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fxus66 kotx 231040 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
240 am PST Thu Feb 23 2017

Synopsis...
a cooler and continued unsettled pattern will descend over the
region for remainder of the week. The main precipitation threat
will be mainly mountain based snow showers, but a stronger system
on Sunday may bring minor snow accumulations to the valleys and
basin. Temperatures will be cooler than normal for this time of
year with overnight lows in the teens and 20s and daytime highs
only in the mid 30s or so.

&&

Discussion...
today and tonight...compared to the weather of the past several
days, today's will actually be quite benign. The main focus today
will feature an elongating shortwave trough which is currently
located along a line from southeast British Columbia toward the
Waterville Plateau. This trough is expected to continue to drop southeast
though the day but it should do it quite slowly as a result of a
stronger trough plunging southward off the Washington coast. By afternoon,
the axis of the trough might only be as far east as a Sandpoint to
Yakima line and by tomorrow morning it may not be much farther
east than that. This suggests the forcing ahead of it will be
quite weak so it should not be a big weather maker. More important
will be the instability associated with the cold pool of air
aloft. 500 mb temperatures should be on par with what we saw
yesterday (around -35c to -37c) which when combined with daytime
heating will once again yield some steep lapse rates. However
unlike yesterday the moisture availability will be somewhat
lacking, especially for areas near and west of the trough. In
fact, the only areas which stand a fair chance of seeing
precipitation today will be over far southeast Washington and across the
southern half of the Idaho Panhandle. Moisture in this area will
pale compared to yesterday, however model soundings suggest there
will be enough to trigger some snow showers when subject to ascent
associated with the mid-level northwest flow. Any snow showers
which form should be fairly weak given the shallower instability
compared to yesterday. By evening and into tonight the shower
activity will wind down rapidly. Aside from the showers the main
challenge will be fog forecasting. The latest fog product is
showing a growing band of stratus and fog extending from the
northern Panhandle to the NE Columbia Basin near Davenport, Grand
Coulee and the West Plains. Much like yesterday this should burn
off with the daytime heating as the low level inversion should not
be strong under the presence of the upper level trough.
Temperatures today will continue their string of cooler than
normal readings. In fact, they should be anywhere from 1-5f cooler
than what we saw yesterday which equates to highs in the mid 30s
to lower 40s. Nighttime lows will likely continue the cooling
trend as drier air continues to filter in from the north-northwest. Look for
overnight lows in the mid teens to lower 20s for most valley
locations. Fx

Friday through wednesday: the inland northwest transitions to a
cooler, showery west-northwest flow. A long-wave trough settles
over the western U.S. And no deep moisture taps are indicated. Yet
shortwave troughs in that flow will still provide some risk for
showers, largely in the form of snow. Friday to Saturday a weak
shortwave passes. This will bring a threat light hit-and-miss snow
showers throughout the region Friday, before the main risk
retreats to the Idaho Panhandle and far southeast Washington into Saturday.

Between late Saturday night and Monday a better threat of snow
passes and it may cause some impacts to the late weekend and
Monday travel periods. With that said, model consistency is poor
to fair. Yesterday at this time models showed a weak, transient
wave passing in that time frame with limited snow amounts. Two
days ago models didn't show much at all passing. But today they
show a more robust system that tracks more directly across the
region. Still the moisture tap is not impressive with pwats around
0.15 to 0.30 inches (50-100% of normal). If the current track and
timing holds there would be an increase in snow across the region
later Saturday night into Sunday, before the threat shifts toward
the central and southern Panhandle and far southeastern Washington going
into Monday. Again if models maintain this depiction some light to
moderate snows are possible.

Tuesday and Wednesday the better threat of snow retreats to the
mountain zones, with more hit-and-miss snow shower chances across
eastern third of Washington and rest of Idaho. The night/early morning will
have some patchy fog threat. Otherwise expect a mix of clouds and
some sun. Temperatures will be notable much of the period, with
values below seasonal norms by some 6-11 degrees. So winter
continues. /J. Cote'



&&

Aviation...
06z tafs: a challenging, generally low confidence forecast on
hand tonight. Skies are clearing across the region allowing
radiational fog to form however a weak northwest push will bring drier in
from the north. The drier northwest flow will move into Ephrata and Moses
Lake first then Spokane-cd'a arnd 10z and continue south toward
Pullman. This is not a very strong push with winds generally near
5kts leading to low confidence if restrictions will form and when
they will clear. As of 06z...some fog was already forming in kcoe,
kdew, and ksff. These areas are more sheltered and will carry a
greatest risk for restrictions. Any low clouds will burn off
quickly thur morning with VFR conditions expected into the
evening before fog begins setting back in tomorrow night. /Sb



&&

Preliminary point temps/pops...
Spokane 34 19 33 19 34 22 / 0 0 20 10 0 40
Coeur D'Alene 36 17 34 16 34 20 / 10 0 30 10 10 40
Pullman 36 20 36 20 36 24 / 10 10 20 10 10 30
Lewiston 41 25 40 25 40 27 / 10 10 20 10 10 20
Colville 37 17 35 18 35 23 / 0 0 30 10 10 50
Sandpoint 36 19 33 17 34 21 / 10 10 20 10 10 50
Kellogg 33 19 33 18 33 24 / 30 20 30 20 20 50
Moses Lake 37 19 35 19 35 23 / 0 0 20 10 0 20
Wenatchee 36 19 33 19 34 22 / 0 0 30 20 10 20
Omak 36 18 33 19 33 22 / 0 0 20 10 0 30

&&

Otx watches/warnings/advisories...

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