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Area forecast discussion 
National Weather Service Spokane Washington
244 PM PDT Friday Oct 24 2014

Synopsis...
a warm front will lift through the region tonight with a band of
rain. A strong cold front passage Saturday night and Sunday will
produce very windy conditions with gusts in excess of 40 mph. The
pattern will continue to be active into early next week. This
includes the potential for widespread rain into early next week as
moisture associated with former typhoons makes its way toward the
Pacific northwest.

&&

Discussion...

Tonight and Saturday...warm front comes up from the south tonight
spreading clouds and precipitation from south to north. Saturday
is a bit more complicated as the warm front more or less exits
into southern British Columbia and a cold frontal zone associated
with the same low pressure system the exiting warm front is tied
into moves inland. A surface low in the vicinity of where both
these fronts tie into low pressure system moves onto the coast as
well. The result of this scenario is an increase in the surface
pressure gradient and the moisture along and ahead of the cold
front invading the sky from the west and keeping a significant
amount of cloud cover in the forecast along with increasing
precipitation chances through the day Saturday. Winds increase
with a warming trend as well. /Pelatti

... Winds are expected Saturday night and Sunday...

Saturday night through Monday night...the progressive pattern
will continue through this portion of the forecast and the models
seem to be doing a good job keeping up. A cold front will move
through the forecast area Saturday night, then stall along the
Montana border Sunday morning. The atmosphere will destabilize
ahead of the front, and with ample moisture available it will
result in widespread showers for the entire forecast area. Model
guidance is picking up on enough surface based and mid level
instability to support a slight chance of thunderstorms from about
Pomeroy northeast to about Mullan Pass. Thunderstorms are not
overly common this time of year and especially at night. This may
end up with some very heavy showers, but this much instability
thunderstorm potential can't totally be ignored. Localized
moderate to heavy rain and snow showers will be probable through
early Sunday morning. Snow levels will drop behind he front to
between 4k-5k feet. The higher mountains could pick up several
inches of snow.

Another concern will be winds and wind gusts through the night
and into Sunday. A deep surface low will move off the Pacific and
northeast into b.C. This is a perfect set up for the inland
northwest to get gusty winds. The surface gradient will increase
to 10-12 mb between Portland and Kalispell, and 850 mb winds
increase to between 40-50kts. Mixing associated with the front
should have no trouble mixing these higher winds down to the
surface. Sustained winds of 20-35 mph with gusts 30-40 mph will be
possible. An area of concern will be the eastern Columbia Basin,
the Palouse and the foothills of the Blue Mountains where model
guidance is showing winds 25-40 mph with gusts 40-50 mph. This
will either meet Wind Advisory criteria or be very close and an
advisory will be issued with the afternoon package.

Rain and mountain snow showers will continue through Sunday
evening with the focus closer to the higher terrain of the the
Cascade crest, the northern Washington and Idaho Panhandle
mountains. However showers will be possible just about anywhere
outside of the deep basin through sunset. Winds will remain strong
and gusty through Sunday but will begin to decrease through Sunday
afternoon.

Weak and short lived high pressure will build into the region on
Monday. Some lingering mountain showers will be possible in the
west-northwest flow but the forecast should be mainly dry. The
next frontal system will begin to move into the Cascades by Monday
evening. Warm over-running precipitation will begin along the
Cascades around 06z Tuesday and slowly push across the forecast
area the remainder of the night for another round of valley rain
and high elevation snow. /Tobin

Tuesday through friday: the active pattern will continue,
especially early this period as the remnants of Tropical Storm Ana
come into the Pacific northwest, but models start to disagree by
the second half of the work week. On Tuesday morning low pressure
is centered near northern Vancouver Island, with a warm front
draped across north-central Washington through the lower Idaho Panhandle.
This set-up provides ample isentropic lift with a tap into a
subtropical moisture plume (with pwats around 150-190% of normal),
until that low pressure center and a westerly 100kt jet pushes
inland. This will lead to the likely threat of rain during the day
outside of the deeper basin, before the threat backs against the
Cascade crest and retreats to the eastern mountains Tuesday night
into Wednesday. Precipitation could be moderate to locally heavy
in the Cascades and northeast Washington and north ID, especially on
Tuesday.

Snow levels linger around 4-5kft in the morning, then rise to
around 5-7kft in the afternoon over a large part of the region.
The main exception could be across the Canadian border counties
where they may linger around that 4-5kft mark. So if precipitation
starts early enough there could be some snow accumulation around
the passes, with the best threat of it lingering through the day
around Sherman Pass where the warmer air may not reach. With this
said, there is still a lot of room for model changes but it is
something to monitor.

From Wednesday night into Friday a long-wave trough deepens
across the eastern Pacific and nudges toward the Pacific northwest
coast. The southwest flow increases going through this period,
with a warm front lifting back north around late Thursday or
Thursday night, followed by shortwave disturbances skirting by the
Cascades. Models disagree over whether to hold the higher
precipitation threat associated with these features in the
Cascades or to expand it over most of eastern WA/ID. I left at
least a slight chance in most spots from Thursday, with higher
pops in the Cascades and mountains. I expand higher pops eastward
again Friday as the ridge axis shifts east of the Idaho/Montana border and
there will be more opportunity for any impulses to actually cross
the region and given those better precipitation chances. Given the
overall set-up with the trough offshore and ridge over the
northern rockies, I also have some patchy fog in the forecast
largely for the night and morning hours across the sheltered
northeast valleys and out into some of the typical Spokane/c'da
area spots (along the river and out toward the west plains).

As for temperatures, values remain near to slightly below normal
early this week. Then values start to warm above normal with the
building ridge and southwest flow ahead of the offshore trough,
especially toward Thursday into Friday. The only possible caveat
will be the potential for any fog/stratus holding temperatures
back from reaching their full potential. /J. Cote'

&&

Aviation...
18z tafs: little change to the previous forecast timing with VFR
conditions expected at all taf sites through 00z with cigs steadily
lowering through the day ahead of a warm front, currently over
Oregon and central Idaho, which will move north overnight. The
front will develop a east- west band of rain which will hit lws
mwh eat and puw around 00z and push into the geg sff Coe area
around 02z. Once the rain begins...we expect to see some clouds
develop below 030 but we don't expect prevalent cigs at MVFR
levels. The one exception will be at eat due to proximity to
Cascades combined with upslope flow. The warm front will deliver
about 6 hrs of precipitation to most sites (persisting a little
longer at eat) with improving conditions after that.

&&

Preliminary point temps/pops...
Spokane 44 63 43 53 36 50 / 60 10 80 30 10 10
Coeur D'Alene 42 64 42 52 34 49 / 50 10 90 30 20 20
Pullman 45 66 43 50 38 50 / 50 10 70 30 20 20
Lewiston 44 70 47 55 41 56 / 50 10 60 20 20 10
Colville 42 62 44 53 34 51 / 70 20 80 50 20 10
Sandpoint 40 61 42 49 33 47 / 70 20 100 70 30 20
Kellogg 41 60 40 46 34 43 / 60 20 100 50 40 30
Moses Lake 45 61 44 58 36 54 / 80 20 50 10 10 0
Wenatchee 44 60 42 56 39 54 / 80 40 80 10 10 10
Omak 42 57 42 53 34 53 / 90 40 90 30 10 0

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...Wind Advisory from 8 PM Saturday to 3 PM PDT Sunday for lower
Garfield and Asotin counties-Spokane area-upper Columbia
Basin-Washington Palouse.

&&

$$

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