather Advisory until 11 PM MDT this evening for WYZ001-

High Wind Warning until 9 PM MDT this evening for WYZ019-020-030.

Winter Storm Warning until 11 PM MDT this evening for WYZ012.



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