Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 070549
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1049 PM MST Wed Dec 6 2017

.SHORT TERM...(This evening through Saturday)
Issued at 215 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 215 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 06Z TAFS through 06Z Friday)
Issued at 215 PM MST Wed Dec 6 2017

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

VFR conditions will prevail through the period. A gusty wind will
occur at most sites Thursday with the wind decreasing after 00Z Fri.

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

VFR conditions will prevail through the period. A gusty wind will
occur in northern Johnson county Thursday afternoon and Thursday
night. A gusty wind will develop Thursday afternoon at KRIW airport
with decreasing wind after 02Z Friday.

&&

.FIRE WEATHER...
Issued AT 215 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...NONE.

&&

$$

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



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