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Area forecast discussion 
National Weather Service Riverton Wyoming
236 am MST Monday Mar 2 2015

Short term...today through Wednesday night

Forecast still on track for the upcoming storm system to impact the
area through Tuesday evening. Precipitation will begin across
southern Sweetwater County this morning and afternoon...but
temperatures will be too mild to produce much in the way of
hazardous conditions.

A Canadian cold front and associated snowfall will impact northern
Wyoming this evening with periods of moderate snowfall...strong
wind...and much colder temperatures. This system will quickly move
south through the forecast area through the evening hours. The
system will combine with the already occurring precipitation across
Sweetwater...southeastern Fremont...and Natrona counties to create
winter storm conditions with periods of heavy snowfall and gusty
wind. Winter storm warnings have been issued for these areas for
this evening through Wednesday afternoon.

General belief is that the flow is not quite ideal for the inclusion
of the Lander foothills in the Winter Storm Warning. Their expected
snowfall amounts have left them to be included in the Winter Weather
Advisory...though it is possible some areas in the Lander foothills
may very well see higher amounts of snowfall. Also decided to
include the western slopes of the Wind River mountains in the
advisory to cover the full length of Highway 28 through South Pass
where wind and snowfall will result in hazardous travel conditions
overnight.

Snowfall still looks to taper off quickly Tuesday night with
building northerly flow. Generally dry conditions anticipated by
late Wednesday morning across the forecast area. The colder
temperatures associated with this system will linger through
Wednesday...with single digits expected Wednesday night.

Long term...Thursday through Monday

A relatively dry northwest flow...and a warming trend to seasonal
levels will occur late this week...and remain in place through early
next week. The main caveat is the European model (ecmwf) still shows a distinct
shortwave trough...and associated weak cold front pushing southeast
across the area in the Friday/Saturday time frame. However...the 00z
GFS and Gem are keeping this wave less amplified and farther
northeast. Will have some slight mountain probability of precipitation for this system
Friday and Saturday...but if models trend toward the European model (ecmwf)...probability of precipitation
will need to be expanded and increased...mainly Friday
night/Saturday.

&&

Aviation.../12z issuance/

East of The Divide...kcod/kcpr/klnd/kriw/kwrl routes
VFR conditions...Florida scattered-bkn200-250 across the south half of
Wyoming...will prevail through 18z. A low pressure system lifting NE
across the Great Basin will push scattered MVFR -shrasn north to a vicinity
klnd-kcpr line 21z Monday-00z Tuesday. Conditions will then deteriorate
rapidly after 00z Tuesday as a cold front pushes down from the north
bringing widespread MVFR/IFR -sn and mountain obscurations across the
area by 4z Tuesday. The heaviest snowfall and areas of LIFR conditions
will be found vicinity and south of a kcpr-klnd line. These conditions
will persist through 12z Tuesday.

West of The Divide...kbpi/kjac/kpna/krks routes
an upper level disturbance will bring an initial band of MVFR/IFR
-sn north into southern Wyoming to vicinity and south of Interstate 80
11z-15z Monday. There should be some improvement across the south in
the late morning...and then more widespread persistent IFR snow is
expected to develop across southern Wyoming around 20z Monday and
persist into the overnight hours. A Canadian cold front pushing
down from the north will spread snow south along The Divide Monday
evening...filling western Wyoming with widespread MVFR/IFR -sn by
06z Tuesday along with mountains becoming mostly obscured.

&&

Fire weather...

A wintry storm system is still on track to impact the forecast area
this evening and through Wednesday morning. Much of the area is
anticipated to experience light to moderate snowfall amounts...with
areas of southwestern Wyoming expected to see enhanced snowfall. In
addition to snowfall...the approaching Canadian cold front will
bring much colder temperatures...and periods of very strong wind
through the overnight hours.

&&

Riw watches/warnings/advisories...
Winter Storm Warning from 6 PM this evening to 6 PM MST Tuesday
wyz019-020-022-030.

Winter Weather Advisory from 6 PM this evening to 6 PM MST
Tuesday wyz002>011-014>018-028-029.

&&

$$

Short term...branham
long term...wm
aviation...aem
fire weather...branham

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