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Area forecast discussion 
National Weather Service Spokane Washington
431 am PST sun Feb 14 2016

Synopsis...
rain and mountain snow will spread slowly northeast into eastern
Washington and north Idaho the next 24 to 36 hours. Accumulating
snow will likely impact travel over Lookout Pass this morning on
Interstate 90 as well as Stevens Pass on Highway 2 over the
Cascades. Snow levels will rise markedly by tonight and into
Monday and temperatures will seem more like early April than mid
February. Many locations will experience highs in the 50s to low
60s on Monday and Tuesday. More wet weather will arrive for middle
to late week with occasionally windy conditions.

&&

Discussion...
today through Mon nt: we'll be letting the winter wx advsy for the
cntrl ID Panhandle mtns end in the next few hours as we transition
to an increasingly stable air mass, weakening upslope flow, and
slowly rising snow levels. However...this more stable air mass
will be characterized by widespread stratiform pcpn within a zone
of isentropic ascent over a warm frontal boundary currently
developing across srn WA. This warm front will lift north the next
24 hrs keeping a persistent moderate to heavy pcpn threat across
all of north Idaho and from the Palouse north to the British Columbia border in a
warm conveyor belt of rich moisture containing pwat values
approaching 200 percent of normal. This combination of around an
inch of rain and melting snow in the Idaho Panhandle will produce
rises on area rivers and streams. A strong, nearly unidirectional,
westerly vertical wind profile will help to produce a significant
pcpn shadow in the Lee of the Cascades by late today and keep much
of the upper Columbia Basin dry. This northward translation of the
previously mentioned front will coincide with a amplifying upper
ridge through Mon nt and put all of ern WA and north Idaho at the nose
of a thermal ridge at 850 mb by Mon, allowing for good mixing and
coupling with 40-50kt 850mb winds aloft. Though Mon will see
record breaking high temps and sun for much of ern WA, it will
also be very windy... with persistent west winds of 25 to 35 mph
from the Tri- Cities NE through the Palouse and into the Spokane
region. Gusts to 50 mph on ridge tops is possible Mon for the nrn
blue mtns. Also, late Sunday nt and Mon will see a moderately
favorable setup for very gusty mtn winds in the Cascades as the
polar jet moves north and establishes an inversion just above the
Cascade crest that may help to enhance the ridge-top flow
dramatically. This will be monitored closely the next 24 hours as
some model guidance is showing a north to south corridor of 60 mph
winds along the east slopes of the Cascades. It appears at this
time that the Lower Valley towns such as Wenatchee will not see
these strong winds, but ridgetops and higher exposed terrain may
not be so lucky.

See our wx stories concerning all of the above impacts on
our Spokane National Weather Service web Page. Stay tuned...bz

Tuesday through saturday: an active storm track will continue
over the inland northwest through the remainder of the week. Most
active periods look to be Wednesday night through Friday with a
pair of storm systems tracking through. Each will bring a chance
of valley Rain/Mountain snow and breezy winds.

The first weather system is expected for Wednesday night through
Thursday. This system will have a better moisture tap associated
with it originating from the sub-tropics. The upper level trough
will become rather elongated as it pushes in off of the eastern
Pacific, which will prevent a more direct moisture plume
orientation that would be observed in an atmospheric river type
scenario. This will help to keep hydrology concerns to a minimal
level even though rivers and streams across the region will be on
the rise early next week. Good southerly flow ahead of the trough
will also keep snow levels high with accumulating snow expected to
mainly remain above pass levels. The caveat to this will be
behind the cold front. There is still quite a bit of uncertainty
as to the timing of cold front passage. The general consensus is
that frontal passage will be Wednesday night. Snow levels will
drop during this time with rain possibly changing over to snow
showers over Stevens Pass. Winds are likely to be breezy on
Thursday, but current model guidance does not show much cause for
concern they don't look to be strong enough to meet advisory
criteria.

A short break in the weather is expected Thursday evening/night
before the next shortwave disturbance arrives. This system also
looks fairly progressive. Snow levels will start out lower with
this next wave, so there will be a better chance for accumulating
snow above 3000 feet. The current timing of this system is not
favorable for accumulating snow on the passes as much of the
moisture looks to fall Friday morning/afternoon. The front will
deliver another round of breezy winds to the region from Friday
afternoon into the evening. As with the previous storm system,
this also does not look particularly strong, so borderline
advisory type wind speeds are possible but most likely will be a
low impact event.

Temperatures will see a cooling trend through the week, but will
still remain mild and above seasonal averages. /Svh

&&

Aviation...
12z tafs: expect another round of rain with VFR/MVFR cigs today
and tonight as a frontal boundary lifts north across the region. A
strong mid- level westerly wind has produced a rain shadow east of
the Cascades limiting rain amount for Wenatchee, Moses Lake, and
Omak. The near sfc air mass should be moist enough to produce fog
in Wenatchee. Spokane, Coeur D'Alene, and Pullman will see light
rain slowly move north, with ceilings on average lowering to at
least MVFR through Mon 12z.

&&

Preliminary point temps/pops...
Spokane 47 42 54 46 53 42 / 80 30 20 10 10 30
Coeur D'Alene 46 41 53 45 52 41 / 80 70 60 20 30 30
Pullman 50 44 56 46 55 44 / 90 70 30 10 20 20
Lewiston 55 46 63 47 61 45 / 90 60 20 0 10 10
Colville 42 37 51 41 50 39 / 60 30 40 30 10 30
Sandpoint 41 37 49 40 47 38 / 70 80 80 60 60 40
Kellogg 42 38 46 41 45 39 / 90 100 90 70 60 40
Moses Lake 51 43 60 42 57 44 / 20 0 0 0 10 10
Wenatchee 48 39 56 41 54 40 / 10 10 10 0 10 10
Omak 41 35 48 36 50 38 / 20 10 10 10 10 20

&&

Otx watches/warnings/advisories...
Idaho...Winter Weather Advisory until 10 am PST this morning for central
Panhandle mountains.

Washington...air stagnation advisory until 10 am PST Tuesday for east slopes
northern Cascades-Okanogan Valley.

&&

$$

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