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Area forecast discussion 
National Weather Service Spokane Washington
432 PM PDT Friday Jul 11 2014

Synopsis...

A prolonged heat wave will continue across the inland northwest
through this weekend and may linger well into next week. Mid to
upper 90s will be common, with triple digit heat in the Lewiston
area and portions of the Columbia Basin. There will be potential
for monsoonal moisture to invade the region early next week, with
some threat of thunder, but otherwise the forecast is dry.

&&

Discussion...
tonight through Saturday night...a strong upper level ridge will
persist bringing continued hot and dry conditions. One possible
exception is the east slopes of the Cascades where a weak
disturbance over southern Oregon today will lift north on the back
side of the building ridge into the east slopes of the Cascades
Saturday afternoon and evening. The models weaken this
feature...however there may be just enough instability to trigger
a few thunderstorms although confidence is not very high that we
will see any thunderstorms. The NAM has consistently been more
unstable but the latest 18z run has trended towards less
convection. With the lower levels being very dry...and the
GFS/European model (ecmwf) showing a lesser threat compared to the NAM...forecast
leans towards the drier solution. However a slight chance was kept
in the mountainous terrain along the east slopes due to the
uncertainty. Another small exception is over the mountainous
terrain over the north Idaho Panhandle through early this evening.
A few cells have popped up on radar associated with a weak
disturbance clipping the area. These will be very isolated and
short in duration as mid level drying and warming moves in by this
evening. Jw

Sunday through Monday night...high pressure with warm temperatures
and very dry relative humidity will be the story through this
portion of the forecast. The second and maybe more important
challenge will be the closed low off the California coast. The
models are indicating this low to move north along the
coast...then push inland Sunday night and Monday. Pattern wise
this a good set up for thunderstorms. The timing of the wave
moving through the Cascades is between about 03 to 15z Sunday
night and Monday give or take a few hours. Stability wise there is
plenty of mid level cape, lapse rates, and hltt. There is also
plenty of moisture to work with as pwat's are between .60-.80
which is 100-130 percent of moisture. The issue is that cross
sections and model soundings show the moisture around 600mb. There
may be a fine line between thunderstorms and just high level
clouds. For now we went slight chance for Sunday night and will
monitor further. Nocturnal thunderstorms typically don't result in
a lot of precipitation making it to the ground anyway, and this
may be a fire weather challenge through early Monday morning. We
will typically see a break in the convection soon after sunrise,
with surface based convection later in the afternoon. By this time
the focus will have shifted to the northern Washington mountains and the
Idaho Panhandle mountains and thunderstorms should become much
wetter. Temperatures may be tempered a few degrees by clouds, but
will still be above normal. Min temperatures will likely be very
mild with cloud cover. /Tobin

Tuesday and wednesday: ridge of high pressure will strengthen
back over the region for Tuesday and Wednesday. This will once
again result in hot afternoon temperatures. Highs are expected to
be back up into the upper 90s to over 100 degrees for many
locations. These temperatures will be hot enough that a heat
advisory may be needed as we move into early next week; however,
it still only looks marginal at this point, so confidence is low
that highlights pertaining to the heat will be needed.

Wednesday night through thursday: models are keying in on a cold
front passage around this time. Even though we should largely stay
dry with this front, there is a small chance for some thunderstorms
to develop along the Blue Mountains ahead of the front. If any
thunderstorms do develop, they could track northeast across the
central Idaho Panhandle.

The main concern with this front will be for breezy winds. These
winds will pick up through the Cascade gaps late Wednesday
afternoon or early evening and then peak during the afternoon on
Thursday. Strongest winds with gusty conditions will be possible
through the Cascade gaps and out into the western basin. This area
will continue to be dry and gusty winds may result in critical
fire weather conditions, especially for Thursday afternoon/evening.

Friday: high model uncertainty with the 12z European model (ecmwf) solution
transitioning into a dry northwesterly flow pattern, whereas the
12z GFS solution drops down a closed upper level low pressure
system into western Washington. The GFS solution would be a more favorable
set up for precip and thunderstorms; however, this is a new
development compared with the previous run, so confidence is
higher in the European model (ecmwf) solution compared to the GFS at this time.
Either solution would support a cooling trend with temperatures
dipping closer to normal by Friday. /Svh

&&

Aviation...
00z tafs: area wildfires will produce occasional haze and smoke
layers aloft, especially at eat. Otherwise VFR conditions will
prevail at all taf sites, with occasionally thicker middle and
high clouds coming up from the south. There may be some isolated
showers/thunderstorms near the crest of the Cascades Saturday
afternoon as an upper weather disturbance slips up the west side
of the ridge of high pressure. Otherwise look for continued dry
weather. /J. Cote'

&&

Preliminary point temps/pops...
Spokane 65 96 67 99 67 95 / 0 0 0 0 10 10
Coeur D'Alene 58 94 60 97 64 93 / 0 0 0 0 10 20
Pullman 53 95 53 97 60 95 / 0 0 0 0 10 20
Lewiston 63 102 67 104 70 101 / 0 10 10 0 10 20
Colville 55 99 58 103 62 97 / 0 0 0 0 20 20
Sandpoint 53 92 52 98 59 91 / 0 0 0 0 10 20
Kellogg 58 94 59 94 61 91 / 0 0 0 0 10 30
Moses Lake 63 102 66 102 70 103 / 0 0 0 10 10 10
Wenatchee 67 100 71 102 72 100 / 0 10 10 10 10 10
Omak 60 101 65 104 66 98 / 0 0 10 10 20 20

&&

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

$$

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