Wildfire in Oregon, August 8 to 23, 2017

Area Forecast Discussion
National Weather Service Pendleton OR
239 PM PDT Tue Aug 8 2017

.SHORT TERM...Tonight through Friday evening...Mid level moisture
has been largely suppressed south into southern Oregon by a weak
wave that moved through the area earlier. Thus will see a few
cumulus clouds over the mountains, but little to no thunderstorms
today. A stray storm may develop along the Cascade crest in
Deschutes county, but these will drift west. The upper ridge over
the eastern Pacific and western U.S. will remain in place through
Thursday, though it should begin to drift east Thursday afternoon.
At the same time a weak upper low currently near 40N/130W will drift
to northern California Wednesday through Thursday. This low will
cause the currently suppressed moisture to gradually shift north
back into the region. Thus will keep some mention of showers/storms
over portions of central Oregon Wednesday afternoon/evening. The
moisture will continue to gradually spread north and northeast
Thursday. Thus will keep a mention of slight chance showers/storms
over central Oregon, the Cascade east slopes of north-central and
south-central Washington, and into the eastern mountain zones. The
weak upper low will weaken further and move northeast Friday as a
stronger upper trough approaches the region from the Gulf of Alaska.
As such, will see chances for thunderstorms spread over a larger
portion of the area. At this time, only portions of the Columbia
Basin should escape the showers/storms.

Smoke and haze will continue over the region until late week. Thus
will continue the current Air Quality Alerts. Hot afternoon high
temps with low temps in the mid to upper 60s will potentially cause
heat stress in the Lower Columbia Basin, the Columbia River Gorge,
and the Yakima and Kittitas valleys through Thursday. Thus will
continue the current Heat Advisories, though did extend the advisory
into the Washington lower basin. 90

.LONG TERM...Friday night through Tuesday...The upper level ridge
will shift east Friday night. Saturday eastern WA and OR will be on
the backside of the ridge with moisture and instability advected
into the area from the south. This will keep slight chance of
showers and thunderstorms from central to northeast OR. As
subsidence from the departing ridge decreases temperatures will drop
a little Saturday. A marine push will increase the winds
Sunday...especially through the eastern Columbia River Gorge and
lower Columbia Basin. The marine push should help clear out the
smoke over the region. The marine push will stabilize the atmosphere
along the Cascades and in the Columbia Basin though some showers and
thunderstorms will linger in the northeast OR mountains.

For Sunday night through Tuesday the extended models have been
flipping between a strong upper level low that will move southeast
from the Gulf of Alaska to off the WA coast and a more progressive
trough that will move across southern Canada with a cutoff slow
splitting off in CA. This increases the uncertainty for the end of
the forecast. Both solutions are significantly colder...so
temperatures will drop back to near or below normal by Monday. If
the strong low develops it will keep a chance of showers in WA and
OR as moisture and instability continue to advect through the area.
If the trough remains in Canada WA and OR will remain dry.
I did not change the current dry forecast.  Coonfield

&&

.AVIATION...00Z TAFs...VFR conditions with light winds and mostly
clear skies will persist through the next 24 hours. There will
continue to be widespread smoke and haze over the CWA which may
cause visibilities to drop below 6 miles at times. 76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  65  99  65 100 /   0   0   0  10
ALW  69 100  71 101 /   0   0   0   0
PSC  61 102  62 103 /   0   0   0   0
YKM  63 103  65 104 /   0   0   0  10
HRI  62 103  63 104 /   0   0   0   0
ELN  60 103  64 104 /   0   0   0  10
RDM  52  96  55  96 /   0   0  10  20
LGD  51  94  52  96 /   0   0   0  20
GCD  56  97  57  97 /   0   0  10  20
DLS  69 104  68 104 /   0   0   0  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory until 8 PM PDT Thursday for ORZ041-044.

WA...Heat Advisory until 8 PM PDT Thursday for WAZ024-026>028.

&&

90/76/76