Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 131626
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1026 AM MDT Fri Apr 13 2018

.SHORT TERM...Friday through Sunday night

Still a complicated forecast although we are now on the downward
side of the complicated and pain in the neck system. We still have a
few showers out there this morning although at this point nothing
heavy. Precipitation out west looks to be on a downward trend and
may be killed with the morning issuance. The theme for today will be
windy and showery for most locations. With northwest flow, we could
see a few of those pain in the neck snow bands develop although
accumulation is questionable given daytime temperatures above
freezing and the high sun angle, now equivalent to late August. The
models are showing wrap around moisture possibly making back into
portions of Johnson and Natrona Counties at times today with some
snow. Accumulations may not cause to much impact though given the
recent warm temperatures that could prevent accumulation on paved
surfaces, especially during the day. The main story today will the
gusty to strong wind across many areas. At this time, winds look to
be just below high wind criteria for most locations. The exception
may be Johnson County, but with a winter weather advisory in effect
we will cover for strong winds in that. These winds should decrease
later this afternoon as the low moves away and the pressure gradient
decreases. All snow should end by around midnight with dry
conditions after that.

Quiet weather then moves in for the weekend. Areas East of the
Divide should be dry with a mixture of clouds and sunshine along
with light to moderate winds. Temperatures should remain cool on
Saturday before warming on Sunday. A couple of weak shortwaves will
brush by the northern mountains from Saturday afternoon into Sunday.
However, with little moisture we only have slight chance to chance
POPS with any showers of the light variety.

.LONG TERM...Monday through Friday

Ahead of a large scale trough along the West Coast, an unseasonably
warm and windy day is expected ahead of a cold front that should
push into western Wyoming Monday afternoon. Ahead of the cold front
elevated fire weather conditions are expected from Rock Springs to
Casper, as well as parts of the Wind River Basin. The cold front is
expected to rapidly shift east across the forecast area Monday
night. Showers could occur along and behind the cold front. There is
even a chance of a few thunderstorms along the front. Tuesday will
be much cooler with isolated to scattered snow showers continuing
across the area.

Dry and warmer conditions are expected Wednesday as a transitory
ridge pulls across the area. Another upper low/trough pulls into the
West Coast Wednesday night. The northern part of the trough weakens
while the southern energy becomes a closed upper-low over the Desert
Southwest Thursday. This upper low is then progged to shift east
into the Four Corners area by around 12Z Friday, before pulling into
the central High Plains. Some precipitation could develop over
western Wyoming Thursday, before spilling east of the Divide
Thursday night and Friday. Based on its current track, the bulk of
the precipitation would be just southeast of the area, but this
system will need to be watched for central/southern zones for the
possibility of some heavy wet snow wrapping into the area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1017 AM MDT Fri Apr 13 2018

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

Isolated snow showers will continue through this afternoon over
the Wind River mountains and the Absaroka mountains, with mountain
obscurations over the highest peaks. Will put VCSH at KRKS
airport from 00Z to 06Z Saturday. MVFR conditions will occur in
the snow showers. Skies will begin to clear across the area after
00Z Saturday, before BKN-OVC FL120-200 return from the NW after
12Z. Gusty wind will occur at most terminal sites through 02Z
Saturday.

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

Rain and snow showers remain well east of KCPR this morning and
are not expected through the rest of the day today. Any shower
that does develop this afternoon will be due to clearing skies
over central portions. Gusty north-northwest winds are expected to
return this afternoon, before subsiding again this evening. VFR
conditions are expected through the TAF period, with BKN-OVC
FL120-200 clouds returning across the area during the day
Saturday.

&&

.FIRE WEATHER...

Expect much cooler conditions across the area today following the
passage of a cold front. There will be the chance of snow showers
for many areas. especially across Natrona and Johnson Counties.
Gusty to strong winds will be common for many areas, with the
strongest winds in Johnson County and the northern Big Horn basin.
Relative humidity will remain well above critical levels. Mixing and

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Hattings
LONG TERM...Murrell
AVIATION...LaVoie
FIRE WEATHER...Hattings



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