Area Forecast Discussion
Issued by NWS Riverton, WY

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062
FXUS65 KRIW 250501
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1100 PM MDT TUE MAY 24 2016

.Short Term...Tonight Through Wednesday

A major long wave low pressure trough extending from the eastern
Pacific off of the west coast to the eastern great plains will
remain over the region. This will keep cool air over the region
with southwest flow bringing Pacific moisture north along with
instability and jet dynamics supporting shower activity with
embedded afternoon and evening thunderstorms. Thunderstorms will
have small hail...heavy rain and strong wind gusts. Gusty
southwest winds will extend across the lower elevations of the
Red Desert...Wind River and Bighorn basins and Fremont...Natrona
and Johnson counties. Night time freezing to near freezing
temperatures in the mountains will retard the snowmelt. The snow
level will continue to fluctuate between 9000 feet and 7500 feet
day to night. Above 9000 feet accumulations of 2 to 4 inches a
day is expected. Some accumulation may occur below 9000 feet down
to around 8000 feet. Showers and thunderstorms will produce daily
precipitation from .25 to .5 of an inch with local 1 inch amounts.

.Long Term...Wednesday Night Through Tuesday

A major long wave low pressure trough extending from the eastern
Pacific off of the west coast to the eastern great plains will
remain over the region Wednesday night trough Tuesday. This will
keep cool air over the region with southwest flow bringing Pacific
moisture north along with instability and jet dynamics supporting
shower activity with embedded afternoon and evening thunderstorms.
Thunderstorms will have small hail...heavy rain and strong wind
gusts. Gusty southwest winds will extend across the lower
elevations of the Red Desert...Wind River and Bighorn basins and
Fremont...Natrona and Johnson counties. Night time freezing to
near freezing temperatures in the mountains will retard the
snowmelt. The snow level will continue to fluctuate between 9000
feet and 7500 feet day to night. Above 9000 feet accumulations of
2 to 4 inches a day is expected through the week. Some
accumulation may occur below 9000 feet down to around 8000 feet.
Showers and thunderstorms will produce daily precipitation from
.25 to .5 of an inch with local 1 inch amounts. The extended
models start to diverge over the weekend and spread apart more
Monday and Tuesday with speed...strength and location of short
wave low pressure troughs.

&&

.AVIATION.../06Z ISSUANCE/

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

VFR conditions to prevail at the terminal sites except across the
far west...excluding KJAC which will see continuing vcnty -SHRA or
prevailing -SHRA and MVFR/occasional IFR conditions from now through
most of the forecast period. As one upper level disturbance moves
quickly and exits northern/northeastern Wyoming this morning,
another disturbance will keep isolated to scattered showers across
west and northwest Wyoming through the morning hours with frequent
mountain obscuration. Early morning low stratus and MVFR ceilings
or VCFG return to some terminals after 09z. Otherwise, showers and
isolated thunder will return to the rest of the region by mid to
late morning...lasting through the rest of the day before finally
decreasing in coverage by Wednesday evening. Brief periods of MVFR
cigs may be experienced with any heavier shower or storm.


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

VFR conditions to prevail through the forecast period. The strong
upper level disturbance that brought showers and thunderstorms to
the region Tuesday, will move out of northern Wyoming this
morning...with showers ending across most of the area.
Showers and isolated thunder will again be possible by mid to late
morning near KCOD, then by early afternoon elsewhere. These showers
and storms may last into the mid evening period before decreasing in
coverage. Brief periods of MVFR cigs may be experienced with any
heavier shower or storm.

&&

.FIRE WEATHER...

A major long wave low pressure trough extending from the eastern
Pacific off of the west coast to the eastern great plains will
remain over the region into the weekend.  This will keep cool air
over the region with southwest flow bringing Pacific moisture north
along with instability and jet dynamics supporting shower activity
with embedded afternoon and evening thunderstorms. Thunderstorms
will have small hail...heavy rain and strong wind gusts. Over
the mountains...relative humidity will be elevated with lower
relative humidity and gusty southwest winds across the lower
elevations of the Red Desert...Wind River and Bighorn basins and
Fremont...Natrona and Johnson counties. Night time freezing to
near freezing temperatures in the mountains will retard the
snowmelt. The snow level will continue to fluctuate between 9000
feet and 7500 feet day to night. Above 9000 feet accumulations of
2 to 4 inches a day is expected through the week. Some
accumulation may occur below 9000 feet down to around 8000 feet.
Showers and thunderstorms will produce daily precipitation from
.25 to .5 of an inch with local 1 inch amounts. Outside of areas
of precipitation...mixing heights should rise high enough for good
to very good smoke dispersal in the afternoons.

&&

.RIW Watches/Warnings/Advisories...
None.
&&

$$

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



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