Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 310958
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
257 AM PDT SUN AUG 31 2014

.SYNOPSIS...
Today will be cooler than average with scattered showers over the
mountains and breezy conditions over the Columbia Basin. Look for
winds to be a bit lighter on Labor Day with mostly sunny skies
region-wide. The arrival of a cold front Tuesday afternoon will
bring a return of breezy conditions to eastern Washington and
below average temperatures for Wednesday. A gradual warming and
drying trend is expected Thursday into next weekend.

&&

.DISCUSSION...

Today through Monday night: The region remains under the western
portion of a broad area of an upper level trough of lower
pressure. We also continue to be on the unstable side of the
upper level jet. Moist westerly flow combined with a little bit of
instability is responsible for much of the shower activity across
the ID Panhandle through the overnight hours. We have also seen
just enough instability for some lightning strikes under the
stronger cells in the Central Panhandle Mountains. The NAM model
is doing a pretty good job capturing the deeper instability where
these stronger cells are popping up. Sounding profiles suggest
that this instability will become increasingly more capped through
the morning hours, so these thunderstorms are not expected to
remain over the area for long. Showers will continue across the
Panhandle into the afternoon hours, and will then decrease
overnight has temperatures aloft warm and mid level lapse rates
continue to stabilize. Winds will once again become breezy this
afternoon similar to yesterday. All areas are expected to be dry
on Labor Day as we continue to transition over onto the stable
side of the upper level jet. Temperatures will also begin to warm
up a few degrees with highs in the 70s for most locations on Labor
Day. /SVH

Tuesday: There is good agreement between the NAM, GFS and ECMWF
that a shortwave pressure trough will drop down the British
Columbia coast on Tuesday. Current satellite imagery shows this
trough near the Aleutian Chain and by Tuesday evening this feature
should be near the Olympic Peninsula. At this time, the most
noticeable weather for eastern Washington on Tuesday looks to be
increasingly breezy conditions during the afternoon and evening
hours as the surface front crosses the Cascades. Gap winds through
the Wenatchee River valley, Lake Chelan area, and the Methow
Valley Tuesday evening will have a good chance of producing gusts
in the 25 to 35 mph range. For the Columbia Basin, Palouse and
West Plains, the pressure gradient appears to tighten during the
evening hours as the sun sets. The formation of the typical
evening inversion may inhibit mechanical mixing to the surface,
but sustained winds of 10-15mph with gusts of 20 mph or more may
still be possible given the degree of low level cold advection and
momentum aloft (25kts at 850mb).

Wednesday: The upper level trough is expected to graze northeast
Washington and far north Idaho on Wednesday bringing the best
chance for showers and thunderstorms to the mountains along the
Canadian border. Deep layer instability will be limited, so strong
storms are not anticipated. The biggest change to the Wednesday
forecast was cooling afternoon temperatures into the upper 60s to
mid 70s for the majority of the forecast area.

Thursday: An elongated 500mb trough will linger over Washington
and north Idaho on Thursday, but the majority of the mid-level
moisture and instability will shear eastward. A 20 percent chance
for light showers has been retained for the mountains of the Idaho
Panhandle and extreme northeast Washington. The remainder of the
Inland Northwest will undergo a push of light northeast winds
bringing dry dewpoints. Afternoon temperatures should rebound a
bit after Wednesday`s cool readings, but highs will remain below
average Thursday. /GKoch

Friday through Sunday night: Fairly benign weather will dominate
over the Inland Northwest during this time frame, with warming
temperatures (to just above normal for the weekend) and dry
weather expected. The mid- week trough will be exiting to the
east, and most of the extended models close off the southern
portion of the trough over northern California. Any weather
disturbance during the Friday and Saturday time frame will be
moving more into British Columbia, which should keep much of any
precipitation chances slim over the region. However, with the low
pressure sitting off the northern California coastline, some
moisture may get worked north into the Idaho Panhandle, and maybe
as far west as far SE Washington.

A stronger trough will begin affecting eastern Washington and the
Idaho Panhandle late in the weekend or early next week. The far
extended models disagree on timing with this feature, but this
should bring another period of cooling temperatures, increased
winds, and slight chances for precipitation. ty

&&

.AVIATION...
06Z TAFS: Increased low level moisture and upslope flow into the
Idaho Panhandle tonight may lead to occasional MVFR stratus at
KCOE and adjacent portions of far Eastern WA including KSFF/KPUW
between 11-16z. Scattered showers will remain possible as well
over the Idaho Panhandle.  Otherwise dry conditions with VFR CIGS
is expected through 06z Monday.  JW


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        71  50  74  51  75  50 /  10   0   0   0   0  10
Coeur d`Alene  69  47  73  49  75  49 /  20  10  10   0   0  10
Pullman        70  43  74  45  77  46 /  20   0   0   0   0   0
Lewiston       77  52  80  54  84  55 /  10   0   0   0   0   0
Colville       75  43  77  45  78  44 /  10  10  10   0  10  20
Sandpoint      68  42  71  46  74  47 /  30  20  10   0   0  20
Kellogg        65  47  68  49  72  46 /  50  10  10   0   0  10
Moses Lake     78  49  81  51  80  51 /   0   0   0   0   0  10
Wenatchee      77  54  79  57  78  54 /   0   0   0   0   0   0
Omak           78  51  79  54  79  51 /  10   0   0   0  10  10

&&

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

$$




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