Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 300922
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
222 AM PDT Tue Aug 30 2016

.SYNOPSIS...
An approaching weather system will slowly cool the region through
Thursday and bring an increasing potential for showers and
thunderstorms as the week wears on. This upper level trough will
move into the region late in the week, ushering in cooler
temperatures and showery conditions for the beginning of the
holiday weekend.

&&

.DISCUSSION...

Today through Wednesday...Another interval of time influenced by
southwest flow setup with offshore trof that moves closer to the
coast. A fairly well defined shortwave feature is evident on the
water vapor satellite feed approaching the Northern California
coast. This shortwave is depicted in most of the short term models
to pass through Eastern Washington and Northern Idaho after 5 pm
today and as such is mentioned in the "Tonight" portion of the
forecast in the form of thunderstorms while increasing clouds and
mostly cloudy wording is preceding it in the "Today" portion of the
forecast. The shortwave exits overnight and leaves a lull in the
forecast until the somewhat conditionally unstable airmass contained
in the trof that moves in closer from offshore has more of an
influence over part of the East Slopes of the Cascades closer to the
crest. Forecast temperatures show a gradual cooling trend into
Wednesday due to this pattern change (trof moving closer to the
area). /Pelatti


Wednesday night through Tuesday...In the big picture an upper
level low pressure system is currently dropping south along about
140w ad is progged to move into the Pac NW Thursday and Friday and
finally kick east of the region on Sunday. The models are in good
shape with this scenario although the GFS is trying to bring a
much stronger secondary wave through the region on Sunday. This
may after all be the correct solution, but for now will lean in
favor of a faster open wave kicking east into Montana on Sunday
the region into a drier northwesterly flow.

Wednesday night and Thursday...Wednesday night and Thursday the
leading edge of the upper low tracks to just about the Cascade crest
before stalling as a second deeper wave drops down the back side
of the trough. Southerly flow will increase mid and upper level
moisture and will increase the chances for showers and
thunderstorms Wednesday evening through Thursday afternoon. We
might see showers get as far east as the Columbia river Wednesday
night, but there is a much better chance the these to remain along
the crest.

Thursday night through Saturday...The second disturbance rounds the
bottom of the trough Thursday night and allows the cold front to
track east across the forecast area. This is when the best forcing
and instability will occur and with plenty of moisture to work
with should result in widespread showers and a chance for
thunderstorms. Light to moderate rain amounts can be expected with
between 0.15 to 0.25 of an inch rain possible for the higher
terrain around the basin and less than 0.10 for the basin. The
focus of the showers gets pushed into the northeast Washington and
Idaho Panhandle mountains Friday night and Saturday as the trough
swings through the region. Temperatures will cool from the upper
70s and lower 80s Thursday to the upper 60s to lower 70s Friday
and Saturday. Winds will be out of the southwest 5 to 15 mph with
gusts 20 to 25 mph.

Sunday through Tuesday...The trough will get kicked east on Sunday
putting the region in a drier northwesterly flow. Several weak
waves will move through the the area at times and should have
enough energy to generate isolated to scattered afternoon showers
for the Northern ans eastern mountains, otherwise the forecast is
dry. Temperatures will rebound back into the lower 70s but remain
on the cool side of normal. Tobin

&&

.AVIATION...
06Z TAFS: Mid and high level clouds will move in from the south
over the next few hours. Clouds will become thicker through the
morning hours. There is a threat of VCTS for all TAF locations
except MWH Tue aftn...mainly from 22z-04Z. Confidence is not high
on thunder at the taf sites, therefore kept it VC.


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        86  59  81  56  73  52 /  10  20  10  10  10  40
Coeur d`Alene  87  56  81  54  74  51 /  10  20  10  10  10  50
Pullman        84  53  80  51  73  48 /  10  20  10  10  10  60
Lewiston       90  60  87  59  79  55 /  10  20  10   0  10  50
Colville       89  53  83  51  75  47 /  10  20  10  10  10  20
Sandpoint      86  52  81  50  73  48 /  10  20  10  10  10  50
Kellogg        86  53  81  51  73  47 /  10  30  10  10  10  40
Moses Lake     87  55  83  54  76  51 /   0  10  10  10  10  20
Wenatchee      86  61  81  58  74  53 /  10  10  10  20  10  20
Omak           90  56  85  52  77  50 /  10  10  10  20  20  20

&&

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

$$



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