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Area forecast discussion 
National Weather Service Spokane Washington
338 PM PST Friday Feb 5 2016

Synopsis...
another frontal system will arrive tonight bringing rain to The
Lowlands and snow to the mountains. It will become windy after
midnight tonight with gusts up to 45 mph over southeast
Washington, the Palouse, and West Plains. Dry weather and light
winds will develop on Sunday and continue through mid week as a
strong high pressure system sets up over the region. More active
weather is expected by the end of the work week.

&&

Discussion...
..windy conditions tonight into Saturday morning...

Tonight and saturday: a dynamic shortwave trough of lower pressure
will race across the region tonight. Satellite imagery shows the
cold front just off the coast of Washington at around 2:00 PM this
afternoon. The water vapor channel indicates good darkening
immediately behind the front. This is a good signal that once the
precip shuts off, we will see low clouds mixing out and stronger
winds aloft mixing down. Precip will mainly be confined right
along the cold front for most areas. This will result in a short
duration precip event of between 2-4 hours. The exceptions will be
the east slopes of the northern Cascades and the Idaho Panhandle.

The slop over precip across the Cascade crest has the potential
to extend a bit further into the east slopes more than usual as
high resolution models (i.E. Hrrr) indicate a moderately strong
Puget Sound convergent zone (pscz) setting up. Snow fall amounts
in the east slopes of the northern Cascades will likely be fairly
light with the front this evening, but snowfall rates may be quite
heavy underneath the pscz through the overnight hours. The hrrr
model shows this convergent zone first extending over the Methow
Valley late in the evening through about 2:00 am and then
concentrating further south between plain and Lake Chelan late
tonight into Saturday morning. It is not uncommon to see snowfall
rates of 1-2 inches per hour underneath the pscz due to the
convective nature of the snowfall. Because of this, we have made a
minor adjustment to the Winter Weather Advisory to include plain
and locations along Lake Chelan such as Lucerne.

Snowfall amounts are not expected to be as heavy across the Idaho
Panhandle, but some ongoing snow showers are expected to continue
through Saturday morning. Some showers may be on the heavier side
behind the cold front as lapse rates steepen a bit. The main
impact will be going over Lookout Pass where around 2-4 inches of
snow will be possible.

The other impact with this storm system will be for some windy
conditions. The GFS model indicates the strongest potential for
winds. It shows winds up at 850 mbs of up around 50 kts, but other
model guidance are closer to 40-45 kts. There will be decent cold
air advection with the passage of the cold front with a degree of
confidence that these stronger winds aloft will be able to mix
down to the surface despite a nighttime passage. Strongest wind
gusts are expected to take place across the Spokane area, on the
Palouse, and in the northeast blue mtns (including around Pomeroy
and over Alpowa summit). Strongest gust will likely occur with
cold front passage late tonight into early Saturday morning in the
range of 40-45 mph. Winds will then be generally breezy for the
rest of the day on Saturday. Gust potential will be borderline
advisory criteria, but confidence is low and duration will likely
be fairly short if achieved. /Svh

Saturday night through Friday...model agreement is good and
consistent for multiple runs now in depicting a strong upper level
ridge over the region from Sunday through Wednesday. Confidence
is high for a run of dry weather after lingering snow showers from
saturday's system die out over the Idaho Panhandle. The areal
extent of at least morning fog and low clouds...potentially
deteriorating air quality and temperatures will be the main
forecast problems during this strong ridge inversion scenario.

The region may be broken out into three distinct areas of varying
weather. Firstly...over the Palouse and points south as far west
as Ritzville or so a persistent easterly gradient will likely keep
fog and low clouds to a minimum and allow temperatures to elevate
int the solid 40s and even into the 50s by mid week.

The easterly gradient will serve to pool an increasingly moist and
stagnant boundary layer in the deep basin and Cascades
valleys...banked against the mountains. It is here where the best
chance of significant fog and stratus and the lowest chance of
daytime sun will be found. Also the coolest temperatures and
weakest diurnal swings.

Over the northern Columbia Basin and many of the valleys of
northeast Washington and north Idaho a regime of overnight and
morning fog and low clouds with at least partial sunshine in the
afternoons and evenings look plausible...with the protected
valleys north of the basin slowest to scrub each day.

On or about Thursday models are coming into loose agreement on
breaking down or at least substantially weakening the upper ridge
with both the GFS and ec depicting a short wave passage either
Wednesday night or Thursday...followed by a more active close to
the work week with follow on waves. At this time none of these
disturbances looks particularly strong or organized...but well
Worth increasing precipitation chances for valley rain and
mountain snow for late in the week. /Fugazzi

&&

Aviation...
00z tafs: a strong cold front laying along the pac coast at 00z
will pass through keat around 06z and through the eastern taf
sites around 09z. Ahead and along this front expect mainly rain
showers with possible MVFR ceilings...except a short period of
snow at keat then changing to rain. Ahead of the front especially
over the eastern taf sites low level wind shear is expected after sunset decouples
the boundary layer until frontal passage. Breezy and gusty conditions will
occur with the frontal passage with precipitation quickly tapering
off...except for the Idaho Panhandle and possibly the kcoe taf
site where upslope Post-frontal showers will continue into the
morning hours. Generally decreasing winds and VFR conditions will
prevail during the day Saturday. /Mjf

&&

Preliminary point temps/pops...
Spokane 33 40 28 40 30 43 / 70 10 0 10 0 0
Coeur D'Alene 32 40 26 39 30 44 / 100 20 10 10 0 0
Pullman 36 42 30 44 33 48 / 60 10 10 10 0 0
Lewiston 40 50 32 50 35 54 / 20 10 10 10 0 0
Colville 32 39 27 36 29 41 / 80 10 0 10 0 0
Sandpoint 33 39 27 36 29 41 / 100 30 10 10 0 0
Kellogg 32 36 26 37 30 43 / 100 60 10 10 0 0
Moses Lake 32 46 29 43 31 45 / 40 0 0 10 0 0
Wenatchee 31 42 29 38 30 40 / 40 10 0 10 0 0
Omak 30 40 26 34 29 38 / 60 0 0 10 0 0

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...Winter Weather Advisory from 6 PM this evening to 8 am PST
Saturday for east slopes northern Cascades.

&&

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