Wildfire in Oregon, September 9 to 10, 2022

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1039 AM PDT Fri Sep 9 2022

Updated aviation and short-term sections.

.SYNOPSIS...A strong east wind event is on tap for today into
early Saturday. This will bring critical fire weather conditions,
above normal temperatures, and smoke and haze in various quantities
for different parts of the area. A southerly flow reversal Sunday
into Monday will lead to a strong onshore push which will replenish
moisture for lower elevations, along with a cooling trend next week.

&&

.SHORT TERM...Through Saturday night...The forecast in the short
term remains on track. An upper trough dropping out of central
Canada across the northern Rockies will drag surface high pressure
and cooler temps into NW Montana today, while the thermal trough in
western Oregon continues to expand northward. This will drive east
winds across the Cascades, foothills, and Coast Range, as well as
through terrain gaps, including the Columbia River Gorge. The
intensity of the east winds is forecast to increase this afternoon
as the pressure gradients tighten. As of 9 am Friday, the gradient
between North Bend, OR and Spokane, WA was 11.6 mb, up from roughly
6mb at 3 am. Winds have already turned easterly at Troutdale, though
not yet for many other locations throughout the Willamette Valley,
including PDX. The surface pressure difference is forecast to
increase to around 13 mb this afternoon, then to around 15-17 mb this
evening through early Saturday morning. Overall, HREF is
suggesting peak gusts for most areas will be 10-15mph less than they
were during the 2020 Labor Day event, so we'll continue to message
the possibility of gusts to around 25-35mph across much of the
Willamette Valley, 35-45mph near the Portland/Vancouver Metro, and
45-55mph across the high Cascades and exposed areas in the Foothills
this evening. Overnight tonight, the event will turn into more of a
classic gap flow event, where areas within and downwind (i.e., west)
of the gaps in the Cascades and Coast Range - most notably the
Columbia River Gorge - will experience their highest winds. The mean
of the HREF ensemble is suggesting gusts to 50+mph through the west
end of the Columbia River Gorge tonight, which seems reasonable
given the forecast maximum pressure difference of roughly 8mb from
Astoria to the Dalles for early Saturday morning.

The east winds will also bring warm and dry conditions to the area.
Temperatures are expected to be much warmer than normal today and
Saturday, with highs ranging from the 80s near the coast to the 90s
inland. There are also concerns for smoke advection from ongoing
wildfires in eastern Oregon and Washington, as well as from the
Cedar Creek Fire. Skies will be hazy with some areas possibly seeing
near surface smoke, especially in the southern Willamette Valley.
Overnight tonight into Saturday, surface low pressure will drift
offshore from the southern Oregon coast. Models also suggest the
thermal trough moves toward the Cascades Saturday afternoon, which
would cause winds to shift more onshore, mainly into southern
portions of the forecast area. By Saturday evening, the surface low
is forecast to be offshore west of Newport, OR. A southerly wind
reversal will bring increasing clouds late Saturday night.
-Bumgardner/DH

.LONG TERM...Sunday through Thursday...The surface low offshore will
continue to drift northward, bringing moist, onshore flow on Sunday.
This should replenish moisture levels somewhat for low elevation
locations for the start of next week. Sunday night into Monday there
will be a chance for drizzle along the coast and the Cascades as the
marine layer deepens with the approach of an upper trough which the
bulk of the ensemble thinks will pass just to our northwest.

Further out in the extended period, cluster analysis suggests little
uncertainty in the overall upper pattern with a slow approaching
trough from the west and the ridge gradually becoming less amplified
and shifting eastward through the work week. Both the EPS and GEFS
have many members that suggest precipitation at PDX by late week. In
addition, the ensemble is cooler next week overall; NBM suggests the
10th to 90th percentile maximum temperature range at PDX spans 73 to
82 for both Tuesday and Wednesday, which would put us close to our
average high of 78 degrees. DH/Bumgardner

