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Area forecast discussion 
National Weather Service Spokane Washington
235 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...
for today and this evening...satellite imagery is matching up
with model guidance showing a vigorous upper level low dropping
south along the Oregon coast this morning. Some wrap around
moisture should make it east of the Cascades this morning to
support some light snow near the north Cascade crest. Snow
accumulations will be very light.

Satellite imagery is also showing the second advertised low
dropping south through Alberta and will give our eastern zones a
glancing blow from late this morning through this evening. Snow
showers should be confined to east of a line from about Colville
to Walla Walla...with the focus over the Panhandle mountains.
Plenty of dynamical lift to work with, but this disturbance is
lacking in any deep moisture. As such while pops are fairly high
through the afternoon and early evening, precipitation amounts are
on the lighter side. Precipitation will be as snow down to the
valley floor. Amounts will vary from a trace to a couple of
hundredths for the lower elevations around Colville...Deer
Park...Spokane Metro and Pullman. Around an inch for the northeast
mountains of Washington. The north and central Panhandle mountains
may see anywhere from 2-6 inches.

The northerly flow will result in much cooler air moving into
the region down north-south valleys. The cold air advection
combined with a tightening of the surface pressure gradient, and
30-35kt 850mb winds will increase the winds down the Okanogan
Valley and spilling into the Waterville Plateau and the Columbia
Basin. The Purcell Trench is somewhat protected form this flow but
should still see increase north-northeast winds later this
afternoon and early this evening. Winds will increase by mid day
with sustained winds of 20-30 mph with gusts 30-35 mph through the
afternoon, before decreasing an hour or two after sunset. For the
Purcell Trench and spilling into the Spokane-Coeur D'Alene
corridor and into the Palouse north-northeast winds around 20 mph
with gusts 25-30 mph will be possible. This will result in a very
brisk/raw afternoon for the forecast area.

Tonight through Tuesday night...the upper level low will push east
and high pressure will build out around 130-135w. This will put
the forecast area in a dry northwest to northerly flow. Dry air
will push into the region for a drying trend. Some mid level
clouds will linger over the Panhandle mountains, otherwise mostly
sunny conditions. Temperatures will cool considerably. Once the
winds die down this evening and with clearing skies there should
be ample radiational cooling. Minimum temperatures will drop into
the low teens to low 20s both Tuesday and Wednesday morning...with
a few single digits possible for some of our frost-pockets. Max
temperatures will struggle to rise only into the mid 30s to lower
40s. Which is will be 8-10 degrees below normal. Tobin

Wednesday through Thursday night...a weak impulse will track
across the region Wednesday but will likely result in just some
mid to high clouds. Northerly flow will keep temperatures below
seasonal normals for one more day before starting a slow climb to
more seasonal levels as the ridge axis moves toward the coast.
Cold northerly flow will be replaced by a northwest trajectory
that will bring more of a marine influence to the air mass. This
will allow temperatures to start the warming trend with an
increase of about 5 to 7 degrees expected Thursday and again
Thursday night.

Friday through Sunday...medium range models continue to be at odds
concerning a shortwave trough affecting the area Friday into
Friday night. The latest European model (ecmwf) guidance continues to bring this
feature southeast across much of the forecast area while the GFS
remains firm in keeping it well to our northeast. No changes made
to this portion of the forecast until models settle on a solution.
For now, low end pops will remain over the higher terrain.
Temperatures will moderate as the synoptic flow shifts from
northerly to more westerly. /Kelch

&&

Aviation...
06z tafs: VFR conditions to prevail at most taf sites. High
clouds continue to invade and thicken above in association with
incoming front. Little in way of prolonged and intense
precipitation expected with it so brief MVFR ceilings and
visibilities may be associated with any snow showers which occur.
In the wake of this front the northeast wind will increase in
intensity and be quite gusty from about 5z Tuesday into the
evening. /Pelatti



&&

Preliminary point temps/pops...
Spokane 42 19 34 17 42 23 / 30 10 10 0 0 0
Coeur D'Alene 42 17 35 14 43 20 / 50 20 10 0 0 0
Pullman 42 21 35 17 43 25 / 40 20 10 0 0 0
Lewiston 46 26 39 20 47 26 / 20 20 10 0 0 0
Colville 45 22 39 16 45 21 / 50 10 10 0 0 0
Sandpoint 39 16 33 12 40 20 / 60 30 10 0 0 0
Kellogg 38 17 31 13 40 21 / 80 60 10 0 0 0
Moses Lake 50 24 43 20 47 25 / 10 0 0 0 0 0
Wenatchee 51 27 44 20 49 27 / 10 0 0 0 0 0
Omak 47 22 44 19 48 23 / 10 0 0 0 0 0

&&

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

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