Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 190516
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1116 PM MDT Mon Sep 18 2017

.SHORT TERM...(This evening through Thursday)
Issued at 300 PM MDT Mon Sep 18 2017

A cold wet pacific low pressure trough will bring snowfall
to the western and northern mountains of wyoming this evening.
The heavier snowfall is expected above 8500 feet where 5 to
10 inches of snow can be expected through 9 pm mdt Tuesday
evening. Strong gusty west winds are also expected on the
passes and higher ridges.  Snowfall from 8500 to 7500 feet
is expected to be from 3 to 5 inches.  The lower elevations will
see rain with local heavy rainfall possible.  West to southwest
winds of 30 mph with gusts to 45 mph will be possible Tuesday
in the foothills of the Absaroka and Wind River mountains in the
afternoon.  Precipitation will decrease with partial clearing
Tuesday night and Wednesday with another cold Pacific trough
bringing more snow to the west with cold rain in the lower
elevations Wednesday night and Thursday.

.LONG TERM...Thursday night through Monday night
Issued at 300 PM MDT Mon Sep 18 2017

Synopsis...The forecast remains on track today, as the longwave
trough remains positively-tilted until Sunday. By then, the upper
low begins to fill and shift eastward. The supporting upper-level
dynamics will remain in place through at least Saturday, as a
reinforcing shortwave enters the area. There also could be enough
lift around the upper low on Sunday to keep light precip going
through Sunday night.

Discussion...Not much change from last night`s discussion. The
timing of Thursday`s cold front continues to slow down from
Sunday`s 12Z run. 00Z Friday placement of the front looks to be
through northern Natrona Co. into central Fremont/Sweetwater
counties. By 12Z Friday, there looks to be little movement, being
draped over KCPR, SE Fremont and E Sweetwater counties.
Precipitation will stay confined over northern and western
portions to start the period, gradually shifting eastward Thursday
night into Friday. The strong baroclinic zone associated with the
cold front, placement of the jet and timing of the shortwave will
aid in the precipitation becoming widespread during this time. By
Saturday and Sunday, the areas of precipitation will depend on
the additional shortwaves that round the base of the trough, as
well as the main low itself.

Significant widespread precipitation will be in store through the
period, along with significant mountain snow continuing. Snow
levels should stay above 6500 feet, especially over NW portions.

&&

.AVIATION...For the 06Z TAFS through 06Z Wednesday
Issued at 1110 PM MDT Mon Sep 18 2017

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

VFR conditions will prevail through Tuesday night. A cold front will
move from west to east across the region Tuesday morning with the
front through the region around 18Z. Scattered rain showers will
occur this Tuesday morning and afternoon as the front moves through
the area. Showers will linger over the north through 03Z Wed.
Mountains will be obscured at times. A gusty wind will be common
through Tuesday with the wind gradually decreasing after 01Z Wed.

Please see the Aviation Weather Center for the latest information on
icing and turbulence forecasts.

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

Rain and snow will occur in the west with precipitation decreasing
toward 00Z Wed. Lingering rain and snow showers will occur in NW WY
through 06Z Wed. Mountains will be obscured frequently through
Tuesday evening. Windy conditions will be common at most terminal
sites with the wind gradually decreasing after 01Z Wed. Areas of
MVFR and IFR will occur through 00Z Wed with improving conditions
after 00Z Wed.

Please see the Aviation Weather Center for the latest information on
icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 300 PM MDT Mon Sep 18 2017

A cold wet pacific low pressure trough will bring snowfall
to the western and northern mountains of wyoming this evening.
The heavier snowfall is expected above 8500 feet where 5 to
10 inches of snow can be expected through 9 pm mdt Tuesday
evening. Strong gusty west winds are also expected on the
passes and higher ridges.  Snowfall from 8500 to 7500 feet
is expected to be from 3 to 5 inches.  The lower elevations will
see rain with local heavy rainfall possible.  West to southwest
winds of 30 mph with gusts to 45 mph will be possible Tuesday
in the foothills of the Absaroka and Wind River mountains
and across southern Fremont and Natrona counties in the
afternoon.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 9 PM this evening to 9 PM MDT
Tuesday for WYZ001-002-012-014-015.

&&

$$

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



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