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Area forecast discussion 
National Weather Service Spokane Washington
440 PM PDT Friday Aug 29 2014

Synopsis...
the Labor Day weekend will be cooler than normal with locally
breezy conditions over portions of central and eastern
Washington. With the exception of some isolated mountain showers,
the majority of the inland northwest will remain dry through the
weekend. A continuation of the cool weather pattern is expected
through next week. The best chance for showers and thunderstorms
will probably occur in the Wednesday or Thursday time frame.

&&

Discussion...

Tonight and saturday: the issues will be thunder chances, gusty
Cascade Gap winds, and cloud-cover/temps. The frontal passage
should present the main focus as gusty winds and pressure
gradients continue to increase across the Cascades. These observed
differences support gusts to 35 mph in the Cascades gaps
(wenatchee,etc). Cloud cover tonight will help to keep low temps
warmer than last night for north Idaho, limiting the fog potential
significantly from what we saw this morning. We have a slight
chance of rain showers across the nrn WA and Cascade zones this
evening, though with hourly pcpn rates from a trace to a hundredth
today with this frontal band, only very light, or no pcpn is
expected. For thunder, it doesn't look like there's much chance at
all, especially with the high boundary lyr convective inhibition
over nrn WA. This is true also for the Camas Prairie of Idaho near
Lewiston early evening, but to a much lesser extent. This is our
best chance though for thunder this evening. The Post-frontal dry
slot will keep skies sunny, cooler and breezy Saturday for most
zones. Still...the best chance of isolated thunder/showers will
be near the British Columbia border and Camas Prairie of Idaho. Bz

Saturday night through Monday night: the region will be in
northwest flow aloft which will keep temperatures on the cool side
of seasonal normals for the Holiday weekend. Some moisture and
energy will ride along the large scale flow, bringing scattered
showers to the area but this will likely be limited to the higher
elevations. The only threat of thunderstorms will be for the NE Washington
mts and extreme north Idaho for Saturday evening. This will end overnight
as the instability associated with the cold pool aloft moves east.
Persistent northwest flow will mean partly cloudy skies, breezy
winds at times, and cooler temperatures. Daytime readings will be
in the 70s to low 80s for most valley locations. Overnight lows
will start to get a bit chilly for the northern sheltered valleys
where mid 30s will be possible. /Kelch

Tuesday through friday: a trough settles into the region, with a
few showers and cool conditions. Tuesday to Wednesday a cold front
tracks through southeast Washington/lower Idaho Panhandle into the Great Basin. The
frontal passage looks relatively dry. However the upper trough on
its heels and deformation axis wrapping back toward the northern
mountains sags in. Moisture pooling in this deformation axis, in
tandem with lift and instability with the upper trough, will bring
a shower and thunderstorm threat. On Tuesday into Tuesday night
the chances will be around the Cascades and northern mountains
zones. On Wednesday chances continue in this region, but expand
south toward the Highway 2/1-90 corridor (between the eastern
Waterville Plateau to the c'da area) as that deformation axis sags
south. Still, the best chances will remain closer to the
mountains. Between Wednesday night and Friday model agreement
falters. Loose agreement shows the upper trough stretches
northeast toward the High Plains and a second trough digs south
along the or/California coast. This leaves a weak mid-level trough over
the inland NW, but not really much significant forcing. In
addition, the atmosphere begins to dry out. On Thursday pockets of
convective instability linger around the Cascades and northern
mountains. On Friday some instability come toward central Idaho
with the developing southwest flow, bordering southeast Washington and the
lower Panhandle. So some slight shower chances will linger in
these areas, on their respective days. Otherwise look for mostly
dry conditions with a few clouds. Below normal temperatures are
expected through this period, but look for some moderation late
week as the trough loses its resolution. /J. Cote'

&&

Aviation...
00z tafs: VFR conditions are expected to continue through 00z
Sunday. A weak cold front will passing through early this evening
will result in mid and high clouds and gusty winds. Winds will
subside overnight as pressure gradients relax and mixing potential
decreases. Behind the front an increase in low level moisture
Saturday morning and upslope flow into the high terrain in
southeast Washington will result in an area of stratocumulus but
ceilings at puw should remain VFR. A few showers are possible over the
mountains this evening with the passing cold front...as well as
Saturday afternoon as the atmospheric begins to destabilize
especially near the Canadian border. Winds will become gusty again
Saturday afternoon. Jw

&&

Preliminary point temps/pops...
Spokane 53 73 50 70 52 73 / 0 0 10 10 10 10
Coeur D'Alene 52 72 47 69 48 72 / 0 0 10 10 10 10
Pullman 50 72 45 71 46 73 / 0 0 10 10 10 10
Lewiston 60 78 54 77 56 80 / 10 10 10 10 10 0
Colville 46 76 44 73 44 77 / 10 10 10 10 10 10
Sandpoint 51 70 42 68 44 69 / 10 10 20 10 20 10
Kellogg 52 68 47 66 49 70 / 10 10 20 20 20 10
Moses Lake 50 79 50 77 50 80 / 0 0 0 0 0 0
Wenatchee 56 77 57 76 57 79 / 0 0 10 0 0 0
Omak 52 79 51 75 51 79 / 10 10 10 10 10 0

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&

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