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fxus66 kotx 171217 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
417 am PST Wed Jan 17 2018

Synopsis...
more winter weather will move into the area today with a wintery
mix in the valleys and mountain snow moving across the inland
northwest through Thursday. Anticipate a rain/snow mix in the
valleys and even some light freezing rain along with significant
snow in the Cascade mountains through Wednesday night into
Thursday morning. Valley rain and mountain snow moves east
Thursday. A cooler and showery conditions expected Friday into
Saturday, followed by the potential for more snow and rain by
Sunday.

&&

Discussion...
today and tonight: another storm system will continue to make its
way across the inland northwest. This one has a more well defined
warm front followed by a cold front signature. The warm sector
precipitation will first impact the Cascades early this morning
with a light wintery mix of precipitation. Temperatures along the
east slopes of the Cascades will be near freezing and it's
possible for some light freezing rain/sleet and snow mix. The
Winter Weather Advisory is meant to address this as well as the
next surge of moisture with the cold front later in the afternoon
and evening. The front slowly moves across the region and for
points east of the Cascades expect mainly a valley rain and
mountain snow situation with the cold front finally into and through
the Spokane region Thursday morning.

For other areas today there will be areas of morning fog
restricting visibility for the morning commute and possible
producing slick roads as well. Gusty winds to 25 mph from the
southeast will also be possible in southeast Washington but these winds
will keep the fog and precipitation at Bay the longest with it
remaining mainly dry in this region until early Thursday morning
in the southeast. Tc



Thursday: a moist frontal band will track eastward through the
region Thursday bringing light to moderate precipitation to the
Idaho Panhandle and eastern reaches of Washington and decreasing
precipitation in the Lee of the Cascades. Snow levels will lower
closer to 3000 feet by midday then 2000 feet late afternoon into
the evening as 850mb temperatures cool from around +3c in the
morning toward -1c in the evening. Prior to the switch to snow,
rainfall amounts of half an inch to three quarters of an inch will
be possible across the Idaho Panhandle and eastern third of
Washington with local amounts near an inch possible in the Blue
Mountains, Camas Prairie, Palouse, and southern Shoshone County.
This will create the potential for minor hydrologic issues such as
sharp rises on area streams, ponding water, and potential for mud
and rock slides within steep terrain.

Thursday night through tuesday: unsettled weather is expected to
continue across the northwestern US into early next. The air mass
will cool Thursday night and Friday with the passage of a North
Pacific trough then look for the jet stream to waver back and
forth along the or/Washington border with the passage of multiple storm
systems. Confidence is moderate to high that precipitation will
remain all snow in the mountains. This will also be the case for
the northern mountain valleys with some variations in accumulation
potential possible with time of day. The Columbia Basin including
the Palouse and Spokane area will experience the greatest
fluctuations with the passage of each moisture fetch, some warm
enough to switch to rain and others in the form of cold rain and
snow. The pattern is rather chaotic in the medium range models and
expect to see forecast changes with each run.

We will see a transition to snow for the Blue Mountains, Camas Prairie,
into the central Panhandle mountains Thursday night. Snow shower
activity will increase Friday across the majority of ern Washington and north
Idaho and will linger into Saturday. Several inches of snow will be
possible. Snow will also continue along the Cascade crest and
adjacent upper valleys and those with travel plans should be
prepared for snowy travel across both Stevens and lookout passes
until this system clears out Saturday afternoon/evening. The next
moist laden system arrives Sunday morning bringing the next round
of moderate snows across the northern mountains and mix in the
basin. Snow showers linger for Idaho and Cascade passes into
Monday while much of the region dries out but the potential for
another moderate precipitation event arrives Tuesday. Overall, the
mountains will the potential to pick up a few feet of snow over
the course of the week while some valley locations of north Idaho
and NE Washington could see six or more inches. Keep in mind, this will
come in several waves and spread out over the course of 4-6 days
so although travel impacts are likely, we are not looking at any
major winter storms at this time, just a return to winter weather.
/Sb

&&

Aviation...
06z tafs: conditions will be highly variable for many taf sites as
a weather front closes in on the region. Low level moisture in
the form of fog with lower ceilings/visibility will impact several taf sites
expect periodic MVFR/IFR conditions from eat/mwh/geg/sff/Coe
through much of the morning, but the incoming front and
precipitation threat may allow this to mix up a bit adding to the
uncertainty and variability. -Sn will be possible around eat in
the morning hours, transitioning to a -ra in the afternoon.
General improvement toward MVFR/VFR conditions is suggested toward
middle to late Wednesday morning. Stronger southeast winds from
kpuw southward can be expected into Wednesday evening keeping kpuw
and klws taf sites VFR. A cold front starts to approach from the
west 12z Thursday increasing the threat of precipitation. Carter

&&

Preliminary point temps/pops...
Spokane 39 37 42 30 37 30 / 0 80 90 40 20 30
Coeur D'Alene 40 38 40 30 36 30 / 10 80 90 50 30 50
Pullman 47 39 46 32 39 31 / 0 60 90 30 20 50
Lewiston 50 41 48 34 43 33 / 0 30 100 30 20 20
Colville 37 35 40 30 36 29 / 20 90 70 40 20 30
Sandpoint 39 34 40 31 35 30 / 20 90 90 60 40 60
Kellogg 40 34 39 29 34 29 / 0 70 100 50 30 60
Moses Lake 41 36 46 30 41 30 / 10 70 30 10 10 10
Wenatchee 37 31 39 28 37 29 / 50 100 30 10 10 10
Omak 36 32 36 27 34 27 / 60 100 40 10 20 20

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...Winter Weather Advisory until 7 am PST Thursday for east slopes
northern Cascades.

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