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Area forecast discussion 
National Weather Service Spokane Washington
452 am PDT Tuesday Sep 2 2014

Synopsis...
breezy winds are expected late this afternoon and early this
evening with the passage of a cold front. The front will also
bring the potential for showers and thunderstorms to the Idaho
Panhandle and northern Washington tonight into Wednesday. Thursday
morning will be cold with low temperatures down into the lower to
mid 30s for the Mountain Valley locations. The return of high
pressure Thursday through the weekend will bring several days of
dry weather, light winds, and warmer temperatures.



&&

Discussion...
today and tonight: satellite imagery early this morning shows a
potent shortwave trough of lower pressure moving south along the
British Columbia coastline. The trough axis is currently located over central British Columbia
with water vapor imagery showing a well defined dry slot at 50n
135w in the Gulf of Alaska. This dry slot is a good approximation
of the back edge of the cold front. Models have this front progged
to cross east of the Cascade mtns into the western basin after
5:00 PM this evening and then pushing into the Spokane area/Palouse
by about 8:00 PM this evening. The mountains will see the best
chances for precip with the front; however, the basin up into the
Spokane area, Coeur D'Alene area down to the Palouse and l-c
valley may only see some passing mid level clouds and possibly
some sprinkles or sporadic showers. There will be strong cold air
advection with the front, which will result in winds picking up
quite a bit along and behind the front. Strongest winds are
expected down the east slopes of the Cascade mtns out over into
the western basin for the evening hours. Sustained wind speeds of
20-25 mph with gusts up to 40 mph will be possible. This is just
below our criteria for a Wind Advisory and a highlight is not
expected at this time. The windy conditions may also result in
some blowing dust across the Moses Lake area, and could blow
across much of the basin. This may impact travel along I-90, with
the highest risk between George and Ritzville.

Behind the cold front we will see the upper level trough swing
through for the overnight hours. There is enough mid level
instability that widespread showers and even some thunderstorms
will be possible. Best areas for showers and thunderstorms will
be across the Okanogan Highlands over to the northern Panhandle.
The general progression of these showers and thunderstorms will
be to the east and southeast. This is expected to lead to at least
a chance for showers and thunderstorms across the Upper Basin to
the northern portions of the Palouse. Any thunderstorms that do
develop will be capable of drawing down stronger wind gusts aloft.

Wednesday and Wednesday night: the surface low will begin to track
away from the region across the Canadian border along the State of
Montana. With the low tracking away from the region, this will
allow surface gradients to weaken with a trend toward less windy
conditions across the region. There will be some moisture that
wraps around the low into the region, so a chance for showers and
thunderstorms will be possible into the afternoon and early
evening. Best chances for showers and thunderstorms will be in
extreme eastern Washington and in the Idaho Panhandle. Temperature will be
much cooler on Wednesday. Much of extreme eastern Washington and the Idaho
Panhandle will only warm up into the low to mid 60s with some
locations in the Panhandle having a hard time breaking 60 degrees.
Showers will dissipate overnight with skies clearing out. This
will result in temperatures plummeting overnight with the cold
pockets across the northern mountain and Panhandle valleys
dipping close to freezing. Frost will be possible, so any
sensitive vegetation should be protected for the potential of
frost or freeze damage. This will include locations such as
Republic and Deer Park. /Svh

Thursday through saturday: a split flow pattern over the Pacific
northwest will bring dry weather and light winds to the region
Thursday through Saturday. A light east to northeast pressure
gradient is expected to usher in dry surface dewpoints. The dry
air mass, light winds, and clear skies will allow for large
diurnal temperature swings. The northern valleys around Colville,
Deer Park, Priest Lake and Bonners Ferry will likely experience
low temperatures in the upper 30s and low 40s Friday and Saturday
morning with afternoon highs in the low 80s. Jacket weather in the
morning and shorts by the afternoon.

Sunday and monday: the European model (ecmwf) and GFS are in pretty good agreement
that the next shortwave trough will arrive in the Sunday/Monday
time frame. The trough will come at US from the northwest which is
a relatively dry trajectory this time of year, so the forecast for
precipitation is pretty low at this time. If the medium range
models hold true, the cold front associated with this trough will
bring a period of breezy conditions Sunday or Monday and a cooling
trend early next week. /Gkoch

&&

Aviation...
12z tafs: a strong cold front will cross east of the Cascade mtns
late this afternoon through this evening. This front will produce
gusty winds from the west and will arrive at keat and kmwh between
23-02z and then push into the kgeg, ksff, kcoe, kpuw and klws
taf sites around 03-04z. Winds will remain breezy through the
overnight hours. Showers and thunderstorms are expected across the
northern mtns late this afternoon into tonight and then begin to
push into kgeg, ksff and kcoe sometime late tonight into Wednesday
morning. /Svh

&&

Preliminary point temps/pops...
Spokane 75 50 63 46 75 49 / 10 60 40 10 0 0
Coeur D'Alene 76 50 60 42 75 44 / 10 60 50 20 0 0
Pullman 77 45 65 40 75 43 / 0 10 20 10 0 0
Lewiston 84 53 71 49 80 51 / 0 10 10 10 0 0
Colville 78 48 67 38 78 41 / 10 60 40 10 0 0
Sandpoint 74 45 58 39 73 40 / 10 70 80 20 10 0
Kellogg 71 47 56 39 71 43 / 10 50 60 30 10 0
Moses Lake 82 51 76 45 80 49 / 0 10 0 0 0 0
Wenatchee 80 56 77 52 79 54 / 10 10 0 0 0 0
Omak 80 52 74 43 80 48 / 20 40 10 10 0 0

&&

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

$$

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