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Area forecast discussion...updated 
National Weather Service Spokane Washington
518 PM PDT Thursday Jul 31 2014

Synopsis...
it will be partly cloudy and hot with isolated thunderstorms
through the end of the week and into the weekend. No significant
relief from the hot weather is forecast through the seven-day
forecast period. However, only a few spots may reach the 100-degree
mark. Isolated thunderstorms the next several days are not
expected to be strong or severe but could bring localized heavy
downpours.

&&

Update...
update this evening was to issue a Flash Flood Watch for late
Friday morning through Friday evening for the Washington Cascades.
Brief downpours from thunderstorms could produce flash flooding
across areas that have experienced recent wildfires.

&&

Previous discussion...
tonight through friday: the mid-level
ridge axis shifts east and the southwest flow begins to carry
disturbances more directly into the inland NW, increasing the
threat of thunder for some areas. Tonight one disturbance moving
across northeast or tracks by southeast Washington and the southern
Panhandle of Idaho. Interacting with the SBCAPE around The Blues and
Camas Prairie into southeast Shoshone County, this will lead to
the continued threat of some showers/T-storms largely this
evening. The threat wanes with the loss of daytime heating the
SBCAPE. However, a second and deeper disturbance was coming into
southwest or this afternoon. It is projected to move northeast
toward southern Washington overnight into Friday morning, then into Washington
during the day Friday.

First overnight into Friday morning look for some increasing
clouds. The brunt of the available instability and deeper
moisture, however, appears to remain south of our forecast area
until after about 2 or 3 am. So overnight the main shower/T-storm
chances will be over The Blues and over southwest Chelan County
Cascades. There is also concern that some activity may develop
over the lower Columbia Basin overnight and creep into the upper
Columbia Basin early Friday morning. However confidence is low and
pops will remain around 10 percent here.

Going into Friday afternoon the SBCAPE reinvigorates around the
mountain zones and secondarily toward the southeast Washington/lower Idaho.
This includes the Palouse. With the aforementioned disturbance
lifting in, this will bring a broader shower/T-storm threat about
the mountain zones and southeast Washington going into tomorrow afternoon.
General precipitation amounts are expected to be light, meaning a
concern for dry lightning and fire weather concerns. With these
factors and ongoing wildfires near the Cascades, a Fire Weather
Watch was issued for the Cascades and Okanogan Valley, Waterville
Plateau and Wenatchee area. Temperatures will remain well above
normal and relatively humidity values remain low. There could also
be an increase in winds near the Cascades with the increased
onshore flow and cross-Cascade pressure gradient. /J. Cote'

Fri nt through sunday: following the exit of the thunder-producing
short-wave trough into srn British Columbia Fri nt, Sat through Sunday will be
under the influence of a very slow moving upper trough whose pcpn
will be highly terrain and diurnally driven. Large-scale forcing
for ascent won't be very impressive with the main vort Max moving
into ern WA Sat nt, shearing and weakening as it does. However,
there will be a chance of nocturnal (overnight) showers or
isolated thunder both Fri nt and Sat nt. The afternoon thunder
threats will be located mostly across the Idaho Panhandle and NE
WA. Based on the cape/deep lyr shear combo, widespread strong
thunderstorms are not expected. New fire starts will potentially be
an issue though. Bz

Sunday evening through Thursday...subtle deamplification of the
persistent long-wave ridge that has remained in place for quite
some time takes place during this interval. The other persistent
features such as the offshore trof/Gulf of Alaska low pressure
area an another trof/low pressure area over eastern Canada remain
in place as well helping to "lock" our long-wave ridge in place.
The ridge axis remains generally in Montana for most of the
interval which means there could be some clutter/disturbances/moisture
coming up from the south or southwest off the east Pacific which
could affect our sensible weather in the form of clouds and/or
some thunderstorm potential. /Pelatti

&&

Aviation...
00z tafs: VFR conditions expected the next 24 hours. Cumulus over
the mountains will dissipate W the setting sun. Cirrus has already
begun to move into eastern Washington. Isolated thunderstorm development
is possible from the blue mtns to Lookout Pass thru 04z. We will
also have to watch for the potential for a few elevated
showers/thunderstorms moving up the Cascades overnight into Friday
morning, but the threat of it passing any taf sites is low. Shower
and thunderstorms will become more widespread as we move into mid-
late Fri aftn and evening.

&&

Preliminary point temps/pops...
Spokane 66 95 66 92 66 92 / 10 10 10 20 20 10
Coeur D'Alene 61 94 62 91 63 90 / 10 10 10 20 20 20
Pullman 58 94 57 92 59 91 / 10 20 20 20 20 10
Lewiston 71 100 69 97 71 97 / 10 30 30 20 20 10
Colville 57 97 59 95 58 94 / 10 10 20 20 20 20
Sandpoint 53 92 56 88 56 87 / 10 10 20 20 20 20
Kellogg 59 90 62 88 62 86 / 10 20 20 30 20 20
Moses Lake 66 99 64 97 65 97 / 10 20 20 20 20 10
Wenatchee 71 97 71 96 71 97 / 10 20 20 20 20 10
Omak 65 101 68 96 67 96 / 10 30 30 20 20 10

&&

Otx watches/warnings/advisories...
Idaho...heat advisory until 8 PM PDT this evening for Lewiston area.

Washington...Fire Weather Watch from Friday morning through Friday evening
for East Washington central Cascade mountains (zone 682)-
East Washington central Cascade valleys (zone 677)-East
Washington north Cascades (zone 685)-East Washington
northern Columbia Basin (zone 673)-East Washington
Okanogan/Methow valleys (zone 684).

Flash Flood Watch from Friday morning through Friday evening for
east slopes northern Cascades-Okanogan Valley-Wenatchee
area.

Heat advisory until 8 PM PDT this evening for lower Garfield and
Asotin counties.

Fire Weather Watch from late tonight through Friday evening for
East Washington south central Cascade mountains (zone 680)-
East Washington south central Cascade valleys (zone 676).

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