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Area forecast discussion 
National Weather Service Spokane Washington
234 PM PDT Sat Apr 18 2015

Synopsis...
a mild and dry weather pattern is expected through Tuesday. Above
average temperatures are expected with temperatures more than ten
degrees above average the next several days. The arrival of a cold
front on Wednesday will bring the threat for showers and cooler
temperatures.

&&

Discussion...

Tonight through tuesday: the remainder of the weekend into early
next week will feature a strong high pressure ridge over the
western United States. There will be essentially no chance for
precipitation until the axis of the 500mb ridge shifts toward
Montana Tuesday afternoon. Our resident air mass is quite dry. As
of 2 PM, our afternoon humidity levels were in the teens and low
20s following the passage of a dry cold front last night.
Dewpoints will modify a bit Sunday and Monday, but the resident
air mass won't moisten significantly until air of marine origins
arrives Tuesday evening. The first opportunity of showers looks to
be Tuesday afternoon and evening over the Cascades. Both the NAM
and GFS produce surface based instability along the Cascade crest.
At this time, the models produce enough instability to mention a
small chance for thunderstorms in the Cascades Tuesday
afternoon/evening. This evening through Tuesday, look for
relatively light winds and above average temperatues. /Gkoch

Tuesday night through Saturday...for the extended forecast models
show a series of short wave troughs passing through the area from
the west or southwest. This will result in periods of showery
weather and increased cloud cover but also opportunity for dry
weather in between. Models continue to struggle with the
timing...strength...and track of individual features resulting in
lower confidence with the details. This pattern will favor a
gradual cooling trend through the week...with low confidence with
precise values due to the uncertainty with the timing of
individual rounds of clouds/showers. Snow levels look to remain
generally above pass levels due to the prevailing southwest flow.
Jw

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Aviation...
18z tafs: mostly clear skies and good visibilities will prevail at
the airports in eastern Washington and north Idaho today and
tomorrow. Strong upper level high pressure will be the predominant
weather feature the next couple of days. A northerly pressure
gradient will persist through the afternoon and weaken this
evening leading to light and variable winds overnight. /Gkoch

&&

Preliminary point temps/pops...
Spokane 40 67 43 70 45 73 / 0 0 0 0 0 0
Coeur D'Alene 37 67 38 70 41 73 / 0 0 0 0 0 0
Pullman 38 66 40 69 41 72 / 0 0 0 0 0 0
Lewiston 42 71 44 74 47 76 / 0 0 0 0 0 0
Colville 37 72 40 74 41 76 / 0 0 0 0 0 0
Sandpoint 34 64 35 68 36 71 / 0 0 0 0 0 0
Kellogg 36 66 37 69 41 72 / 0 0 0 0 0 0
Moses Lake 39 73 41 76 43 79 / 0 0 0 0 0 0
Wenatchee 46 73 48 76 52 77 / 0 0 0 0 0 10
Omak 40 72 41 75 43 76 / 0 0 0 0 0 10

&&

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

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