Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 200941
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
241 AM PDT SAT SEP 20 2014

.SYNOPSIS...
Strong high pressure will provide a generally clear...warm and
dry weekend for the Inland Northwest. The new work week will start
out with continued above normal temperatures...but a weak cold
front will bring a chance of showers starting Tuesday. From mid-
week onward an approaching deep trough will increase the
probability of rain with cooler temperatures.

&&

.DISCUSSION...
Today through Sunday night...A ridge of high pressure will build
over the region, keeping dry conditions and warming temperatures
over the Inland Northwest. Surface high pressure will shift to the
east side of the continental divide, promoting northeast flow.
This will bring dry continental air into the region that will
downslope into the Columbia Basin, drying it further. Mostly clear
skies will promote daytime temperatures about 10 to 15 degrees
above seasonal normals for the weekend. By Sunday night some
monsoonal moisture may infiltrate the southeast zones but chances
are it will bring only mid level clouds but no precipitation.
/Kelch

Mon through Wed Night...With the breakdown of the upper ridge,
we`ll see a very weak wave move NE across the region Mon and Mon
Nt. Given the lack of deep instability over a dry sub- cloud
layer, it is not expected to produce much more than some clouds
for Mon Nt. Confidence is not high that this short-wave will be
dry though, mainly because model guidance shows a decent signal
for the possibility of high- based convective pcpn Mon into Tues
morning first in the Cascades, then spreading NE. The ECMWF was by
far the wettest with this feature compared to previous Nam and Gfs
runs. The latter models have trended slightly wetter, so this will
need to be watched. A slow- moving cold front is expected to make
landfall Tues Nt and Wed morning along the Pacific Nw coast. We`ve
been favoring a slower trend of this front as far as its Ewd
progression based on model trends and pattern recognition applied
to the north-south shearing offshore trough. The downstream
effects of this shearing will be a more meridional steering flow
over Ern Wa and N Idaho, leading to a more persistent thermal
ridge and warm, dry wx likely extending into Wed for most towns.
Confidence is increasing that this stalled front will not make
much eastward progress... likely not reaching the Idaho Panhandle.
For now, we limited the bulk of the rain through Wed Nt to the
Cascades. We warmed temperatures for far Ern Wa and the Idaho
Panhandle especially for Wed, with temps still around ten degrees
above normal. bz

Thursday through Saturday: A low off the coast of Washington and
a strong trough along the West Coast will push southern moisture
into the region. The models are having issues with the timing of
the this system as they have continued to push this pattern
further back from previous runs. Once the front pushes through the
region, rainshowers will impact most of the region and
temperatures will return to season normals of around 70. An
occasional thunderstorm is possible along the Panhandle of Idaho
as the front pushes through the region on Friday. Temperatures
will increase around 10 degrees on Saturday from the highs on
Friday. /JDC

&&

.AVIATION...
06Z TAFS: High pressure will promote dry and VFR conditions at
TAF sites, with light diurnal winds. Some patchy fog is forecast
for the sheltered mountain valleys over NE WA and north ID late
overnight and Saturday morning (09-18Z). At this time it is
expected to remain away from TAF sites. /J. Cote`

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        82  54  87  56  84  57 /   0   0   0   0   0  10
Coeur d`Alene  81  52  86  52  84  54 /   0   0   0   0   0  10
Pullman        85  50  88  51  85  54 /   0   0   0   0   0  10
Lewiston       89  57  91  60  89  59 /   0   0   0   0   0  10
Colville       84  49  87  48  86  50 /   0   0   0   0  10  10
Sandpoint      77  47  82  45  79  49 /   0   0   0   0   0  10
Kellogg        79  52  84  53  81  53 /   0   0   0   0   0  10
Moses Lake     87  54  90  55  89  55 /   0   0   0   0   0  10
Wenatchee      85  61  90  63  87  59 /   0   0   0   0  10  10
Omak           86  52  90  55  87  56 /   0   0   0   0  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$




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