Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 131650

Area Forecast Discussion
National Weather Service Riverton WY
950 AM MST Fri Jan 13 2017

.SHORT TERM...Friday through Sunday night

Mainly settled conditions will dominate through the weekend. The
weak system bringing snow to southern portions of the area last
evening will move away by morning. Following that dry northwest flow
will dominate through the weekend. The result will be dry conditions
and light to moderate winds. The NAM does show a few light showers
across the south. However, since the NAM has been terrible the past
few days and the GFS being dry we only went with some cloud cover
at times. If anything does fall from the sky, it would likely be
nothing more than a few flurries. Otherwise, expect a partly to
mostly sunny sky. Temperatures will be chilly but nothing unusual
for the middle of January. The coldest areas will be the basins
where inversions will setup, as well as the far west with the
deep, fresh snowpack.


Synopsis...Northerly flow aloft will bring cool and dry conditions
across the area on Monday.  A strengthening westerly flow ahead of
the next series of Pacific storm system will bring snowfall of
increasing coverage and intensity into the west Tuesday night
through Wednesday, while windy and milder conditions prevail east
of the Continental Divide. A large upper trough will dig across
the western U.S. Thursday and Friday with the heaviest
precipitation expected to gradually shift south of the area by

Discussion...Strong jet stream nosing its way eastward across the
Dateline in the central Pacific this morning is forecast to reach
the West Coast on Tuesday along 40N and then dig southward across
the SW U.S. Thursday and Friday.   ECMWF and GFS continue to show
poor continuity in the details of large upper trough and individual
shortwaves within the flow, so there is little confidence in the
specifics.  The big picture for the forecast is that westerly flow
and incoming fetch of Pacific moisture should be at a maximum across
western Wyoming on Wednesday/Wednesday night as nose of jet plows
into northern California.  This looks to be the window for possible
Winter Storm highlights in the west, and high wind potential mainly
across southern Fremont and Natrona counties.  Jet buckles and digs
into the southwest U.S. on Thursday with upper flow over Wyoming
decreasing and becoming more southerly, heavier precipitation
shifting into Utah, Colorado. Main upper trough axis is expected to
translate the Rockies Thursday night and Friday with chances of snow
showers spreading into central and eastern Wyoming, but amounts
should be generally light with the heavier snowfall over the
southern/central Rockies.



VFR conditions and generally clear skies will prevail through the
forecast period for most terminal locations. KRKS, however, will
continue periods of varying VFR to IFR CIGs through the forecast
period as an exiting upper level disturbance keeps clouds, a few
flurries and vcnty FG around the area through 18z Saturday.
Additionally, patchy fog may redevelop in the mountain valleys and
basins of central, southern and western WY later this evening...with
the potential to last through 18z Saturday locally. Winds will
remain light for all areas through the forecast period.



Fire Danger low for all of WY through, at least, the weekend. Cold
seasonal temperatures, good existing snow pack, and relatively light
winds will characterize the next several days. Smoke dispersion will
also remain poor for all locations through the weekend.




SHORT TERM...Hattings
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