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Area forecast discussion 
National Weather Service Spokane Washington
449 PM PDT Monday Sep 1 2014

Synopsis...

The arrival of a cold front Tuesday afternoon and evening will
bring a return of gusty winds and cooler temperatures for Wednesday,
along with good threat of showers and thunderstorms. A warming and
drying trend is expected Thursday into next weekend.

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Discussion...

Tonight and tuesday: northwest flow will prevail across the inland
northwest for the next 24 hours, but a strong 100 kt jet in the
flow will push a fast moving cold front through the region late
Tuesday. For tonight, expect light winds, mild temperatures and
the cumulus to dissipate to mostly clear skies. For Tuesday, winds
will start off light as clouds increase from the west. The cold
front will sweep through the Cascades by Tuesday afternoon. This
will tighten pressure gradients and northwest winds will becoming
breezy. There is a chance of showers mainly near the Cascade crest
and in the far northern mountains into the evening hours. Increased
instability will be found along the front and could see a slight
chance of thunderstorms across the northern mountains as well.
/Rfox.

Tues nt through Wed nt: the entire time frame will be focused on
a deep upper trough that will quickly move southeast out of British Columbia and into
ern WA and north ID while it fills/weaken/shears before moving into
wrn Montana Wed. The core wx issues associated with the passage of
this trough and front will be gusty west winds, thunder/pcpn
amnts, and temperatures. Very gusty winds, especially near the
Cascades, will increase late tues as cold advection and cross-
Cascade pressure gradients strengthen. The biggest challenge for
Wed will be deciding the areal coverage of showers and/or thunder
across NE WA and the ID Panhandle. This will, of course, influence
temperatures with the increased cloud cover. As this wave fills,
it also develops a trowal structure Wed on the NE periphery of the
upper low that could significantly influence the amnt of pcpn that
nrn WA and north ID receives. As a result of this trowal feature,
banded pcpn could certainly be a problem across ern WA and north ID
Wed before the low moves east out of the area. Due to the
convective character of the wave, the deep cyclonic convergence
and trowal banding, significant pcpn amnts are possible. Storm
total rainfall amnts are fcst to be roughly three to six tenths
for the north Idaho Panhandle and NE WA by Wed nt. Cool high temps Wed
in the 60s where the heaviest rains fall looks increasing likely
as well. Bz

Thursday to monday: mostly dry, warm conditions expected before
the next rain threat arrives early next week. A trough of low
pressure exits to the east and a ridge builds in through Saturday.
With regional pwats dropping below 0.50 inches and broad-scale
subsidence, this will support dry and mostly clear conditions.
Mean 850mb temperatures warm 4 to 7 degrees by the end of the
week, supporting a warming trend that pushes highs from the mid-
70s Thursday to the lower 80s by Saturday. Saturday night through
Monday the next trough pushes in from the west-northwest. However
models continue to vary over the evolution, especially timing.
Look for some increase in cloud cover going into early next week.
A chance of showers returns to the Cascades Sunday and expands
toward northeast Washington and north Idaho Monday. This may include areas as
far south Douglas County to Kootenai County. However there is too
much model disagreement to have high confidence. The incoming
trough is forecast to bring cooler temperatures by Monday.
/J.Cote'



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Aviation...
00z tafs: expect VFR conditions across the region through 00z
Wednesday with flat cumulus dissipating this evening. For Tuesday
afternoon...a deep upper trough will be approaching with a chance
of showers in the Cascades and northern mountains in the
afternoon. The taf sites will remain dry...but with gusty
west-southwest afternoon winds with the approaching system. Jw

&&

Preliminary point temps/pops...
Spokane 52 75 50 68 46 75 / 0 10 50 30 20 0
Coeur D'Alene 50 76 50 67 42 75 / 0 10 60 40 20 0
Pullman 48 77 45 70 40 76 / 0 0 10 20 10 10
Lewiston 58 84 53 74 49 80 / 0 0 0 10 10 10
Colville 47 78 48 70 38 78 / 0 10 50 30 20 10
Sandpoint 46 74 45 64 39 73 / 0 10 70 70 40 10
Kellogg 47 71 47 65 39 71 / 0 10 50 50 50 10
Moses Lake 57 82 51 76 47 80 / 0 0 10 0 0 0
Wenatchee 59 80 54 75 52 79 / 0 10 10 0 0 0
Omak 54 80 52 73 43 80 / 0 20 30 20 10 0

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