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Area forecast discussion
National Weather Service Spokane Washington
245 PM PDT Tue Oct 17 2017

Synopsis...
strong winds will continue across the region this afternoon and
evening. Gusts up to 50 mph over lowland and valley locations with
gusts to 60 mph or higher over the mountains are possible through
8 PM. Unsettled weather will continue Wednesday through Friday. A
cold front late Thursday will cool the region down again to
slightly below average temps through Saturday. Mountain snow will
be possible Saturday.

&&

Discussion...

Tonight: guidance suggests the upper level jet and the trop
fold/area of darkening on water vapor just behind it pass through
eastern Washington and north Idaho quickly with the base of the
water vapor darkening east of the area in southern Alberta/southeast
British Columbia around 5 PM PDT this evening so perhaps it is being
conservative to hold onto the advisory through 8 PM PDT.
Additionally any rainfall from the passing disturbance is expected
to be extremely light with the bulk concentrated up over the
northeast Washington mountains and the northern mountains of the
north Idaho Panhandle. Regardless with the passage of this
disturbance there will be a small interval of clearing with the
decreased winds followed by more clouds invading the sky from the
west signaling the approach of yet another low pressure system. Left
some mention of late night patchy valley fog in place in northern
valleys. /Pelatti

Wednesday through Friday night: very unsettled weather is
expected for the remainder of the work week. A warm front will
spread across the region on Wednesday. Stratiform precip will
start along the Cascades in the morning and then spread east
through the afternoon. Rain will continue through the evening and
overnight hours, especially for NE Washington and north Idaho. This system has a
good moisture tap associated with it and most locations should see
light rain. The exception to this will be portions of the lc
valley and Camas Prairie where they could get nothing. Thursday
afternoon a cold front will push into the Cascades, and into north
Idaho by late evening. This front is quite a bit weaker than today's
front. By Friday the upper level trough is over the inland northwest
with instability showers everywhere except the Wenatchee area,
Waterville Plateau and portions of the western Columbia Basin.
Conditions look to start to dry out Friday night...but only for a
very brief amount of time.

Precipitation amounts: the bulk of the precipitation across the
Cascades will fall Wed into early Thursday morning. Along the
crest they could see upwards of 2 to 4 inches of rain. As you come
off the crest towards Leavenworth, plain, Winthrop...they could
see 1-1.5 inches. Places like Wenatchee and Moses Lake will see
the least amt of precip during this period...with 0.10 to 0.20
possible. Spokane, the Palouse couer d'alene area will see about a
half to three quarters of an inch from Wed-Fri. NE Washington and north Idaho
which includes Stevens, Pend Oreille, boundary and Bonner counties
will see in the valleys 0.80 to over an inch...locally up to an
inch and half in Idaho around Bonners Ferry. The mountains around
there could see 1 to 3 inches of rain...with the higher amounts in
Idaho. Last but not least southeast Washington into the lc valley and Camas Prairie
while will not get much if any precip on Wednesday, will see rain
on Thursday evening into Friday morning with the cold front
passage, and could see 0.25 to 0.50.

Winds: southwest winds will increase Wednesday afternoon and
remain elevated through Friday night. Gusts to 25 is likely for
most locations. Some locations could see gusts up to 35 mph.

Snow levels: snow levels will increase Wednesday and remain
fairly high (7-9k ft) through Thursday until the cold front
passes. Snow levels will then lower Thursday night and Friday down
to 4-5k ft. There could be some decent snow amounts in the
Cascades along the Canadian border Wed aftn as snow levels are
rising, but snow levels will be above 5k-5500 ft and is not
expected to impact any passes.

