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Area forecast discussion
National Weather Service Spokane Washington
242 am PDT Sat Oct 21 2017

Synopsis...
the region can expect active weather through the weekend.
Widespread rain and High Mountain snow will develop this morning
over the Cascades and spread through eastern Washington and north
Idaho through the day. Tonight and Sunday will be quite windy
with gusts of 40 to 50 mph across portions of the open wheat
country of Washington and the Idaho Palouse. Mild weather will
return Monday and Tuesday before more wind and precipitation
returns Wednesday.

&&

Discussion...

..snow to impact portions of the area today...

..Gusty winds tonight and Sunday for southeast Washington and
portions of Idaho...

Today through Sunday night...the active pattern will continue through
the weekend, then we get a break finally early next week. The
next Pacific storm system is barreling into the West Coast this
morning. The combination of a strong warm front and a short wave
disturbance will provide more then enough lift to squeeze out the
abundant moisture associated with this disturbance. So widespread
rain and snow is expected today and this evening. A cold front
will follow tonight to bring drying from the northwest. Showers
will linger in the orographically favored area such as the Cascade
crest and the Panhandle mountains through Sunday. With air mass
changes like this we will also have windy conditions across the
region.

* Precipitation: yes and plenty of it again with this storm
system. The Cascade rain shadow will not be a prevalent this
time around so even these areas will get plenty of moisture.
Through Sunday afternoon the lower east slopes of the Cascades
and the deep basin will see amounts from three tenths to around
a half inch, the remaining lower elevations from a half inch to
around three quarters of an inch, and the mountains 1-3 inches
of precipitation. The Cascades could see 2-4 inches.

* Snow: snow levels are expected to start out around 3000-3500
feet across the south, 2500-3000 feet for the northeast
mountains and around 2000 feet or less for the Cascades this
morning, before increasing through the day. This will result in
several hours of moderate to heavy snow for the Cascades an the
Okanogan Highlands. Currently the Methow valleys is cold enough
to support several inches of snow as well. As such a Winter
Weather Advisory has been hoisted for these areas today. Some of
the northern valleys may see some wet accumulations this
morning too, there is even a possibility of a rain/snow mix
around Spokane and Pullman this morning.

* Winds: model guidance indicates a 130kt jet along the Canadian
border Saturday night and Sunday. The gradient tightens up
significantly and 850 mb winds increase to 50-60 kts. Guidance
is showing the best gusts tonight into Sunday morning and a Wind
Advisory for the eastern basin the PA louse, lower Garfield
County and the Spokane-Coeur D'Alene area will be put out to
cover this. Winds gusts in these areas will be similar to the
recent event we had earlier in the week. Tobin




Monday and tuesday: models continue to show an upper ridge
building over the area for a warming trend and dry weather with
light winds.

Wednesday: models continue to show a cold front dropping down from
the northwest. Still some differences with the strength of the
front. The European model (ecmwf) is the strongest with sharp height falls in the
afternoon and an intensifying surface low to 989mb over southern
Alberta...the GFS is close to the European model (ecmwf) but not quite as strong
while the Canadian is much different...showing just a weak
frontal passage. With the European model (ecmwf) the most consistent solution and
the GFS trending this way the forecast leans towards a strong cold
front. Prefrontal 850mb winds increase to 40-50 kts and given a
daytime front passage the potential exists for these gusts to mix
down to the surface with the Palouse, upper Columbia Basin, and
Pomeroy areas most favored. The mountains will be windy as well.
Behind the front windy conditions will develop down the Okanogan
Valley channeling down towards the Waterville Plateau and Ephrata
areas during the afternoon and evening. Regarding
precipitation...models continue to show about a six hour period of
showers along the Cascade crest and Idaho Panhandle with the
front passage...with a chance of showers over the eastern third of
Washington while much of central Washington remains dry due to
strong downslope flow off the Cascades. Snow levels are expected
to remain above pass levels during most of this short burst of
precipitation.

Thursday and friday: cooler and drier air moves in behind the
Wednesday cold front passage. Given model differences with the
strength of the front and the amount of cold air advection...there
are large model differences Thursday and Friday regarding
temperatures. Thus did not make many changes given the
uncertainty. Jw

&&

Aviation...

06z tafs: the next system will move into the region Saturday
morning, spreading rain and mountain snow over the area. Cigs will
be around the MVFR/IFR threshold for much of the day in most
locations. The southeasterly winds should mean lower cigs for eat,
but not as low for the eastern tafs. But when the wind shifts to
southwesterly on Saturday evening, the opposite will be true. Cigs
should improve at eat, but lower for geg/sff/Coe/puw. Rj





&&

Preliminary point temps/pops...
Spokane 46 45 60 40 56 39 / 100 100 20 0 0 0
Coeur D'Alene 45 41 59 40 55 38 / 100 100 40 10 0 0
Pullman 47 45 60 43 58 41 / 100 100 80 10 0 0
Lewiston 53 49 65 45 62 43 / 100 90 50 10 0 0
Colville 44 39 60 35 57 35 / 100 100 10 0 0 0
Sandpoint 44 38 55 34 53 33 / 90 100 80 10 0 0
Kellogg 42 39 52 38 52 38 / 90 100 100 20 10 0
Moses Lake 50 48 65 38 61 35 / 100 80 10 0 0 0
Wenatchee 47 41 62 40 59 40 / 100 90 10 10 0 0
Omak 47 38 60 34 55 33 / 100 100 10 10 0 0

&&

Otx watches/warnings/advisories...
Idaho...Wind Advisory from 9 PM this evening to 1 PM PDT Sunday for
Coeur D'Alene area-Idaho Palouse.

Washington...Winter Weather Advisory from 5 am early this morning to 7 PM PDT
this evening above 3500 feet for east slopes northern
Cascades.

Wind Advisory from 9 PM this evening to 1 PM PDT Sunday for
lower Garfield and Asotin counties-Spokane area-upper
Columbia Basin-Washington Palouse.

Winter Weather Advisory from 5 am early this morning to 7 PM PDT
this evening for Okanogan Highlands.

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