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Area forecast discussion 
National Weather Service Spokane Washington
432 am PST Monday Nov 24 2014

Synopsis...
the weather today will be relatively chilly and quiet prior to the
arrival of a wet storm system tonight. Rain and mountain snow is
expected to develop this evening. Tonight, Tuesday and Tuesday
night will be rainy with the Idaho Panhandle and the Cascades
receiving a couple inches of rain by Wednesday. A breezy and wet
but warm Thanksgiving day will give way to a colder weather
pattern for the Holiday weekend with the mountains receiving
several rounds of snow. Snow levels will fall to valley floors by
the weekend.

&&

Discussion...
today: for today, our attention will be on the potential for fog
development this morning. Satellite and web cameras show areas of
thick fog in the valleys north of Spokane around Colville, Priest
Lake, Cusick, and Lincoln. Winds have diminished overnight over
the West Plains, Spokane area, and Coeur D'Alene. There is a good
chance of fog development around sunrise in these locations. By
this afternoon, a low pressure system making landfall in southern
British Columbia will spread warm frontal precipitation into the
northern Cascades and the mountains along the Canadian border.
Precipitation will be in the form of snow this afternoon in these
areas.

Tonight through tuesday: precipitation is expected to Blossom
quickly this evening over the Idaho Panhandle and eastern third of
Washington. Strong low level warm advection will likely lead to
precipitation falling in the form of rain or rain/snow mix in
Spokane, Coeur D'Alene and Pullman with no accumulation. The
valleys north of the Metro will be a tough call as snow levels
will be rising through the night. At this time it looks like
Sandpoint, Bonners Ferry, Priest Lake, and Metaline Falls will
have a good shot at receiving 1 to 3 inches of wet accumulation
before snow transitions to rain on early Tuesday morning. At this
time, much of the Silver Valley looks to be too warm for
accumulating snow. A Winter Storm Watch will be issued for the
mountains of far north Idaho and northeast Washington above 4000
feet. Snow levels will make or break this event. It is possible
that warm advection could push snow levels high enough that all
but the highest peaks transition to rain Tuesday and Tuesday
night.

Of additional concern will be the rain amounts anticipated over
the Palouse, Shoshone County and the headwaters of the Stehekin
River. Thirty-six hour rainfall totals from the NAM and GFS
suggest 1 to 2 inches of precipitation, mostly in the form of rain
over the headwaters of the Palouse river. The combination of
rainfall and melting snow Tuesday into Wednesday raises our
concern for the creeks ad streams feeding the Palouse river
including Paradise creek at Moscow. High snow levels over the
Cascades and two-day rain totals in the 2 to 3 inch range over the
crest will also raise our concerns for the Stehekin River and some
of the tributaries feeding the Wenatchee river. We will be
coordinating the forecasts with the river forecast center this
morning to assess the potential for river statement or watches.
/Gkoch

Wednesday through Friday night: narrow elongated ridging off the
coast and the jet stream draped across it and just to the north in
Canada along with no cold air in valleys and lowlands to overrun
is how this interval of time should start off. Any disturbances
that ride along the periphery of the ridge are expected to remain
fairly close to the northern British Columbia border but have some
potential to penetrate further to the southeast over north Idaho
as the flow becomes more from the northwest there. By Thursday
there is more digging into west side of the ridge off the coast
which allows this pattern to remain in place through Wednesday
night. At about Thanksgiving and beyond there is more uncertainty
due to the complexity of the meteorological setup with the
expectation that the jet stream may be directly overhead parts of
eastern Washington and north Idaho aligned southwest to northeast.
This is due to the earlier mentioned digging, deepening, and
intensification of the cold trof off the coast which deamplifies
the earlier mentioned narrow elongated ridge off the coast. The
overall effect is to allow any moisture streaming through the
baroclinicity of the offshore trof and over the top of the the
remaining weak ridging in the area to sag southeast and pass over
eastern Washington and north Idaho Thanksgiving day and night so
pops remain high with gusty brisk winds and snow levels that are
high enough to with valley rain and mountain snow wording...indeed
higher mountains will get snow and accumulate but the Lodge level
elevations from about 4000 ft mean sea level and below will see mostly rain.
This moisture stream continues slow sag into Friday night but
current models are slower with this progression and not bringing
in the cold air from the north down as fast. This is an important
change so I adjusted the forecast for Friday and Friday night by
warming the temperatures and raising the snow levels and held off
on the shift to northerly winds until much later Friday night.
/Pelatti

Saturday through monday: the zonal flow pattern will slowly
transition to a southern flow as a low approaches the Oregon
coast and bring moist and warm air into the region. With the
temperatures expected to be near freezing this is expected to
bring snow to the mountains of the region and rain/snow mix to
the basin and lower elevations. With more model runs, the type of
precip will become clearer. Returning travel from the Holiday
could be impacted especially in the mountain passes. Temperatures
will range from the mid 30s to low 20s during this period. /Jdc

&&

Aviation...
12z tafs: low stratus of fog will be a good bet at Spokane and
Coeur D'Alene around sunrise. The satellite fog channel shows the
valleys north of the city filled with fog and a bit of low clouds
or fog south of town. Light south winds should push this low
stratus south of kgeg, ksff and kcoe into these terminals. It is
tough to tell if this ragged low cloud is hugging the ground of a
few hundred feet above ground level. Some amendments will be
likely this morning. The NAM and GFS forecast the development of
precipitation between 0z-06z with rain the predominant
precipitation type at Spokane, Coeur D'Alene, Pullman and
Lewiston. It looks like snow for Sandpoint and Bonners Ferry.
/Gkoch

&&

Preliminary point temps/pops...
Spokane 38 35 40 38 47 33 / 10 60 70 60 50 30
Coeur D'Alene 38 35 40 37 45 32 / 10 90 90 70 60 40
Pullman 42 38 48 45 50 35 / 10 70 80 60 30 30
Lewiston 49 40 52 46 54 38 / 10 70 80 30 20 20
Colville 37 32 39 34 42 28 / 20 70 70 70 50 40
Sandpoint 35 33 38 34 41 28 / 30 100 90 80 80 60
Kellogg 36 33 38 37 40 32 / 10 100 100 100 70 60
Moses Lake 41 35 46 40 52 34 / 0 10 20 10 20 10
Wenatchee 43 36 45 40 49 33 / 10 10 20 20 30 20
Omak 34 32 38 35 43 30 / 10 20 60 60 50 20

&&

Otx watches/warnings/advisories...
Idaho...Winter Storm Watch from this evening through Tuesday evening for
northern Panhandle.

Washington...Winter Storm Watch from this evening through Tuesday evening for
northeast mountains.

&&

$$

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