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Area forecast discussion 
National Weather Service Spokane Washington
347 am PST Thursday Nov 26 2015

chilly temperatures and clear skies are expected today into Friday
as strong high pressure builds over the Pacific northwest. Light
winds and a strengthening inversion will increase the potential
for air stagnation this weekend. We will also have the potential
for areas of fog and low clouds over the weekend into early next
week. The next chance of precipitation is expected next Wednesday
with the arrival of a frontal system.



Today through saturday: winds have decreased over the majority of
the inland northwest with most reporting sites carrying less than
10 mph. The corridor from Omak to Mansfield to Ephrata remains the
exception as chilly north winds continue to funnel through the
Okanogan Valley. We will see the northerly surface pressure
gradient weaken today as a strong upper high builds over
Washington and British Columbia. The increasingly stable pattern
will be the primary subject of our discussions the next several
days. The models are in good agreement that mid-level subsidence
under our developing Rex block will build an increasingly strong
inversion. Our current surface dewpoints are dry, so we won't see
any fog this morning, but as our north winds continue to weaken,
look for our humidity levels to gradually increase. Patchy fog may
be possible Friday morning in the lower Columbia Basin and along
portions of the Snake River. By Saturday morning, patchy fog may
develop in our sheltered valleys of northeast Washington, north
Idaho, and along the Clearwater/snake rivers as well as the basin.
Temperature forecasting will become increasingly tricky Friday
into the weekend as the inversion strengthens. Low elevations may
remain in the upper 20s and low 30s in the afternoons while the
mountains have the potential to warm into the upper 30s to low
40s. The strong inversion and light winds Thursday night through
the upcoming weekend has prompted the issuance of an air
stagnation advisory for the potential of increasing concentrations
of air pollution.

Sunday through wednesday: the dry, stable and cool weather will
prevail through the remainder of the weekend and into Monday with
areas of low clouds/fog and strong low level inversions. Then by
Monday night, a pattern change is expected as the blocking upper
level ridge weakens. An enhanced northern Pacific jet will take
aim on the Pacific northwest with a string of weather disturbances
heading inland. The first of these disturbances is the most
difficult to track. The models show disagreement on if the flow
will continue to split near the West Coast or become consolidated.
The GFS and Canadian continue to follow the consolidated solution
on bringing this weather disturbance on a northern Route toward
western Washington by Monday night and then weakens it quickly.
The European model (ecmwf) takes a southern Route with the ridge remaining strong
over the inland northwest. Despite the track of the initial
feature, the sensible weather will reflect not much precipitation
if any; either an increase of clouds and just possible mountain
showers east of the Cascades with the more aggressive solution for
Tuesday/Tuesday night. Meanwhile, a large scale trough will
develop in the Gulf of Alaska allowing a flow of weather
disturbances to move into the region. The GFS continues the
progressive forecasts with a steady onslaught of moisture in the
southwest flow heading across the region for Wednesday into
Thursday. The European model (ecmwf) follows similar trends, but is a bit slower
with the strength of the ridge aloft, but does introduce possible
precipitation by next Thursday. Overall, anticipate temperatures
will gradually warm to seasonal levels, with the erosion of the
cold air mass and the arrival of the Pacific weather systems. Will
opt for a blend of the model solutions and show an increase in
precipitation chances starting by late Tuesday and steadily
increasing through midweek. /Rfox.


12z tafs: strong high pressure will produce clear skies over the
inland northwest for the next 24 to 36 hours. VFR conditions are
expected at all airports this Thanksgiving Holiday. /Gkoch


Preliminary point temps/pops...
Spokane 31 15 30 18 32 17 / 0 0 0 0 0 0
Coeur D'Alene 30 14 31 18 33 19 / 0 0 0 0 0 0
Pullman 33 15 31 17 32 18 / 0 0 0 0 0 0
Lewiston 35 18 33 20 33 22 / 0 0 0 0 0 10
Colville 34 12 34 13 37 16 / 0 0 0 0 0 0
Sandpoint 31 17 31 18 34 17 / 0 0 0 0 0 0
Kellogg 30 14 32 16 34 18 / 0 0 0 0 0 0
Moses Lake 36 14 32 17 33 18 / 0 0 0 0 0 0
Wenatchee 35 20 33 21 33 21 / 0 0 0 0 0 0
Omak 34 17 33 16 35 17 / 0 0 0 0 0 0


Otx watches/warnings/advisories...
Idaho...air stagnation advisory from 9 PM this evening to noon PST
Monday for central Panhandle mountains-Coeur D'Alene area-
Idaho Palouse-Lewis and southern Nez Perce counties-
Lewiston area-northern Panhandle.

Washington...air stagnation advisory from 9 PM this evening to noon PST
Monday for east slopes northern Cascades-lower Garfield and
Asotin counties-Moses Lake area-northeast Blue Mountains-
northeast mountains-Okanogan Highlands-Okanogan Valley-
Spokane area-upper Columbia Basin-Washington Palouse-
Waterville Plateau-Wenatchee area.



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