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Area forecast discussion 
National Weather Service Spokane Washington
1155 am PDT Thursday Aug 21 2014

Synopsis...
today will be another active day with afternoon and evening
thunderstorms over the Cascades, northeast Washington and far
north Idaho. Friday has the potential to be even wetter for the
inland northwest with good chances for thunderstorms region-wide,
including the Columbia Basin and Palouse. Locally heavy rain and
frequent lightning will accompany thunderstorms today and
tomorrow. The threat for widely scattered showers and
thunderstorms will continue into the weekend, followed by a warmer
and drier pattern early next week.



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Discussion...

..flash flooding and debris flows possible over Cascade burn
scars today into Friday...

The Flash Flood Watch for Chelan and western Okanogan counties has
been extended to include the potential for excessive rain
beginning as early as this afternoon. The latest satellite trends
and model solutions suggest that deep convection will be possible
earlier than we though yesterday. The morning runs of the NAM and
GFS actually suggest that this afternoon and this evening may now
carry a higher potential for locally heavy rain than Friday, with
higher amounts of surface based cape this afternoon/evening. The
quicker arrival of the upper low today also puts the north
Cascades in a favorable area of upper level diffluence suggesting
the potential for back-building or storms anchoring over terrain.
Fresh burn scars like Little Bridge creek, Carlton/Cougar, Upper
Falls, Lone Mountain, and Duncan will be monitored closely. /Gkoch

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Aviation...
12z tafs: the atmosphere will become increasingly unstable this
afternoon as an upper level shortwave dives down along the coast
of British Columbia toward Washington. This system will carve an
upper low over Washington and north Idaho during the night
increasing the potential for a couple rounds of showers and
thunderstorms for much of the inland northwest. It is tough to
nail down the best window of opportunity for thunderstorms since
the upper level support for perpetuating convection will
strengthen through the night, well after our typical nocturnal
lull in convection. The tafs currently broadbrush the potential
for thunder with thunderstorms in the vicinity or vcsh for many hours, and will likely
require short-term amendments as mesoscale bands develop. /Gkoch

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Preliminary point temps/pops...
Spokane 77 55 74 52 76 54 / 20 30 40 30 10 10
Coeur D'Alene 76 53 71 52 74 53 / 40 40 50 30 10 10
Pullman 77 51 75 50 74 49 / 10 20 20 40 20 20
Lewiston 84 57 79 57 80 56 / 10 10 20 40 30 20
Colville 78 51 77 50 79 49 / 70 60 60 30 10 10
Sandpoint 71 49 68 49 74 46 / 60 60 70 30 10 10
Kellogg 70 50 65 49 70 47 / 40 30 70 50 40 20
Moses Lake 85 57 82 55 82 56 / 10 20 30 30 10 0
Wenatchee 83 58 80 59 83 58 / 10 20 50 30 10 10
Omak 83 56 79 55 83 55 / 30 60 50 30 10 10

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Otx watches/warnings/advisories...
Idaho...none.
Washington...Flash Flood Watch through Friday evening for east slopes
northern Cascades-Okanogan Valley-Wenatchee area.

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