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Area forecast discussion 
National Weather Service Spokane Washington
455 am PDT Thursday Oct 30 2014

Synopsis...
a slow moving frontal system will spread clouds and rain across
the region today and Friday, with the highest rain chances limited
to the Cascades. This precipitation will then spread east into
eastern Washington and north Idaho on Friday. Rain in the Idaho
Panhandle will likely linger into Saturday. Cool and unsettled
weather is expected to continue into next week.

&&

Discussion...
today and tonight: the challenges for the first 24 hrs of the
fcst will be straightforward, centered around pcpn amnts and
areal coverage of fog and low clouds. Much of ern WA and north Idaho
has been dealing with residual sfc moisture left from the pcpn
event from tues and tues nt, with clearing skies aloft allowing
for efficient maintenance of fog and low clouds. The regional
radar mosaic shows light stratiform pcpn spreading north across
cntrl WA associated with ascent over a warm front boundary along
the Oregon/WA border. It is this pcpn threat that will end any
dense fog this morning. But with sfc obs showing no more than a
hundredth or two reaching the sfc, pcpn amnts today will not be
impressive...likely following the overall driest GFS model. We
trended heavily toward this solution and tried to limit the
heavier amnts to the Cascades for later today and tonight. It's
the Cascade zone that will see the cold front stall in place,
prolonging the pcpn threat. Farther to the east, including the
Idaho Panhandle and southeast WA, only light amnts of rain, if any, can
be expected as the warm front lifts quickly north. Bz

Friday through sunday: a moist but weakening cold front will
cross through the inland northwest on Friday bringing periods of
light rain. The front will cross the Cascades Friday morning then
inch its way into eastern Washington by early evening and to the Idaho/Montana
border near midnight. The heaviest rainfall amounts are expected
near the Cascades early Friday when a fetch of subtropical
moisture is still streaming northward ahead of the front. As the
front begins its eastward migration, it will begin to lose its
structure and the deeper moisture will be pinched off bringing
pwats down from around an inch to 0.75". Consequently,
precipitation will be most intense Friday morning near the
Cascades and trend lighter across the Columbia Basin and upon
reaching the Idaho border. The exception will be in the northern
mountains where southerly flow will assist in lifting the
moisture into the higher terrain. High temperatures will be near
50f for most locations except southeastern Washington and the lower Idaho
Panhandle which will have the best chance for some sun and mixing
increasing their chances to warm into the 60's.

A significant slug of energy will eject from the base of the trough
over Southern California Friday night and track northeast through
Nevada, southern Idaho, and Montana over the weekend. Models
continue to support a second area of low pressure deepening ahead
of this wave. Strengthening cyclonic flow within the deepening low
will and renew lift along the boundary and bring a narrow but
intense region of precipitation between northwest Montana and NE Oregon
which will likely cross through portions of the Idaho Panhandle and
perhaps far southeastern Washington. There is decent agreement related to
the large scale picture but each model has a different depiction
regarding how far west to expand the rainfall. Attm, Shoshone
County to the Camas Prairie is most favored to be in the axis of
heavier precipitation with lighter amounts extending toward the Washington
border. Pops in the Camas Prairie and central Panhandle mtns also
reflect increasing northwest (upsloping) flow being drawn into
the low. In the Idaho Panhandle and blue mtns, snow levels will
start off high (6500') but will come down Saturday night near 4500
feet as cooler air is drawn into the low. By the time snow levels
come down, most precipitation will be departing to the east but we
cannot rule out a short period of light snow near Lookout Pass
Sunday morning. The Cascades and western basin will generally
experience a break in the wet weather through much of the weekend
but areas of fog and stratus are possible following the rainfall
Friday.

Monday through wednesday: a fire-hose of atmospheric moisture will
become aimed at the northwestern US bringing several more rounds
of precipitation, gusty winds, and mild temperatures. The first
round of precipitation will arrive Monday with the potential for
moderate to heavy amounts along the Cascade crest and mountains
over northeastern Washington/nrn Idaho. Lighter rainfall will spread into the
Upper Basin but strong westerly flow accompanying the pattern will
keep amounts very light due to shadowing off the Cascades. The
stream of moisture looks to get shoved south into northern Oregon
briefly on Tuesday with the passage of a shortwave trof but
quickly rebounds back northward and potentially migrates north
into southern British Columbia by midweek as high pressure attempts to build
over the northern rockies. Confidence regarding the details are
far from certain and even as the firehose buckles north, it
appears the northern Cascades and mountains along the British Columbia border
will stand a good chance to remain in the wet weather pattern.
Snow levels with this pattern will remain Above All pass levels
accompanied by above normal temperatures. /Sb

&&

Aviation...
12z tafs: with light rain spreading north across ern WA and north
Idaho, any remaining strong near-sfc inversions capping a
fog/stratus lyr are weakening and allowing VFR conditions to
prevail. The rain is expected to be light, with the heaviest amnts
near the Cascades including keat. Even so, ceilings with rain are
expected to go no lower than MVFR.

&&

Preliminary point temps/pops...
Spokane 54 44 56 41 49 34 / 30 20 30 50 20 10
Coeur D'Alene 55 42 58 42 47 34 / 20 10 20 70 60 20
Pullman 59 46 59 42 48 35 / 10 10 10 70 60 20
Lewiston 64 47 64 46 50 39 / 10 0 10 80 60 20
Colville 52 42 56 40 50 33 / 60 30 70 50 20 10
Sandpoint 51 39 57 40 47 35 / 30 10 20 60 60 30
Kellogg 53 41 59 40 45 35 / 10 10 10 70 80 40
Moses Lake 56 45 56 41 55 35 / 60 30 60 20 10 10
Wenatchee 51 45 55 39 53 36 / 90 70 90 10 10 10
Omak 52 42 53 37 50 33 / 80 80 90 20 10 10

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&

$$

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