Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 280918

Area Forecast Discussion
National Weather Service Spokane WA
218 AM PDT Fri Oct 28 2016

With one system exiting, today and tonight should see a break in
the wet weather, but more precipitation will move into the region
over the weekend and persist into next week. Temperatures will
remain relatively mild for this time of year, with no widespread
freezing conditions expected.


Today through Saturday night...A break in the active and wet
weather pattern is on tap for today...however this respite will be
short lived as satellite continues to depict a deep and stationary
upper trough over the Gulf of Alaska reloading to fling more wet
systems through the region this weekend. For today the major issue
will be widespread low clouds and areas of fog in the morning
hours with light winds and a saturated boundary layer air mass.
Low stratus ceilings will be dominant over the eastern reaches of
the Columbia Basin as weak upslope flow in the wake of yesterday`s
frontal passage continues this morning. Fog will be a major player
in the lowest elevations of the deep basin where clearing earlier
tonight has allowed cooling to the dew point under a nocturnal
inversion with light and variable winds. There is confidence that
much of this fog and stratus will break up late this morning as
the gradient shifts to a more northerly and thus dry trajectory.
By early to mid afternoon some sunshine is likely over most of
the region.

Tonight the break will continue as a weak upper level ridge
between storm systems continues to slowly transit the area. The
axis will cross into Montana late tonight and open the door for
another round of increasingly moist south or southwest flow off
the Pacific...manifesting itself as increasing and thickening high
clouds over the southern zones. This should serve to minimize a
return of fog and low clouds in the deep basin...but the northern
valleys where a longer period of overnight clear skies will
promote a return of valley fog and low clouds by dawn Saturday.

On Saturday models are in decent agreement in tracking the area
of enhancement visible on satellite this morning a few hundred
miles west of the Oregon Coast through the forecast area from
south to north. The main dynamic region of this system will stay
offshore and the overall trend suggested by the latest models is
a weakening system dragging a shearing occlusion through the
forecast area. This front will serve as a focusing mechanism for
the next fetch of Pacific moisture but the weakening trend and
stretching character suggest that while most locations will see
rain on will not amount to anything near what we
have experienced from the last storm...generally only a tenth of
an inch or two. This system will impact the region during the
afternoon on Saturday and into the evening with another inter-
system short wave ridge providing the next break period beginning
Saturday overnight and into Sunday. /Fugazzi

Sunday through Thursday: The Inland NW remains in an active
weather pattern with several opportunities for precipitation and
near to slightly above normal temperatures. Possible impacts:
Sunday through Tuesday occasional snow will be possible in the
mountain passes, particularly in Cascades and northern mountains.
However snow would have a better chance of sticking during the
night/early morning hours. A system passing around Monday may also
lead to some breezy conditions, but right now nothing that looks
strong enough to warrant any highlights.

Sunday...showers will be possible around the periphery of the
Columbia Basin, in proximity of a boundary near the southeast CWA
and within the mountains due to the southwest flow providing some
upslope shower threat. Early Sunday evening and
occluding system comes in from the southwest and ramps up the
precipitation chances. There are still some disagreements on the
precise track and location of the steadier precipitation. The best
threat will be over southeastern WA through the central to
southern Panhandle. However half the models suggest a broad threat
comes up through the Columbia Basin and northern mountains through
Sunday night too, with the rain stalling across the northern and
eastern CWA through mid-Monday before retreating to the mountains.
Some moderate rain amounts are possible and it could help push
October the wettest on record. This passing system may also come
with breezy conditions Monday. I increased speeds over the
previous forecast, especially across the Columbia Basin into the
Spokane area and Palouse. Most guidance shows a tightening south-
north gradient coming up from the south through the day, before
slackening through evening. Details may change but right now I
have gusts near 20-30 mph.

Monday night...previous model runs kept the main shower risk in
the mountain zones. Yet some newer runs bring another quick-moving
shortwave in to renew rain chances. Consistency has been poor. So
while I raised PoPs some I didn`t bring them to likely yet.
Tuesday...another shortwave slips by in a more westerly flow. This
will keep shower chances alive, with the highest risk in the
mountains and the least risk in the lee of the Cascades and deeper
Columbia Basin.

Through Sunday night snow levels are projected to be between
5-7kft, before dropping to between 4.5-5.5kft Monday into Tuesday.
So some snow may fall in the some of the mountains passes during
this period, particularly near the Cascades and northern mountains.

Between Tuesday night and Thursday...the pattern starts to amplify
with the long-wave trough over the eastern Pacific reloading. The
flow becomes increasingly south-southwest and another atmospheric
river/moisture plume is drawn up the Pacific Coastline. In this
set-up models tend to keep the highest precipitation threat over
the Cascades westward, with secondary chances across the northern
mountain zones. Areas to the east/southeast of these locations
have transient chances with the passing shortwaves potentially
stretching and/or weakening. There are still modest model
disagreements on all the details, but loose consensus supports
the aforementioned generalizations. Snow levels rise to between
5-7kft Tuesday into Wednesday and toward 6-8kft Thursday. /J. Cote`


06Z TAFS: The band of rain showers continues its slow eastward
track, and should be mostly in north ID by midnight. A mix of
MVFR to VFR conditions with local IFR will continue for all TAF
sites. LIFR/IFR stratus cigs and possibly fog is expected to
develop overnight tonight and continue through 18z Friday.
Cigs will likely dissipate in the morning with thinner high
clouds moving in during the afternoon.


Spokane        52  40  51  41  51  42 /  10   0  50  40  20  60
Coeur d`Alene  53  40  52  41  51  42 /  10   0  60  50  30  70
Pullman        56  43  54  43  54  44 /   0   0  70  60  50  70
Lewiston       59  45  58  46  58  47 /   0   0  70  60  40  70
Colville       52  38  51  40  51  39 /  10   0  60  40  20  60
Sandpoint      49  36  50  39  49  38 /  10   0  60  60  30  60
Kellogg        50  38  51  40  49  40 /  10  10  70  60  40  80
Moses Lake     56  40  54  40  54  40 /   0   0  40  20  20  50
Wenatchee      55  43  54  40  52  41 /  10  10  50  20  20  50
Omak           54  41  54  39  53  38 /  10   0  60  30  20  40




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