Area Forecast Discussion
Issued by NWS Riverton, WY

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429
FXUS65 KRIW 270151
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
755 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 00Z TAFS through 00Z Saturday evening)
Issued at 240 PM MDT Fri May 26 2017

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

An upper level low pressure system now over the Idaho/Wyoming state
will drift east across western Wyoming during the rest of this
afternoon. The line of showers and thunderstorms that were tracking
east across Sweetwater County earlier this afternoon have drifted
off to the east of the area along with the associated cold front.
Areas of rain and mountain snowfall above 8000 feet will continue
mainly north of a KEVW-KPNA line with mountains becoming mostly
obscured with snow above 8000 feet, with widespread MVFR conditions
across the valleys. The atmosphere will destabilize during the
remainder of this afternoon with some lifting of ceilings, isolated
thunderstorms developing with erratic wind gusts and small hail.
Brief IFR/LIFR conditions will be possible if a thunderstorm hits
one of the terminals.  Drier air will push into western Wyoming this
evening with lingering rain and snow showers mainly across the
northwest mountains or vicinity and north of a KJAC-KDUB line after
02z. Partial clearing after 06z Saturday will result in some patchy
fog partially obscuring terrain vicinity KJAC through 15z Saturday.
Expect another round of scattered thunderstorms after 18z Sunday
along with LCL MVFR conditions.

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

An upper level low pressure system will drift east across western
Wyoming during the remainder of this afternoon and across north
central Wyoming this evening. Rain and mountain snow with snow
levels around 7000 feet will be widespread through 00z. MVFR
conditions will be widespread across the area through most of the
rest of this afternoon. The northern portion of the line of showers
and thunderstorms that marched across Sweetwater County earlier this
afternoon will clip Southeast Natrona County including KCPR through
around 22z. Most precipitation will shift into the High Plains this
evening, with gradual improvement from northwest to southeast
overnight into Saturday morning. Expect another round of scattered
thunderstorms after 18z Sunday along with LCL MVFR conditions.


&&

.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...Lipson
FIRE WEATHER...Baker



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