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fxus66 kotx 171050 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
250 am PST Fri Nov 17 2017

Synopsis...
today will be breezy with snow showers over the Idaho Panhandle.
Winds will subside tonight, and Saturday will be a mild day with
light winds and near average temperatures. Precipitation chances
will increase Sunday afternoon into Sunday night. Moderate to
heavy mountain snow is expected Sunday night over the Cascades and
Idaho Panhandle mountains. A mild and wet storm system Tuesday
into Wednesday will bring another round of rain to our region.

&&

Discussion...

Today and tonight: the axis of a cold 500mb trough will pass over
eastern Washington and north Idaho this morning. Mid-level
westerly winds and steep lapse rates will accompany the trough
passage...a recipe for good upslope snow showers for the Idaho
Panhandle. By mid to late afternoon, the upper level cold pool
will move into Montana and southern Idaho leading to a decrease in
the snow showers over the mountains of Bonner and boundary
counties in north Idaho. Light snow showers will likely linger
over the high terrain of southern Shoshone County through the
night. We have seen some brief lowland accumulations on web
cameras around Kellogg, Deary, Clarkia, and Wallace, but with
temperatures in the low to mid 30s snow has melted shortly after
falling. For the remainder of the morning, winter driving
conditions will likely be limited to elevations above 4000
feet...namely Lookout Pass on I-90 where an additional 2 to 3
inches will be possible by mid to late morning.

The pressure gradient between surface high pressure building over
Oregon and low pressure east of the Continental Divide will
produce gusty west winds today. Steep low level lapse rates will
allow efficient momentum Transfer to the surface. Sustained winds
of 15 to 20 mph will be common over southeast Washington and Idaho
Palouse. Gusts as high as 30 to 25 mph will be possible by mid day
at Pomeroy, LaCrosse, Pullman and Moscow. Winds don't look to be
quite as strong along and north of I-90 in Washington with
sustained 15 mph winds gusting to 25 mph for Moses Lake,
Ritzville, and Spokane during the early to mid afternoon hours.

Saturday: a flat high pressure ridge will produce mainly dry
conditions for the inland northwest on Saturday. Winds will
generally be in the 5 to 10mph range. A good day for cleaning up
leaves and catching up on the yard work before more active weather
returns late on Sunday.

Sunday: the models are in decent agreement that Sunday will start
out dry, but the arrival of a moist frontal system during the
afternoon and evening will bring our next round of precipitation.
Portions of the Methow Valley may experience snow or a rain/snow
mix Sunday afternoon and evening, but the rest of our lowland
areas should experience rain with sunday's system. With snow
levels in the 3000-4000ft range the Idaho Panhandle will likely
receive another round of moderate to heavy snow Sunday night into
Monday morning. If the precipitation forecast from the GFS and
European model (ecmwf) verify, elevations above 3000 feet around Bonners Ferry and
Sandpoint will have a good shot of 10 to 15 inches of new snow
Sunday night. The mountains of Shoshone County above 4000 feet
stand to get 6 to 10 inches by Monday morning. /Gkoch

Monday through Thanksgiving day: look for a very active and wet
pattern across the inland northwest for the upcoming week. As a trough of
low pressure settles in the eastern Pacific, a strong southwest
orientated jet will usher in mild and moist air into the region.
The brunt of the atmospheric river will bring wet weather to the
Washington/or coast, although pwats of near an inch look to span east of
the Cascades especially Tuesday night into Wednesday. The models
do struggle on the timing of the features and the onset of the
precipitation, although confidence increases by mid week as the
slow moving precipitation band sags through the region. The European model (ecmwf)
has been the more steady model, while the GFS and its ensembles
have been playing catch up. Opted to blend the two for the
extended forecast. Both show temperatures and snow levels on the
rise, peaking around Wednesday as a warm front pushes north
through the region followed by breezy southerly winds. A cold
front will bring gusty winds Wednesday night into Thursday with a
slow decrease of rain and mountain snow. Temperatures should
remain milder than normal through the end of the week. Travel for
the Holiday weekend will focus on mountain snow at the passes
early in the week, then mainly wet and breezy for mid week. Snow
should return to the pass level by week's end. /Rfox.

&&

Aviation...
06z tafs: an upper trough passage tonight will result in showers
mainly for the Idaho Panhandle and near the Cascade crest. A
moist boundary layer in the wake of the trough passage and low
level upslope flow will likely lead to another round of stratus
for kgeg/ksff/kcoe/kpuw. This stratus will begin lifting mid to
late morning with VFR conditions expected Friday afternoon and
evening. Downslope flow off the Cascades should result in a
continuation of VFR conditions for most of central Washington
including keat/kmwh. Jw



&&

Preliminary point temps/pops...
Spokane 42 31 43 30 44 35 / 10 0 0 0 20 80
Coeur D'Alene 42 31 41 29 43 35 / 20 0 10 0 20 90
Pullman 43 32 44 32 47 36 / 20 10 0 0 10 100
Lewiston 50 35 48 34 51 40 / 10 0 0 0 10 90
Colville 43 28 40 29 40 33 / 10 0 10 10 60 90
Sandpoint 40 29 38 28 40 33 / 40 10 20 0 30 100
Kellogg 38 31 38 28 41 32 / 70 20 20 0 10 100
Moses Lake 51 31 46 30 46 34 / 0 0 0 0 20 60
Wenatchee 47 33 44 32 43 33 / 0 0 0 0 20 40
Omak 43 30 42 31 40 32 / 0 0 0 10 40 60

&&

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

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