Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 212321
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
321 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 NW. 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 NW 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 WA to half to three quarters of an inch in
extreme eastern WA 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...
00Z TAFS: Rain band will remain over the region through the
period with light winds. Cigs and vsbys will be fluctuating with
more intense showers or increased fog as the rain decreases.
Expect predominantly MVFR conditions with areas of IFR. The HRRR
shows a decrease in rain between 08z-13z for KMWH and KEAT. Rain
will persist at KPUW and KLWS into Wednesday morning, before
shifting northward in the afternoon. /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...
ID...None.
WA...None.

&&

$$



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