Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 270556
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1156 PM MDT Fri May 26 2017

.SHORT TERM...(This evening through Monday)
Issued at 240 PM MDT Fri May 26 2017

Cold front from Montana has moved south into northern Fremont and
northern Natrona county with clouds and light showers, colder air
and northerly winds moving south behind the cold front. An upper
level low pressure storm center moving over eastern Idaho will
move southeast tonight and Saturday enhancing dynamics and lift
over the front with a significant increase in precipitation with
the potential for heavy snow in the Absaroka and Wind River
mountains and the northern Bighorn mountains above 8800 feet.
Isolated thunderstorms will be possible with local heavier
rainfall/snowfall. The precipitation will continue through tonight
and then taper off Saturday morning as colder air in northerly
flow aloft moves in. In the Southern Absaroka and Winder River
mountains above 9000 feet, snowfall of 5 to 10 inches is
possible. Some clouds and lighter showers will linger over the
area Sunday with the greatest coverage in the mountains. Mountain
showers will linger through Monday. Temperatures will be cold
with little snow melt above 8500 feet.

.LONG TERM...(Monday night through Friday)
Issued at 240 PM MDT Fri May 26 2017

After lingering evening convective activity Monday evening, a large
area of high pressure will build in from the west and our nw flow
will become more confluent along with a loosening gradient.
Temperatures will warm up nicely through the rest of the week with
h7 temps warming to around 10c by Wednesday with highs in the upper
70s to low 80s at the lower elevations east of the divide and low
70s west by then. In fact this area of broad high pressure will be
with us at least through next Friday. The ridge of high pressure
will get pinched off somewhat by Wednesday as a closed low becomes
established over Southern California and the next upstream trough
approaches the Pac NW. Several weak waves will ride up and over this
ridge somewhat resembling the summertime "ring of fire" along with
plenty of instability around and enough moisture for late day
thunderstorms each day. The models appear to agree with one another
on this more so than they did 24 hours ago. With that said, there
will be plenty of instability around and enough moisture for late
day thunderstorms each day.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1155 PM MDT Fri May 26 2017

West of the Continental Divide...KBPI/KJAC/KPNA/KRKS Terminals

Isolated to scattered rain and snow showers, mainly over the
mountains, will continue to dissipate with clouds scattering out
early this morning.  This will allow patchy fog to develop vicinity
KJAC until around 14z.  The exception to the clearing trend will be
KRKS where some lower MVFR ceilings may back into the area from the
north through around 13z. VFR conditions will then prevail from 14z
Saturday onward.  Slight instability will result in isolated showers
and thunderstorms developing in the vicinity of the Continental
Divide with this convection tracking off the southern end of the
Wind River Range but should dissipate before reaching vicinity KRKS.
This activity will dissipate with sunset, leaving prevailing SKC-FEW
FL130-150.


East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

An upper trough will continue to push southeast across the area
overnight with isolated to scattered showers mainly vicinity KRIW-
KCPR.  This activity should be mostly south and east of the area by
12z, with some clearing and patchy fog partially obscuring terrain.
Slight instability Saturday afternoon will result in isolated
showers and thunderstorms developing along mountain valley/breeze
boundaries along the south and eastern slopes of mountain ranges and
moving SSE.  This activity mostly anchored to the high terrain and
not impact any terminals.  KRIW-KCPR routes will be most vulnerable
to a few thunderstorms in the vicinity of the southern Bighorn
Range.  Convection will dissipate with sunset, leaving SKC-FEW FL130-
150.

&&

.FIRE WEATHER...
Issued AT 240 PM MDT Fri May 26 2017

Cold front from Montana has moved south into northern Fremont and
northern Natrona county with clouds and light showers, colder air
and northerly winds moving south behind the cold front. An upper
level low pressure storm center moving over eastern Idaho will
move southeast tonight and Saturday enhancing dynamics and lift
over the front with a significant increase in precipitation with
the potential for heavy snow in the Absaroka and Wind River
mountains and the northern Bighorn mountains above 8800 feet.
Isolated thunderstorms will be possible with local heavier
rainfall/snowfall. The precipitation will continue through tonight
and then taper off Saturday morning as colder air in northerly
flow aloft moves in. In the Southern Absaroka and Winder River
mountains above 9000 feet, snowfall of 5 to 10 inches is
possible. Some clouds and lighter showers will linger over the
area Sunday with the greatest coverage in the mountains. Mountain
showers will linger through Monday. Temperatures will be cold
with little snow melt above 8500 feet. With cold air, low clouds and
precipitation mixing heights will be low with generally poor
smoke dispersal through Sunday. Some windier areas may get enough
smoke transport for fair afternoon dispersal, especially on
Sunday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Saturday for WYZ008-009.

&&

$$

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



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