Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 250013
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
413 PM PST Tue Jan 24 2017

.SYNOPSIS...
Two weather disturbances will move through the region. the first
this afternoon and this evening and the second Wednesday. This
will result in areas of light snow showers or snow flurries across
the eastern portion of the forecast area. By Wednesday night and
Thursday strong ridge will build over the Pacific Northwest. This
result in cooler weather, with an abundance of low clouds and fog
in the valleys through the weekend. The occasional weak wave may
result in some light snow chances but overall drier weather is
expected.


&&

.DISCUSSION...
Tonight through Thursday: A High amplitude ridge is currently out
near 130W with a closed low over the central Plains. This puts
the Pac NW in a mainly dry northerly flow. The ridge will begin to
nose into the region this evening, then slowly flatten out by
Thursday afternoon. Clear skies and light winds have resulted in
a strong surface inversion and widespread low level stratus and
localized fog. This is not likely going to change for the next few
days. As a matter of fact with the ridge strengthening over the
region tonight and Wednesday the inversion will only get stronger.
There has been some late afternoon clearing the past few days,
but with the inversion strengthening even that small break will
likely go away. Temperatures will see little diurnal change with
highs in the lower 30s and lows in the upper 20s. There will be a
couple of weak upper level disturbances that will track south
along the ID/MT tonight and Wednesday. The one moving through the
region this afternoon did not have enough dynamics or mid level
moisture for any widespread precipitation. However in the stratus
layer near the surface there was enough isentropic lift and
orographic lift to squeeze some light snow flurries and locally
some light freezing drizzle. This is expected to continue through
this afternoon and early this evening. The next wave will drop
through tonight and early Wednesday with the same results.
Accumulations will be very light from a trace to maybe a half of
an inch of light snow. If you want to see the sun the next few
days you can head to the mountains where they will be above the
inversion. Tobin

Thursday night to Tuesday: Very limited opportunities for
precipitation mark an otherwise dry, cooler than normal period.
First between Thursday night and Saturday night high pressure
dominates the pattern from the surface to the mid-levels. Largely
this will serve to hold some low clouds and some patchy fog in
place over most of valley/basin locations under about 3000-4000
feet, with more transient middle to high clouds over the mountains
above that elevation. The exception may be toward the lower
Columbia Basin into the Palouse, where a southeasterly flow may
keep some of those low clouds at bay, especially as the period
progresses. How solidly the low clouds remain in place across the
remainder of region is not yet certain, but if they become
established early on there is little to mix them out. While high
pressure will be in control, some mid-level waves do pivot over
the top of the ridge from west-northwest to southeast between
Thursday night and Friday. This may be enough to ring out some
flurries/isolated snow showers/freezing drizzle from the low
clouds. The best threat will be around the north and eastern rim
of the Columbia Basin into the north and eastern mountain valleys.
Yet these are not expected to amount to much if anything falls at
all.

Between Sunday and Monday models dampen the ridge, at least
briefly, bringing a shortwave trough in from the Pacific and some
threat of mainly light precipitation. There are some differences
in its timing and track. Generally some risk of snow comes to the
Cascades Sunday, though it may hold of until Sunday night when
the risk expands across the northern and eastern mountains too.
Small chances may also come to the Columbia Basin, but the risk is
too low to include at this time. Furthermore, if the system
tracks too far north even the northern counties may not see much,
if anything. Either way at this time is does not look strong. The
main thing to keep a watch on is the potential for some mixed
precipitation (i.e. freezing rain/sleet) over the southeastern CWA
should a precipitation threat come to that region. The surface
temperatures appear will remain below freezing, while most models
show 850mb temperatures warming to between +1 and +3 C in that
region (i.e. a potential melting layer). The ridge rebounds Monday
night into Tuesday, drying the area out (but the next system and
broader precipitation chances starts in Tuesday night into
Wednesday). /J. Cote`


&&

.AVIATION...
00Z TAFS: Little change to the over all thinking from previous
discussions...fog and stratus will continue to hamper air
operations for the next 24 hours. A weak wave currently moving
through the southeast zones will result in a slight chance -shsn
at KPUW/KLWS through 04-06z. Otherwise MVFR/IFR conditions for
mainly ceilings will be widespread through the night. A second
wave is expected to take a similar path later tonight and
Wednesday. This will result in another round -shsn precipitating
out of the stratus. And as we saw today that resulted in rapidly
changing conditions. KEAT looks to remain VFR through the
period...although there will be a low chance for lower cigs near
sunrise. Tobin


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        29  31  22  30  21  30 /  20  20  10  10  10  10
Coeur d`Alene  29  33  22  30  21  31 /  30  30  20  20  20  20
Pullman        27  31  23  31  21  32 /  30  30  20  20  10  10
Lewiston       30  35  25  35  24  36 /  30  20  20  20  10  10
Colville       31  32  19  29  21  31 /  10  10  10  10  10  10
Sandpoint      24  32  22  31  22  32 /  30  20  10  20  20  20
Kellogg        28  31  22  29  22  32 /  50  40  40  20  10  20
Moses Lake     27  31  22  30  21  31 /   0  10  10  10  10  10
Wenatchee      21  30  22  28  22  29 /   0   0  10  10  10  10
Omak           29  30  20  30  22  31 /   0  10  10  10  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$



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