Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 262105
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
205 PM MST Sun Feb 26 2017

.Short Term...Tonight Through Wednesday

Sufficient low and mid level moisture in west flow aloft to
support continued light snowfall over western mountains Tonight.
Flow aloft slowly shifts to the west southwest with increasing
moisture through Monday.  Variable clouds will spread east of
the mountains with little precipitation spilling over the
Continental Divide. Some light snow is possible near the
foothills. Otherwise rather brisk and gusty winds will continue
over and near the east slopes of the mountains and through the
wind corridor from Rock Springs to Casper.  Windy areas will
see some warming while the valleys and basins with light wind
will see little change in temperatures. In the west Snowfall of 3
to 6 inches every 24 hours with local 8 inch amounts in the
Tetons and Southwest Yellowstone National Park continues through
Wednesday. Temperatures will be rather steady through Mid Week.
Brisk winds at ridgetop and pass levels will continue with a
gradual increase Tuesday.

.Long Term...Wednesday Night Through Sunday

Wednesday night through Thursday night: Post frontal with general
high pressure at the SFC, cool NW flow aloft, and some lee troffing
trying to get started east of the Continental Divide. Modest
moisture will also continue to flow into the region from the PAC NW.
This set-up will keep the northwest/northern portion of the FA
slightly unstable, and with a little extra mountain lift, will keep
the mountains across northern WY under conditional POPs.
Temperatures at all locations through Thursday will also remain
largely below seasonal so snow melt should remain in check.

Friday through Sunday: Weak ridging/upper level NW flow will begin
to flatten in response to an approaching embedded upper level SW
trof/jet streak that will arrive near western WY Friday night. The
transition to nearly zonal flow on Friday will allow for increased
lee troffing potential...and the wind potential that comes with it.
Some strong gusty winds, bordering on `High,` will be in-store
periodically for the usual suspect areas (lee side foothills east of
the Divide and across the Wind Corridor) from Friday through much of
the day Sunday. Additionally, relatively light snowfall will
continue in some fashion over northwestern WY until Saturday morning
and the arrival of the nose of the jet when precipitation will
increase spatially and in intensity across the western mountains. If
position and timing of this system remain on track, highlights will
surely be needed over the last couple days of the forecast period.
Otherwise, temperatures will respond positively to the lee side
troffing/wind set-up east of the Divide from Friday through Sunday.
High temperatures will rise back to near seasonal norms, starting
another period of melt-off...but hopefully not to an extreme.

&&

.Aviation.../00Z Issuance/

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

VFR to occasional MVFR conditions will prevail until later this
evening for all terminal sites, except KJAC which will be (or near)
MVFR already, as an upper level disturbance moves into/across WY.
Clouds and snow showers will continue to increase in coverage and
intensity across the western mountains, vicinity and north of a KEMM-
KBPI line, with MVFR/IFR conditions prevailing near KJAC after 03Z
and the rest of the western terminals sometime after
06Z...persisting most of the time through the end of the forecast
period.

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

VFR conditions will prevail through the forecast period for most
locations except KCOD which may see brief periods of MVFR conditions
in lower CIGS and possible reduced VIS Monday afternoon. Otherwise,
southwest winds will continue to gust across a few central WY
foothill locations in addition to the wind corridor, vicinity 50SM
NE KRKS-KCPR, gusting 15 to 30 knots at times. These gusty southwest
winds will decrease by mid-day Monday.

&&

.Fire Weather...

Sufficient low and mid level moisture in west flow aloft to
support continued light snowfall over western mountains Tonight.
Flow aloft slowly shifts to the west southwest with increasing
moisture through Monday.  Variable clouds will spread east of
the mountains with little precipitation spilling over the
Continental Divide. Some light snow is possible near the
foothills. Otherwise rather brisk and gusty winds will continue
over and near the east slopes of the mountains and through the
wind corridor from Rock Springs to Casper.  Windy areas will
see some warming while the valleys and basins with light wind
will see little change in temperatures. In the west Snowfall of 3
to 6 inches every 24 hours with local 8 inch amounts in the
Tetons and Southwest Yellowstone National Park continues through
Wednesday. Temperatures will be rather steady through Mid Week.
Brisk winds at ridgetop and pass levels will continue with a
gradual increase Tuesday.  Poor smoke dispersal is expected through
Wednesday in the valleys. The windy areas over and near the
mountains and through the wind corridor may experience fair to
good smoke dispersal in the afternoons through Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...C.Baker
LONG TERM...Braun
AVIATION...Braun
FIRE WEATHER...C.Baker



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