Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 230444

Area Forecast Discussion
National Weather Service Spokane WA
944 PM PDT Fri Sep 22 2023


The weekend will be mainly dry with chances for rain in the
Cascades on Saturday and northeast Washington and far north Idaho
Sunday morning. An active jet stream will be directed into the
Pacific Northwest next week. From Monday through at least Friday,
periods of rain and breezy winds are in the forecast as a series
of systems move through the region.



Tonight: Rain bands wrapping around a slow moving low in southern
Idaho will decrease late in the afternoon into the evening. These
bands have been most concentrated over the Idaho Panhandle so far
today. As of 2 PM, rain gages in Shoshone county had reported
between a tenth and a third of an inch of rain the highest
readings around Lookout Pass, Osburn, and in the upper reaches of
the St Joe River. As the center of the main upper low moves out of
southern Idaho into Wyoming, the deformation band will move
eastward as well. A 20 to 30 percent chance of light rain will
linger into the mid to late evening from Lookout Pass to Sandpoint
and Bonners Ferry before retreating toward the Canadian border
during the early morning hours. Areas of fog will be possible in
the valleys of far north Idaho and northeast Washington before
sunrise in places like Priest River, Metaline, Cusick, and
Newport. Clouds and higher humidity will keep temperatures in
north Idaho and northeast Washington mild compared to some of our
recent chilly nights. Overnight lows will be in the 40s and low
50s across most of the Inland Northwest.

Saturday: Our next low pressure trough will follow quickly on the
heals of tonight`s departing low. The majority of the Inland
Northwest will be dry Saturday and Saturday night with
temperatures climbing into the upper 60s and low 70s. But some
spots will have chances for rain. Clouds and bands of light rain
will increase across western Washington and the northern Cascades
during the Saturday and Saturday evening. Rain amounts with the
initial arrival of this trough will be light over the Cascades
compared to what is expected early next week, but folks living
downwind of fires (degraded air quality) like the Airplane Lake
and Dome Peak should be pleased that these fire should get wet
Saturday and Saturday evening. The National Blend of Models gives
these fires a 50 to 70 percent chance of getting a tenth of an
inch of rain by Saturday evening and a 30 percent chance of a
quarter inch.

Sunday: There is good model agreement that our region will
experience a mainly dry day on Sunday as a large area of low
pressure organizes off the coast. The morning runs of the NAM,
ECMWF, and GFS have latched onto an early morning shortwave and a
stripe of showers across the West Plains, Pend Oreille, Bonner and
Boundary counties. A 20 to 40 percent chance of morning rain has
been added to the forecast for this early morning precipitation,
but the remainder of the day should be dry with afternoon
temperatures in the 60s under increasingly cloudy skies. /GKoch

Sunday night through Friday:
The overarching pattern through next week will feature rain,
cooler than normal temperatures, and breezy winds due to a
persistent trough that will hover over the Northwest. The trough
will develop offshore early in the weekend will rapidly
strengthen on Sunday forming a closed low, which will direct a
stream of moisture from an early- season atmospheric river
straight into the West Coast. While soggy conditions will almost
certainly be in store for Western Washington, Eastern Washington
likely won`t see much rain...until later. The low will be
positioned far enough off the coast that ridging to its east will
temporarily shield the Inland Northwest from the incoming

Heading into early next week, models still haven`t come to an
agreement on when exactly precip will begin for us. Nearly all
models show widespread precip moving in at some point on Monday.
It`s just a matter of when. The timing of the precip will have a
significant influence on Monday`s high temperatures. Some models
show a faster-moving low heading inland and bringing widespread
showers as early as Sunday night, while others show a stronger,
slower low not making it here until Monday night. If the low and
it`s associated precip arrive earlier, Monday`s high temperatures
will be on the cooler side in the low 60s, but if the low doesn`t
reach us until late Monday, temperatures could rise into the upper
70s. That`s a big range!

By Monday night and into Tuesday model consensus is much better,
showing cooler temperatures and abundant moisture taking over
with showers regionwide. 48-hour precip totals between Sunday
night and Tuesday night are around a tenth of an inch over the
Columbia Basin, 0.2 inches for Wenatchee and most of the Idaho
Panhandle, 0.4 to 0.6 inches over the Northern Mountains, and near
an inch for the Cascade Crest. This will be very beneficial rain
for the Airplane Lake and Blue Lake fires and will substantially
mitigate smoke production from said fires.

Temperatures will stay cool in the upper 50s to mid 60s through
the end of next week as the trough remains stationed over us.
Intermittent showers will continue to impact the region as smaller
disturbances ripple through the larger trough, bringing waves of
moisture with them. /Fewkes


06Z TAFS: The upper low continues to move eastward and high
pressure builds into western and central Washington. Low clouds
will spread into north Idaho and far northeast Washington. Places
like Sandpoint, Bonners Ferry, Priest Lake and Colville will
likely experience a cloud deck of 3000 to 5000ft btwn 10Z and 16Z.
There is a less than 10 percent chance of advection fog or low
stratus at Spokane International as moisture over the Palouse is
drawn to the north overnight. It has been handled with VCFG in the


Spokane        46  70  49  67  51  71 /  10  10  20  20  10  30
Coeur d`Alene  47  70  48  67  50  71 /  10  10  10  20  10  20
Pullman        40  69  43  67  49  72 /  10   0   0  10  10  20
Lewiston       47  77  51  73  54  79 /  10   0   0   0  10  10
Colville       44  69  40  65  42  67 /  10  10  10  20  20  40
Sandpoint      44  68  44  65  47  69 /  30  10  20  20  20  20
Kellogg        48  68  49  66  51  71 /  30  10  10  10  10  20
Moses Lake     44  71  47  67  51  70 /   0  10   0  10  30  50
Wenatchee      50  69  50  64  54  65 /   0  10  10  10  60  60
Omak           51  71  48  68  53  68 /   0  10  10   0  40  50



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