Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 210523
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1123 PM MDT Sun May 20 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 231 PM MDT Sun May 20 2018

A Pacific low pressure trough extending south from the Pacific
Northwest into the Great Basin will deepen and continue to move
east spreading moisture and instability across the area producing
scattered showers and isolated thunderstorms with small hail and
gusty winds this evening and again on Monday.  Clouds and
precipitation will become more widespread on Tuesday with areas
of heavy rain along and east of the Continental divide. Temperatures
will warm on Monday with favorable relative humidity.  Then cool
on Tuesday with elevated relative humidity as precipitation becomes
more widespread on Tuesday.  The air mass will be more stable on
Wednesday decreasing precipitation coverage and intensity,
especially across the south.

.LONG TERM...(Wednesday night through Sunday)
Issued at 231 PM MDT Sun May 20 2018

On Wednesday night and Thursday, the trough to our west will
approach the Northern Rockies and ride up and over the long wave
ridge in the Western United States in the form of a weak closed low
arching east across Montana. As this happens expect a good chance of
convection across the west and far north Wednesday night and into
Thursday. Expect scattered thunderstorms in these areas Wednesday
evening and again late Thursday as the 700mb asct cool front tracks
southeast across the area. After the passage of this weather
feature, an amplified ridge will build into the area from the west
with only late day isold convection expected in the mtns Friday
through Sunday. Temps Thursday in the lower elevations will be in
the 70s east of the divide and 60s west. Friday through Sunday highs
will be in the low 80s and 70s respectively. Jackson could even
approach 80 by Saturday. This warming will likely increase mtn
snowmelt, potentially increasing the flow in the main stem rivers.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1123 PM MDT Sun May 20 2018

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

Mainly VFR conditions are expected through the forecast period
through Monday evening. Have introduced a VCTS mention for Monday
afternoon between the 19Z-21Z time frame for KJAC, KBPI and KPNA
sites due to a slightly better chance of more widespread showers
and thunderstorms through Monday evening. Winds are expected to
shift to the northwest across the area between 22Z-02Z time frame
and have kept winds up to around 8-9 knots at most sites.

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

Mainly VFR conditions are expected through 18Z Monday. Isolated
late day thunderstorms are expected Monday afternoon with a better
chance in the mountains and at the KCOD taf site. Winds should
shift to the northwest by between 21Z-02Z at the sites.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.


&&

.FIRE WEATHER...
Issued AT 231 PM MDT Sun May 20 2018

A Pacific low pressure trough extending south from the Pacific
Northwest into the Great Basin will deepen and continue to move
east spreading moisture and instability across the area producing
scattered showers and isolated thunderstorms with small hail and
gusty winds this evening and again on Monday.  Clouds and
precipitation will become more widespread on Tuesday with areas
of heavy rain along and east of the Continental divide. Temperatures
will warm on Monday with favorable relative humidity.  Then cool
on Tuesday with elevated relative humidity as precipitation becomes
more widespread on Tuesday. Mixing heights will be favorable
even with relatively light transport winds to produce good or
better smoke dispersal each afternoon through Tuesday.

&&

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

$$

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


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