Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 241156
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
456 AM PDT Mon Apr 24 2017

.SYNOPSIS...
Expect cool, breezy, and showery weather this week. The most
widespread precipitation will likely occur Tuesday night into
Wednesday with the potential for a half inch or more of rain over
portions of the Idaho Panhandle and southeast Washington. A ridge
of high pressure next weekend has the potential to bring the
region a day or two of drier weather.

&&

.DISCUSSION...
Monday: One shortwave disturbance is pivoting across the Okanogan
Highlands to the North Panhandle while a low pressure circulation
is moving into southeast WA/northeast OR. The batch of showers
across the northern mtns will continue to shift north into Canada
through the morning hours. The stronger batch of energy off the
WA/OR coast has better dynamics and support from the upper level
jet. The surface low associated with this system is located just
off of the northeast OR coastline with the warm front spreading
into northern OR and southern WA early this morning. The trend
will be for precip to continue to spread along the southern
portion of the forecast area along the front this morning with
best chances over southeast WA and into the southern/central ID
Panhandle.

The surface low will rough track right along the WA/OR border
through today and the exit to the southeast tonight. A cloudy and
showery day is in store for the southeast corner of the forecast
area. Mid to high level clouds will be abundant across much of the
region today as well, so not expecting to see much if any
sunshine for the start of the work week. We will destabilize in
the afternoon with colder temperatures aloft creating a
conditionally unstable environment. Pop up showers are expected
this afternoon over much of the region, even across the northern
areas away from the low pressure circulation.

Tuesday: The northern branch of this incoming trough will push
across on Tuesday. Best forcing and precip chances will be across
the northeast portion of the region. The rest of eastern WA will
see drier conditions with a better chance for the sun to peak
through. With that said, we will see higher clouds increasing over
the Cascade Mtns ahead of the next weather system set to move in
Tuesday night. /SVH

Tuesday night through Thursday...Zonal flow will buckle Tuesday
night as an upper level disturbance moves through the region on
Wednesday and digs into the Great Plains on Thursday. The westerly
flow will draw an Atmospheric River into the region with the
focus mainly over the southern Oregon and California. While the
moisture deepens across Washington to 150-200 percent of normal,
our area will get a fraction of the moisture that areas further to
the south can expect. With the exception of the ECMWF the models
are coming in with more precipitation amounts and pops were bumped
up accordingly.

The westerly flow will create a shadow in the lee of the Cascades
with the lower east slopes and the Columbia Basin seeing very
little measurable precipitation. The Cascade crest could see
anywhere from a quarter to a half inch with around three quarters
of an inch possible right at the crest. East of a line from about
Republic to Ritzville we can expect from a quarter of an inch to
around a half inch for Spokane-Coeur D`Alene metro and Pullman,
then between a half inch to around an inch for the central
Panhandle mountains. Snow levels will be between 4500-5500 feet
for high mountain snow. The snow levels will decreases to around
3500 feet by Thursday morning, but by this time the precipitation
will decrease quite a bit. Snow amounts for the higher elevations
will still be around 3-7 inches through Thursday morning.

A cold front will track across the area Wednesday evening and bring
drying from the west with orographic showers continuing for the
Panhandle mountains. The front will also tighten the surface
gradient and allow 35-40kts 850 mb winds to mix down to the
surface. Expect breezy/gusty winds to be on the increase late
Wednesday day morning and increase through the afternoon before
decreasing Wednesday night. Southwest winds 20-30 mph with gust
30-40 mph will be possible Wednesday afternoon and Wednesday
evening.

Thursday through Saturday morning...High pressure will build in
the eastern Pacific on Thursday and move to about 130W by Friday
night. The flow will come around to northwest on Thursday and
finally northerly on Friday. Plenty of weak waves will be embedded
in the flow and while we will lose the deep moisture tap there
will be enough lingering moisture and afternoon instability to
support showers for most places outside of the Columbia Basin.
Temperatures will cool off behind the cold front on Thursday with
highs mainly in the 50s on Thursday then rebounding several
degrees for Friday, but still below average. Tobin

Saturday through Monday: The weekend will start off under the
influence of an upper ridge which means a pleasant Saturday
morning with most everyone staying dry. Models disagree somewhat
on how quickly this ridge will break down, but I`m leaning toward
a EC/GFS solution, as the Canadian remains the outlier. The next
in a series of disturbances moves in during the afternoon.
Saturday`s ridge is quite flat, so as this wave moves through and
brings moisture and lift to the region, flow becomes zonal. This
will keep the lee of the Cascades and deep basin rain shadowed,
and most of the rain chances Saturday into Sunday will be
relegated to the mountains and eastern basin. With low level
southwesterly flow, temperatures will be on the uptick each day.
By Sunday we`ll be back into the upper 50s and mid 60s. /bw

&&

.AVIATION...
12Z TAFS: Widespread showers and low cigs are expected at KGEG,
KSFF, KCOE, KPUW and KLWS on Monday. A low pressure system is
situated just off of the northern OR coastline early this morning
and will slowly migrate along the WA/OR border over the next 12
hours. Moisture will wrap into the region around the low with
light rain expected at KPUW and KLWS through the morning.
Increasing boundary layer moisture will lower cigs to between 1-3
kft agl at KPUW and KLWS with southerly winds advecting this
moisture into the Spokane-Coeur d`Alene corridor as well.
Precipitation will transition to showers for the afternoon and
expand across much of the region. Expect cigs to lift slightly in
the afternoon to between 3-5 kft with mountains likely being
obscured by the cloud cover. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        54  40  56  42  54  37 /  60  20  40  60  70  60
Coeur d`Alene  53  39  54  39  53  35 /  60  30  40  70  80  70
Pullman        52  40  55  43  52  38 /  70  50  20  80  80  60
Lewiston       57  44  60  46  57  42 /  60  60  30  70  60  50
Colville       58  38  57  41  56  37 /  50  20  40  50  70  60
Sandpoint      52  36  52  37  52  36 /  50  20  50  60  90  70
Kellogg        49  36  50  37  49  36 /  70  60  50  80  90  70
Moses Lake     60  39  62  44  60  41 /  30  20  10  30  20  10
Wenatchee      57  41  60  42  58  40 /  30  20  10  20  20  10
Omak           60  37  63  42  60  38 /  20  20  10  20  30  20

&&

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

$$


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