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fxus66 kotx 212216 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
216 PM PST Tue Nov 21 2017

Synopsis...
expect wet and mild weather through the week as a series of storm
systems brings several rounds of precipitation to the inland northwest. Snow
levels will be quite high through Thursday allowing motorists to
travel over mountain passes on wet pavement. Snow levels will
begin to lower just as travelers are heading home Friday into the
weekend. Windy conditions are expected Thursday across the
exposed areas of the basin and into the Spokane area and Palouse.

&&

Discussion...
tonight and wednesday: the mild and moisture laden southwest
flow aloft will remain over the inland northwest through the period
as an atmospheric river sends high pwats of near an inch east
of the Cascades. Isentropic lift coupled with a warm front
lifting through the region will be the focus of the precipitation.
Temperatures and snow levels are slowly rising. May see some high
elevation snow in the Pasayten Wilderness and far north Idaho,
but rain will be the main precipitation. The threat of a wintry
mix in the lower elevations has seemed to modify as temperatures
warm. The warming will continue overnight. Increased southwest
winds will help increase downslope drying conditions over north
central Washington overnight while the rain persists over
southeast Washington and north Idaho. The rain band will shift
north again on Wednesday as another warm front pushes through the
region. Over the next 24 hours, the highest precipitation amounts
will be near the Cascade crest and over north Idaho mountains with
1-2" rain possible, while the low lands expect to see around 0.1"
in north central Washington to half to three quarters of an inch in
extreme eastern Washington to north Idaho. While the high snow pack will
absorb a bulk of this moisture, runoff will increase and expect
rivers and streams to be on the rise in the Cascades and north
Idaho. In fact, recent rises on Paradise creek in Moscow has
prompted the issuance of a Flood Watch there for the next several
days. Where the rain does taper off overnight, anticipate patchy
fog with reduced visibilities. Temperatures will warm several
degrees warmer on Wednesday. /Rfox.

Wednesday night through next Tuesday...a remarkably active
weather pattern is depicted by all the latest models for the
remainder of the week. Through this weekend a persistent and
reloading offshore trough will direct a series of deep Pacific
moisture plumes into the area bringing periodic bouts of generally
rain in the valleys and midslopes with snow confined to the
higher mountains. There will be some break periods...for the basin
at least...the mountains will be subject to random showers even
during these breaks. Friday and Sunday appear to be the least wet
and quietest days during this mild southwesterly flow regime. On
or about Sunday night or Monday the offshore trough will eject
through the region bringing more precipitation and a lowering of
snow levels to the extent that further precipitation will be
valley rain during the afternoon and evening hours and possibly
non-accumulating snow in the overnight and early morning hours.
Way out around late Monday or Tuesday models suggest a quieter
ridge building over the region...but this break may be short
lived.

In the near term, Thanksgiving day will likely be wet for most
locations as a cold front enhances a moisture fetch into
widespread rain ahead and along it as it transits the region.
Thursday afternoon rain will taper off from west to east...however
winds will become an issue with solidly breezy to windy sustained
winds and a potential for gusts in the well mixed Post-frontal
air mass to approach 50 mph on the exposed terrain of the eastern
Basin. A Wind Advisory may need to be issued for much of the
Columbia Basin for Thursday afternoon and evening. This front will
allow snow levels to drop from about 8000 feet Thursday to around
5000 feet Friday...but a weak short wave ridge will be building
into the region so precipitation should be tapering off by then.
Travelers returning to home to the other side of the passes may
encounter some localized minor snow accumulations on Friday from
upslope snow showers...but these impacts should be limited to the
highest elevations near the pass summits. /Fugazzi

&&

Aviation...
18z tafs: a swath of rain will be over the region for much of the
period. At keat, light upslope winds will give way to IFR cigs
with the rain. As it tapers off, may see some cigs improvements.
Kmwh, klws and kpuw should stay primarily VFR with areas of MVFR
conditions with the moderate bands of rain. In the kgeg/kcoe
corridor, LIFR vsbys/cigs should be lifting as the rain arrives
with improvements to IFR to local MVFR through the rain event.
Winds turn SW by early morning as the rain shield exits, which
should improve conditions although upslope stratus/fog is possible
as well to bring conditions back down again. /Rfox.

&&

Preliminary point temps/pops...
Spokane 41 53 46 55 36 45 / 100 90 50 90 30 10
Coeur D'Alene 41 53 45 55 36 45 / 100 90 50 100 40 10
Pullman 44 57 46 57 37 48 / 100 70 30 90 70 0
Lewiston 45 58 48 61 40 52 / 100 80 20 50 60 0
Colville 34 46 40 53 33 44 / 80 70 70 70 20 10
Sandpoint 36 47 41 51 35 42 / 100 90 80 100 40 20
Kellogg 39 49 42 51 34 41 / 100 90 50 90 80 40
Moses Lake 37 52 43 59 35 50 / 70 40 30 30 10 0
Wenatchee 36 49 41 54 35 47 / 50 50 40 40 10 10
Omak 37 48 41 54 34 45 / 70 30 50 50 10 10

&&

Otx watches/warnings/advisories...
Idaho...none.

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