Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 062001
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
101 PM MST Wed Dec 6 2017

.SHORT TERM...(This evening through Saturday)
Issued at 102 PM MST Wed Dec 6 2017

A very large high pressure ridge along the west coast extending
north well above the Arctic Circle will produce some mid clouds
over the north and eat through Friday with some light mountain
snow over the Bighorn and northern Absaroka mountains, otherwise
cool dry northerly flow will dominate over western and central
Wyoming through Saturday. Periods of strong winds will be over
northern Johnson county this evening and again on Friday.  As
the ridge moves slowly east wind aloft will decrease with gradual
warming.  Some valley fog will become a threat late at night
and early in the morning along the rivers of western and central
Wyoming.

.LONG TERM...(Saturday night through Wednesday)
Issued at 102 PM MST Wed Dec 6 2017

On Saturday night, the flattening ridge will reach its highest
amplitude before the approach of the next clipper type system
arrives. This weather feature, much like the one our northeast zones
are currently experiencing attm, will likely come through on Monday.
The GFS has the most amplified version of this feature coming
through Monday, with the Canadian the least aggressive, pulling in
the area of high pressure over the far Western United States into
the west half of Wyoming, along with the Euro somewhere in the
middle. As the previous shift alluded to, will go with persistence
and pick the GFS soln as the next area of low pressure establishes
itself over Hudson bay and pinwheels this next shortwave on through.
So, with that said, expect a fairly mild and quiet day Sunday,
followed by a period of light snow in our eastern zones from limited
moisture originating from the Canadian Prairie, along with brisk nnw
winds and colder temps. As with most clippers, Johnson County will
see the most exaggerated cool down from Sunday through Monday with a
drop in high temps of at least 12 degrees. Then Tuesday and
Wednesday look to be a bit a bit milder along with no precip as the
high to our west builds back in from the west. The far west will not
see much fluctuation in temps to speak of, however. Temperature
inversions will likely be the most persistent in the far west
valleys and basins during the period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday)
Issued at 102 PM MST Wed Dec 6 2017

West of the Continental Divide...KJAC, KPNA, KBPI, and KRKS

VFR conditions with little cloud cover is expected for the rest of
this afternoon. Variable to considerable mid-high level cloudiness
is then expected tonight. Breezy northwest to north winds will
impact the Upper Green River Basin through 7 pm this evening. Winds
at KJAC should remain northerly all day, and could be breezy at
times.

East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL

The worst conditions today are expected over the Bighorn Mountains
and northern Johnson County, where strong northwest wind, low
ceilings, light snow along with some blowing snow will occur. KBYG
terminal could see a prolonged period of MVFR ceilings with flurries
at times with strong northwest wind through Thursday morning.

The KCPR terminal will see MVFR ceilings with even an outside chance
of a snow shower for the rest of this afternoon into early evening.
However, kept ceilings in the low VFR range for now.

Elsewhere, considerable mid-level cloudiness with breezy to windy
north to northwest wind are expected for the rest of this afternoon.
Improving conditions are expected tonight, as any light snow/low
ceilings shifts away from the area.

&&

.FIRE WEATHER...
Issued AT 102 PM MST Wed Dec 6 2017

A very large high pressure ridge along the west coast extending
north well above the Arctic Circle will produce some mid clouds
over the north and eat through Friday with some light mountain
snow over the Bighorn and northern Absaroka mountains, otherwise
cool dry northerly flow will dominate over western and central
Wyoming through Saturday. Periods of strong winds will be over
northern Johnson county this evening and again on Friday.  As
the ridge moves slowly east wind aloft will decrease with gradual
warming.   Some valley fog will become a threat late at night
and early in the morning along the rivers of western and central
Wyoming.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 3 PM MST this afternoon for WYZ010.

&&

$$

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



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