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fxus66 kotx 111839 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
1039 am PST Wed Dec 11 2019

Synopsis...
bands of light snow will spread across the eastern third of
Washington and the Idaho Panhandle this morning which could lead
to a slick morning commute. A much stronger system will move in
fast on this storms heels. This next one will be a warmer system,
however it will carry significantly more moisture and will likely
lead to a heavy snow in the mountains. The threat of the snow will
diminish Thursday night. The weather will remain unsettled into
the weekend however no significant storms are expected at this
time.

&&

Discussion...
today...a relatively progressive shortwave trough has triggered a
broad band of snow extending from the Idaho Panhandle southwest
toward the Tri-Cities this morning and this will be the main
feature at least through mid-morning. All the short-range models
are doing fairly well with the placement of the precipitation
shield and track it into extreme southeast Washington and the southern
half of the Idaho Panhandle by mid-morning. While the handling of
the precipitation shield is good, the low-level thermal fields are
a little too warm and as such we expect most locations to see
snow, rather than some rain over the lower Columbia Basin and
possibly in the lc valley. Snow totals will generally range from 1
to 2 with local 2-4 inch amounts over the Panhandle mountains. For
the Spokane/cda are we expect the precipitation threat to dwindle
around sunrise. Roads could be slick for the morning commute so
motorists are advised to allow a little extra time. While the
threat of precipitation will decrease as the dendritic layer dries
out from the west, we suspect plenty of moisture will remain
trapped in the boundary layer, which suggest widespread fog and
low clouds will persisting over many locations into the afternoon.
The next storm system is expected to move into central Washington
by afternoon, so the break between precipitation events will be
brief. The next round of precipitation will be warmer than the
current one so we expect to see a gradual transition from snow to
rain, or just rain for much of the lower Columbia Basin, while
farther north the event will start as more light snow. Then things
begin to pick up intensity wise this evening, especially near the
Cascade crest due to the development of offshore flow into the
dendritic layer. Fx

Tonight through Thursday night: models continue to show a strong
jet moving into Oregon with several waves along and north of the
jet bringing rain and snow to the area. Strong west to southwest
flow will bring added upslope lift into the Cascade crest and
Idaho Panhandle where heavy snow accumulations are expected in the
mountains and will be upgrading the watches to warnings. The
first wave arrives this evening as a warm front brings isentropic
ascent and widespread precipitation. Lingering cold air along the
east slopes and northern valleys should result as precipitation
beginning as snow before milder air moves in by Thursday morning
except possibly the Methow Valley where cold air often has a hard
time mixing out. For the northern valleys snow totals are expected
to be highest near the Canadian border around Metaline Falls and
Ione where 4-5 inches is possible while milder air will be quick
to move into Deer Park and Athol with a quick change to rain this
evening. For the Okanogan Highlands and NE Washington mountains will be
issuing a Winter Weather Advisory mainly for areas north of
Keller, Springdale, and Deer Park. Precipitation is expected to
fall as valley rain and mountain snow along and south of the I-90
corridor. This wave exits Thursday morning with showers confined
to mainly the Idaho Panhandle and Cascades on Thursday.

Another wave will bring a resurgence of precipitation Thursday
evening and overnight but strong mid level westerly flow should
keep the bulk of the precipitation still in the Cascades and Idaho
Panhandle. This second wave will also have a surge of wind with
it as 850mb winds increase to 40-50 kts over southeast Washington into
the central Panhandle mountains producing localizing blowing snow
in the mountains, and gusty winds near the foothills of the Blue
Mountains and Palouse. Jw

&&

Aviation...
18z tafs: the forecast area is in between weather systems this
morning. Plenty of boundary layer moisture was left behind after
the rain and snow moved out of the area. Right now we are seeing
a short period of dry air advecting into the area from the west.
At best this will be short lived as high level moisture from the
incoming storm tonight is already moving into the area. This will
result in wildly fluctuating cigs/vsby for all of the taf sites
through this afternoon. Some light -fzra/ice pellets will be possible at
kgeg/kcoe through about 20z but accumulations will be very light.
Most if not all taf sites will see a short window of MVFR/VFR
conditons between 21z-00z. Then cigs will begin to decrease as
the next warm front moves through the region. Precipitaiton will
begin at keat between 00z- 02z and should be over to
kgeg/ksff/kcoe/kpuw between 02-04z. Temperatures are expected to
warm up enough for the precipitation to be all -ra, with the
exception at keat where
-ra/-sn mix will be possible. Tobin





&&

Preliminary point temps/pops...
Spokane 36 35 43 33 40 28 / 50 90 40 40 10 10
Coeur D'Alene 36 36 41 33 38 30 / 60 100 70 60 20 10
Pullman 39 37 45 35 41 30 / 60 80 60 50 30 20
Lewiston 45 39 50 37 46 34 / 60 80 50 50 30 20
Colville 35 31 39 30 40 25 / 40 90 40 40 10 0
Sandpoint 35 33 39 33 37 30 / 60 100 90 70 30 10
Kellogg 37 34 40 33 37 30 / 80 100 90 90 60 40
Moses Lake 36 35 47 32 45 25 / 40 60 30 20 10 10
Wenatchee 35 32 43 31 41 28 / 40 60 50 30 10 10
Omak 33 30 39 28 38 26 / 30 80 40 20 10 10

&&

Otx watches/warnings/advisories...
Idaho...Winter Storm Warning from 7 PM this evening to 10 am PST Friday
for central Panhandle mountains-northern Panhandle.

Washington...Winter Weather Advisory from 7 PM this evening to 7 am PST
Thursday for northeast mountains-Okanogan Highlands.

Winter Storm Warning from 1 PM this afternoon to 10 am PST
Friday for east slopes northern Cascades.

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