Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Spokane Washington
1140 am PST Monday Mar 2 2015

Synopsis...
a weak weather system will pass through the region today with the
potential for light snow mainly for the Idaho Panhandle, along
with breezy conditions across much of the region this afternoon and
tonight. Much colder air moves in behind this system, with
temperatures well below average for the middle of the week. A dry
period, with moderating temperature will follow for the end of the
week.



&&

Discussion...
morning update: we continue to track a shortwave dropping south
across western Canada, working into northeast Washington and north Idaho.
This feature will result in a couple things: snow showers and
breezy conditions.

Thus far much of Cascades, south and eastern Washington and north Idaho are
mostly cloudy to cloudy. Some light flurries are falling from
these clouds. I except some isolated snow showers are falling in
this as well, especially over the higher terrain. However I am not
seeing much in the way of measurable precipitation or any sign of
it on area webcams. However things should change going into this
afternoon.

Most of the short-range models take the incoming shortwave and
some unstable lapse rates associated to Blossom scattered to
locally numerous snow showers through the afternoon, especially
starting somewhere toward the 1 to 3 PM. I'm tracking the edge of
that shortwave on WV satellite, coming toward southeast British Columbia
near Blue River. Models track it south-southeast into northeast
Washington/north Idaho later this afternoon, along with steepening lapse
rates. This should be the impetus for the increasing showers. And
given the atmospheric thermal profile, this should fall mostly as
snow.

In these kind of convective situations it is very, very difficult
to pin-down snow accumulations, especially away from the mountains.
On average amounts could range from a trace to two-tenths of an
inch in the valleys, but the heavier convective or more persistent
bands could produce local amounts to an inch or so. Then the
other question is how effectively that would accumulate, again
outside of the mountains, given things like ground temperature and
air temperature which are expected to be above freezing. So watch
for some heavier bands and perhaps some accumulation, but better
confidence for snow actually sticking more effectively would be in
the mountains above about 2500-3500 feet. About 2 to 4 inches is
possible there.

Lastly winds will be on the rise. They are already increasing
down the Okanogan Valley and are expected to increase elsewhere
later this afternoon and evening. However winds may wait to
increase away from the Okanogan Valley until that shortwave gets
into the region, which could be around 3 to 7 PM.

I made updates to tweak pops for the day and evening, then dry
things out over much of the region overnight, save for perhaps
around the northern mountains and central Panhandle to Camas
Prairie.

Temperatures are tricky, but I did lower them some across the east
and raise them or leave them the same toward the Lee of the
Cascades. /J. Cote'



&&

Aviation...
18z tafs: incoming shortwave will increase snow showers this
afternoon, around the geg to Coe to puw/lws area. Some locally
heavier bands of snow are possible in the convective pattern and
incoming vort Max. Primarily VFR conditions are expected, but
local MVFR conditions are possible in the heavier bands. The
snow shower threat and clouds will dissipate after 03 to 07z.
Western taf sites are expected to see little other than flurries.
Winds will be on the increase through the afternoon and values
remain breezy through the evening, before abating overnight.
/J. Cote'



&&

Preliminary point temps/pops...
Spokane 41 19 34 17 42 23 / 40 30 10 0 0 0
Coeur D'Alene 39 17 35 14 43 20 / 60 50 10 0 0 0
Pullman 43 21 35 17 43 25 / 40 30 10 0 0 0
Lewiston 46 26 39 20 47 26 / 20 20 10 0 0 0
Colville 43 22 39 16 45 21 / 50 40 10 0 0 0
Sandpoint 37 16 33 12 40 20 / 60 40 10 0 0 0
Kellogg 37 17 31 13 40 21 / 80 70 10 0 0 0
Moses Lake 50 24 43 20 47 25 / 0 0 0 0 0 0
Wenatchee 51 27 44 20 49 27 / 10 0 0 0 0 0
Omak 49 22 44 19 48 23 / 0 0 0 0 0 0

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&

$$

National Weather Service Glossary of Abbreviations