Temperatures: daytime temperatures will be slightly below average.
Lewiston will likely see at or above avg temps. Overnight lows
will be above average given the winds remaining elevated through
the nighttime hours. /Nisbet

Saturday: a powerful westerly jet will bring Rain, Mountain snow,
and more windy weather to the Pacific northwest this weekend.
There is good model agreement that a 250mb jet of 130-150kts will
be focused across Washington and north Idaho on Saturday. We are
looking for bands of moderate to locally heavy precipitation to
spread across Washington Saturday into Saturday night along a
vigorous warm front. Early morning snow levels may be as low as
3000-4000 feet in the Cascades and mountains of northeast
Washington and north Idaho. Heavy mountain accumulations will be
possible in the Cascades on Saturday. Rapidly rising snow levels
Saturday afternoon and evening should limit snow accumulations in
the Panhandle and northeast Washington, but elevations above 5000
feet will have a decent shot of several inches by Saturday
evening. For The Lowlands, saturday's storm looks to be a wet one.
October storms similar to this one often produce over a half inch
of rain over the Panhandle and the mountainous zones of northeast
Washington. The exact track of the surface low will be a
determining factor in precipitation amounts with this fast moving
system. Storm track and timing will also dictate how much wind we
receive. At this time, it looks like 40 to 50 mph wind gusts will
be a possibility Saturday evening with mountain ridges potentially
gusting higher.

Sunday: by Sunday, the medium range models are forecasting the jet
axis to begin lifting north of the Canadian border. The GFS
suggests a secondary shortwave passage on Sunday leading to
chances for showers. The European model (ecmwf) is drier, but maintains showers
over the Cascades and Idaho Panhandle mountains.

Monday and tuesday: at this time, it looks like Monday and Tuesday
will be relatively quiet as upper level high pressure returns to
the western US. Our forecast for early next week is calling for mild
afternoon temperatures and chilly nights. /Gkoch

&&

Aviation...

..strong winds today...

12z tafs: cold front passage to bring strong winds to the aviation
area today. A few locations in the Lee of the Cascades as well as
parts of the Columbia Basin have not had the stronger southwest
winds totally mix down to the surface and as such there is some
mention of low level wind shear until 19z as after that time it is
expected that the upper level winds should mix down to the
surface. Wind gusts of 30 to 45 mph to prevail with some isolated
gusts between 50 and 60 mph between 22-00z, otherwise the typical
nuisance expected with the windy conditions would be blowing dust
and haze. Winds expected to decrease substantially in the early
evening after 03z Wednesday and brief clearing. More clouds invade
sky after 06z Wednesday and on through tonight into early
Wednesday morning signaling the approach of yet another low
pressure system expected to bring rain to the aviation area
Wednesday afternoon after 18z Wednesday. /Pelatti

&&

Preliminary point temps/pops...
Spokane 41 54 48 53 42 50 / 0 80 80 90 60 50
Coeur D'Alene 39 55 46 56 41 49 / 0 70 80 90 80 50
Pullman 43 59 49 58 43 50 / 10 40 30 60 80 40
Lewiston 46 67 49 66 47 58 / 0 20 10 10 80 20
Colville 35 53 44 54 41 52 / 0 90 70 80 70 40
Sandpoint 34 52 43 52 38 48 / 0 100 100 100 100 70
Kellogg 38 53 42 56 40 45 / 20 50 60 50 90 80
Moses Lake 37 60 47 60 38 57 / 0 60 50 50 30 10
Wenatchee 39 58 45 59 41 55 / 0 40 20 50 40 10
Omak 34 56 40 59 36 56 / 0 70 70 70 30 20

&&

Otx watches/warnings/advisories...
Idaho...Wind Advisory until 8 PM PDT this evening for central Panhandle
mountains-northern Panhandle.

Wind Advisory until 8 PM PDT this evening for Coeur D'Alene area-
Idaho Palouse.

Washington...Wind Advisory until 8 PM PDT this evening for east slopes
northern Cascades-northeast mountains-Okanogan Highlands-
Okanogan Valley-Wenatchee area.

Wind Advisory until 8 PM PDT this evening for lower Garfield and
Asotin counties-Moses Lake area-Spokane area-upper Columbia
Basin-Washington Palouse-Waterville Plateau.

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