Weather Service Report


181 
FXUS66 KOTX 080558
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
958 PM PST Wed Dec 7 2016

.SYNOPSIS...
Dry and colder weather is expected tonight and into Thursday. 
Widespread light snow will overspread the region Thursday evening 
likely producing light to moderate valley accumulations and heavy
mountain accumulations through Friday. This snowy pattern will 
likely continue through early next week.

&&

.DISCUSSION...
Evening update: The winter storm watches have been cancelled for
most of the region as models continue to trend drier for the
Thursday night and Friday period. The watches for the East slopes
of the Cascades and Wenatchee area have been replaced with winter
weather advisories. Also...the timing of the Winter Storm Watch
for the Central Panhandle Mountains has been adjusted to run from
late Friday afternoon through Saturday evening.

There are a couple reasons why it has become apparent of the
models trending drier. First, the warm front is shearing as it
moves northward...resulting in less lift over most of Northeast
Washington and North Idaho compared to areas further south over
Oregon where models continue to show much higher qpf amounts.
Also...the lower level air mass is very dry with dew points this
evening in the single digits over Spokane and the Idaho Panhandle.
As the warm front lifts north easterly downslope 850mb winds off
the mountains will make it more difficult for the lower levels of
the atmosphere to completely saturate. With model qpf totals of
less than a tenth of liquid over most of the Columbia Basin,
Okanogan Valley, NE Washington and the Idaho Panhandle will
translate to snow amounts of only around an inch. New forecast
snow amounts can be found on our weather story at:

www.wrh.noaa.gov/FWC/wxstory.php?wfo=otx

As the warm front lifts north isentropic lift is still expected to
result in light snow accumulations Thursday night and
Friday...with higher amounts along the East Slopes of the
Cascades, Wenatchee area, and Waterville Plateau with low level
upslope flow and thus winter weather advisories are in effect.
Then a short waves progresses through the region Friday afternoon
and evening bringing a round of snow showers.

Moving on to overnight Friday night and Saturday...the low seen 
on infrared satellite near 45N/145W this evening will track 
through the area. Models are having a very difficult time with the
details of this with run to run changes with the strength and 
track as it comes through. A swath of accumulating snow...possibly
moderate to heavy...can be expected near and north of the low 
track but this track is uncertain. The westerly flow however will 
especially favor the Cascade crest and the Central Panhandle 
Mountains and thus the highlights have been extended into Saturday
for these areas.  JW

&&

.AVIATION...
00Z TAFS: Mid level clouds will continue around the KGEG-KSFF rea
and near KEAT with a decreasing trend this evening. Mostly clear 
and VFR conditions are forecast for much of the night, although 
patchy clouds may linger in the Cascade valleys due to moist 
upslope flow. East winds will be on the increase after 12z for 
KCOE, KPUW and KLWS. It will be dry. Meanwhile mid and high clouds
will increase from the south in the afternoon. Cigs are forecast 
to lower near KEAT and KLWS after 22z Thursday. /rfox

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane         9  25  21  28  23  30 /   0   0  70  90  70  70 
Coeur d'Alene   8  26  21  29  24  30 /   0   0  70  90  70  70 
Pullman        11  26  24  34  28  32 /   0  10  80  60  80  90 
Lewiston       13  30  28  38  29  39 /   0  20  80  50  70  80 
Colville       11  26  21  27  21  29 /   0   0  60  70  50  40 
Sandpoint       9  24  17  26  22  29 /   0   0  60  90  70  50 
Kellogg         4  23  17  29  25  30 /   0   0  80  90  80  90 
Moses Lake     11  27  20  30  20  31 /   0  10  80  50  50  40 
Wenatchee      17  26  20  28  21  32 /   0  20  80  50  50  50 
Omak            8  25  20  27  18  29 /   0   0  60  60  40  30 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Watch from Friday afternoon through Saturday 
     evening for Central Panhandle Mountains. 

WA...Winter Weather Advisory from 6 PM Thursday to 4 PM PST Saturday 
     for East Slopes Northern Cascades. 

     Winter Weather Advisory from 6 PM Thursday to 4 AM PST Friday 
     for Waterville Plateau-Wenatchee Area. 

&&

$$

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Western Regional Climate Center, wrcc@dri.edu