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Area forecast discussion 
National Weather Service Spokane Washington
433 PM PDT Friday Aug 22 2014

Synopsis...
showers and thunderstorms will decrease tonight with the threat
for flash flooding decreasing this evening. Mainly an isolated
shower threat over the mountains on Saturday with a better chance
of showers and thunderstorms expected Sunday for this weekend. A
drier and warmer weather pattern is expected for the new work
week.

&&

Discussion...
tonight: satellite imagery indicates that the low pressure system
is situated right over southeast Washington/northeast or. The best
combination of lift and instability is located along the southeast
quadrant of the low. This is where we are seeing the best
thunderstorm activity into this afternoon. This moisture will
continue to wrap itself around the low into the northern
Panhandle, across northeast Washington and wrap into the east slopes of
the Cascades and into western basin. This area will also continue
to destabilize through the late afternoon hours. Due to a lack of
large scale lift across these areas, I don't think thunderstorms
will be as prevalent or become as strong. With that said, there
will continue to be a risk for flash flooding and debris flows on
the burn scars as these thunderstorms will be slow moving and
have the potential of training over one area. The Flash Flood
Watch remains valid for the east slopes of the Cascades and no
changes are anticipated for the rest of today. Showers and
thunderstorms will begin to wane through the evening and
generally be confined to extreme eastern Idaho and into Montana
overnight.

Saturday into Saturday night: this will be a break period between
weather systems. Soundings show the potential for a lot of flat
cumulus cloud cover over the region. I don't see a good potential
for shower activity during the afternoon on Saturday with a
capping inversion at about 12 kft, but did keep a chance of
showers over the mountains. Temperatures are expected to warm up a
little bit across eastern Washington to near normal. The Panhandle will
likely remain below normal for mid August. The next weather system
will begin to enter into the region from the northwest Saturday
night. Mid levels will begin to destabilize and I increase precip
chances a little bit mainly across the northern mountains
continuing into Sunday morning. /Svh

Sunday through Friday...another upper level trough will drop south
out of British Columbia into the inland northwest on Sunday
bringing another round of showers with embedded thunderstorms.
Models have trended wetter with a bit more instability over the
area. Lingering low level moisture will add to the instability and
thus confidence is good in this trend and have increased pop's.
Very minimal shear will result in storms being the short lived
type with brief heavy rain and small hail. On Monday the trough
axis shifts east into Montana. A lingering cold pool aloft over
the Idaho Panhandle and possibly extreme eastern Washington will
result in residual shower activity and possibly a stray
thunderstorm. An upper ridge will then build in Tuesday and
Wednesday for warmer and dry conditions. On Thursday and Friday
the ridge begins to flatten in response to an upper low dropping
southeast from the Gulf of Alaska. A gradual cooling trend is
likely Thursday and Friday.

Looking just beyond current forecast period...if current models
pan out the upper low moves into the region over Labor Day weekend
with some model consistency supporting this idea. This would
result in more significant cooling and a chance of showers. Jw

&&

Aviation...
00z tafs: an upper level area of low pressure will continue to
remain overhead of most of the aviation area tonight so showers
and thunderstorms with brief MVFR ceilings and visibilities under
the more intense thunderstorms may occur. This low should make
slow progress southeast and away from the aviation area late
tonight and tomorrow and be less of an influence so the forecast
shows a general drying trend into tomorrow with the expectation
there will be some afternoon and evening cumulus development.
/Pelatti

&&

Preliminary point temps/pops...
Spokane 55 76 55 76 56 80 / 30 10 10 40 40 10
Coeur D'Alene 53 73 53 76 53 78 / 30 10 10 40 40 20
Pullman 50 75 50 77 51 80 / 40 10 10 40 40 20
Lewiston 59 81 58 82 59 85 / 50 20 10 20 20 10
Colville 50 80 50 78 52 82 / 60 10 10 60 60 10
Sandpoint 49 71 48 72 49 75 / 40 20 10 50 50 20
Kellogg 50 67 49 69 53 74 / 40 20 20 50 50 30
Moses Lake 56 83 56 84 56 86 / 50 0 0 20 20 0
Wenatchee 61 83 60 82 62 85 / 60 0 0 20 20 0
Omak 57 84 56 82 55 86 / 50 0 10 30 30 10

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...Flash Flood Watch until 9 PM PDT this evening for east slopes
northern Cascades-Okanogan Valley-Wenatchee area.

&&

$$

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