300
FXUS66 KOTX 182144
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
244 PM PDT Wed Sep 18 2024

.SYNOPSIS...

Weather will trend drier toward the end of the work week, then
light rain chances mainly for the mountains Sunday into Monday. A
ridge of high pressure will deliver above normal temperatures
early next week.

&&

.DISCUSSION...
Wednesday night through Friday: The Inland Northwest is currently
sitting under a broad north to northwest flow aloft as an upper
level low moves south across California and another one moves
northeast across eastern Montana and western North Dakota. Weak
ridging over the Inland Northwest tonight into early Thursday will
allow temperatures into the 70s across much of the region and low
80s along the lower valleys in central Washington, the Columbia
Basin, and the L-C Valley. A system moving across British Columbia
Thursday afternoon into Friday will bring a dry and weak cold front
across the Inland Northwest Thursday night. Increased onshore flow
ahead of the front will bring breezy winds through the Cascade gaps
Thursday evening. The NBM is indicating the Inland Northwest to
remain dry with this, with only a 20 percent chance for 0.01 inches
of precipitation at the Cascade crest and far northeast Idaho
Panhandle. Behind the front, temperatures will cool by a couple
degrees and winds will become breezy from the north through the
Okanogan Valley, upper Columbia Basin, and the lee of the Blue
mountains Friday morning and afternoon.

Saturday through Wednesday: Drier air moving into the region within
a northwest flow aloft into the Inland Northwest as the upper level
trough moves eastward across Canada will keep skies clear overnight.
A handful of models are suggesting temperatures dropping into the
low 30s across the northeast Washington valleys Saturday morning.The
National Blend of Models is giving Colville a 40 percent chance,
Chewelah a 30 percent chance, and Deer Park a 20 percent chance for
temperatures of 32 or below Saturday morning. Those still tending to
a garden across northeast Washington may want to take precaution.

Models have significantly backed off on the idea of precipitation on
Sunday with an upper level ridge building from the south deflecting
most of the precipitation chances west of the Cascades and north
into Canada. The NBM continues to carry a 15 to 20 percent chance
for precipitation across the Cascades, the northern mountains, and
the northern Idaho Panhandle, but I would not be surprised if
this continues to trend lower. A modest plume of moisture with
PWATs increasing to over 150 percent of normal accompanying this
system will bring an increase in clouds for Sunday and Monday
across eastern Washington and north Idaho.

As the ridge builds from the south, temperatures across the Inland
Northwest will warm into the 70s and low 80s for Tuesday and
Wednesday. Whether this ridge stays parked over the region into the
latter half of the week is uncertain as about 40 to 50 percent of
ensembles between Wednesday and Thursday show a cold front moving
through the Pacific Northwest. This would bring cooler, possibly
wetter, and breezier conditions. There is disagreement within
this subset of ensemble members on the strength and speed of this
system. The other 50 to 60 percent of ensembles keep in place
with warm and dry weather continuing.  /vmt

&&

.AVIATION...
18Z TAFS: Broad north to northwest flow aloft today as a weak
ridge builds into the region. Clear skies will allow for VFR
conditions to prevail across the TAF sites, but low level moisture
may result in patchy stratus across the northern valley airports
around Deer Park early Thursday morning.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
for VFR conditions to continue for the TAF sites. There is a 10 to
15 percent chance for marginal VFR ceilings at Deer Park and
Colville between 12-17Z Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        49  75  47  72  43  71 /   0   0   0   0   0   0
Coeur d`Alene  48  74  47  69  43  70 /   0   0   0   0   0   0
Pullman        44  72  45  65  39  67 /   0   0   0   0   0   0
Lewiston       54  81  53  74  50  75 /   0   0   0   0   0   0
Colville       39  75  36  71  32  70 /   0   0   0   0   0   0
Sandpoint      45  71  43  68  36  68 /   0   0   0  10   0   0
Kellogg        50  72  48  65  45  66 /   0   0   0   0   0   0
Moses Lake     46  79  46  74  42  73 /   0   0   0   0   0   0
Wenatchee      54  79  54  72  48  74 /   0   0   0   0   0   0
Omak           51  81  47  74  46  75 /   0   0   0   0   0   0

&&

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

$$