Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 252022
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
222 PM MDT WED MAY 25 2016

.Short Term...Tonight Through Thursday

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 and east 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 continue 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...Thursday Night 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 Wednesday night trough Tuesday. This will
keep cool air over the region with southwest flow bringing Pacific
moisture north and east 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 continue to 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.../00Z Issuance/

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

Another upper level disturbance has been producing scattered to
numerous showers and thunderstorms that will continue to move east
and out of the area through the late afternoon hours before another
band of scattered showers and thunderstorms over eastern Idaho move
back into western Wyoming through early this evening. The showers
will finally decrease in coverage then clear out later this
evening. Brief periods of MVFR/IFR ceilings and mountain
obscurations may be experienced with any heavier shower or storm.
Yet, another upper level disturbance will be swinging through the
area Thursday resulting in another round of numerous showers and
thunderstorms, with the greatest coverage of shower activity in
the afternoon resulting in local mvfr/ifr ceilings along with
mountain obscurations. Some small hail is likely with any storms
that develop through Thursday.


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

A band of scattered showers and thunderstorms extending from the
northern Big Horn Basin...down through the Wind River Basin and on
into South Pass will be moving east during the remainder of the
afternoon. These storms should reach the Casper area by around 5
pm or so. Additional showers and an isolated thunderstorms are
expected for the rest of the evening. These showers will be
decreasing in coverage along with skies clearing later this
evening. Brief periods of MVFR/IFR and mountain obscurations will
be experienced with any heavier shower or storms. A repeat of
mostly scattered afternoon and evening thunderstorms can be
expected by Thursday afternoon as yet another upper level
shortwave comes through. Some small hail is likely with any storms
that develop through Thursday.

&&

.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
and east 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 continue to 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...Lipson
FIRE WEATHER...C.Baker


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