Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 212311
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
411 PM MST Tue Feb 21 2017

.SHORT TERM...Tonight through Friday

The grand finale of the Western wyoming snowstorm will continue
through tonight with the snow intensity and wind speeds gradually
diminishing tonight. A slice of this precip will be breaking off
this large area of precip and slide southeast across areas east of
the Divide tonight as the associated cool front tracks southeast
across the area. The rain has already turned to snow in the
Jackson valley and is in the process of changing over in the Star
Valley. Will let the winter storm warnings in the west ride
through 12z Thursday. Light snow will continue in the west
Wednesday without much accumulation. Otherwise the weather will be
somewhat benign Wednesday.

Then the well advertised low pressure system threatening to dump
potentially heavy snowfall to Central and Southern Wyoming will
begin to affect the area 06z Wednesday night. The GFS and the Euro
have now come around to depicting a more northern scenario than
the previous runs have indicated and look more like the original
runs. The Euro is the farthest north. For now it appears that the
low will be vertically stacked and track east across South Central
Wyoming with a large swath of isentropic lift streaming north
ahead of it. In addition, ample QG forcing, close proximity to
the circulation, and good dendritic growth could result in
copious amounts of snowfall late Wednesday night through mid day
Friday. Upslope will put the finishing touches on the event. It
appears the bulls eye of the storm in our CWA will be the Casper
area with a potential of 18 inches of snowfall in Casper and up to
two feet on Casper Mountain by Friday. Less snow, but still
significant snow will fall to the west and north with 6 to 10
inches in the Lander Riverton area.

In the meantime, light snow will continue in Western Wyoming
through Friday.


.LONG TERM...Friday night through Tuesday

Very active period as mean trough reloads over the area next week
leading to more significant storm potential east of the divide early
next week. Northwest flow with an embedded shortwave or two behind
our major Wednesday night through Friday storm to keep us unsettled
to start this period. We might get a brief respite on
Sunday...maybe...but then we get right back into the significant
storm potential Monday through Tuesday (and beyond). Fresh snow
cover will give some of the central zones a cold Friday
night/Saturday and possibly Sunday period but active pattern may
limit how cold it can get with clouds, snow showers around and even
some wind potential. Next cold system diving down from the PacNW
into the Great Basin early next week has more significant storm
potential with dynamics from the sw overrunning cold dome/upslope
from the srn Canada surface high. Amazingly busy pattern continues
well beyond this period.


&&

.AVIATION.../00Z ISSUANCE/

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

Snow in the mountains through tonight with IFR/LIFR conditions.
Rain and snow mixed in the western valleys through 00Z, then all
snow by 00Z to 03Z Wed. Expect MVFR to IFR conditions at times at
KPNA and KBPI. KRKS will remain VFR through tonight with gusty
wind at times.

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

VFR conditions will prevail at the terminal sites through most of tonight
but there will be a band of showers passing through with a cold
front that will produce brief lcl mvfr cigs. Gusty to strong wind
will occur through tonight with high winds quite possible around
KLND and KCOD overnight. LLWS will also occur around KCOD through
tonight. Please check the latest terminal forecast for more
details.

&&

.FIRE WEATHER...

Accumulating snow and wind will gradually diminish tonight in the
west. A narrow line of rain turning to snow will spill over to
areas east of the Divide this evening. A significant snowstorm may
impact a large portion of Southern and Central Wyoming east of the
Divide from late Wednesday night through Friday. Colder
temperatures are expected later this week.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Wednesday evening through Friday morning
for WYZ007-011-014-015-017>020-022-030.

High Wind Warning until 11 PM MST this evening for WYZ005-
009>011-018>020.

Winter Storm Warning until 5 AM MST Wednesday for WYZ001-002-012-
014-015-024.

High Wind Warning from 7 PM this evening to 11 AM MST Wednesday
for WYZ003.

&&

$$

SHORT TERM...Lipson
LONG TERM...Skrbac
AVIATION...Skrbac
FIRE WEATHER...Lipson


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