&&

.FIRE...Expect a quick transition to offshore flow to commence this
evening as high pressure builds overhead and another disturbance
dives out of western Canada into the upper trough over ID/MT. East-
northeast winds will begin to increase by late evening over the OR
Casacdes, contributing to poor overnight recoveries as RH values
only climb into the 30s overnight. Still thinking inversions will
keep winds out of the inland valleys until Friday morning, but winds
will then quickly expand westward to the coast during the day on
Friday as the surface pressure gradient tightens in response to
strengthening low pressure along the coast and high pressure in the
Columbia River Basin. Red Flag warnings thus remain on track with
respect to timing and forecast details. Expect winds to peak Friday
night into early Saturday with some gusts to 50 mph over exposed
terrain in the Cascades, with 40-45 mph gusts in the Columbia River
Gorge favored terrain in the Coast Range. Expecting gusts around 35
mph in the Willamette Valley, but can't rule out a few gusts
approaching 40 mph. This will coincide with minimum RH values in the
teens across most of the area, with poor overnight recoveries,
especially in the higher terrain.

Winds should diminish relatively quickly on Saturday night as
another trough approaches offshore and the gradient weakens. This
will yield improving although still relatively dry conditions for
Sunday, with onshore flow pointing to more seasonable temperatures
and less dry conditions going into next week. Finally, there is
still a hint that the remnants of a tropical storm will approach the
area early next week, with a resulting slight chance of
thunderstorms sometime early next week. Confidence in this scenario
remains low at this time. /CB

&&

.AVIATION...18Z TAFs: Easterly winds are beginning to intensify
along the Cascades, and east-west aligned terrain like the
Columbia River Gorge. Satellite imagery shows widespread smoke
from the Cedar Creek Fire pushing eastward over the southern
Willamette Valley including KEUG. Based on the flow, could see
dense smoke just south of the terminal, but cannot rule out
diminished visibilities in the afternoon. This will greatly
depend on fire behavior. Most likely, the smoke will remain
elevated over the airport. Elsewhere, will likely see some smoke
aloft or haze due to nearby fires, but not expected to be nearly
as much. Through the day will see strong easterly winds around
35-40 kt along the Cascades and around 4000 ft. Could see some
eddies forming on the leeward side of the mountains due to
downsloping and warming, although confidence is low.

Easterly winds will strengthen downstream of the Columbia River
Gorge at KTTD and Coast Range gaps such as KTMK and KAST through
06-09z Saturday before gradually weakening thereafter.

For detailed Pac NW aviation weather information, go online to:
https://weather.gov/zse

KPDX AND APPROACHES...Offshore flow will bring VFR conditions
through 12Z Saturday. There is a 75% chance that easterly wind
gusts remain approximately less than or equal to 30 kt. If
downsloping or channeling occurs, could see isolated gusts
stronger than that. The strongest gusts should occur through 01Z
Saturday.
		  -Muessle/Neuman

&&

.MARINE...Offshore flow will result in gusty northeast to easterly
winds across the waters through early Saturday. A surface low
pressure will shift northwestward across the northeast Pacific
Saturday night into Sunday and result in southerly winds spreading
northward across the waters during that time. Expect solid Small
Craft Advisory level southerly winds gusts of at least 25 kt and
steeper seas during that time.

The aforementioned low pressure will gradually fill and shift back
towards the waters early next week. This will result in weakening
winds and lowering seas across the waters early next week. Surface
high pressure will gradually establish itself back across the
northeast Pacific towards the latter half of next week, which will
bring a return to northerly winds across the waters. /Neuman

For information about upcoming marine zone changes, go online to:
https://www.weather.gov/pqr/marinezone

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Red Flag Warning until 8 PM PDT Saturday for Central Oregon
     Coast-North Oregon Coast.

     Red Flag Warning until 11 PM PDT Saturday for East Slopes of the

     Central Oregon Coast Range-North Oregon Coast Range-
     Willamette Valley.

     Red Flag Warning until 11 PM PDT Saturday for Central Oregon
     Cascade Foothills-Mt. Hood National Forest West of Cascade
     Crest-North Oregon Cascade Foothills-Willamette National
     Forest.

WA...Red Flag Warning until 8 PM PDT Saturday for South Washington
     Coast and West Willapa Hills.

     Red Flag Warning until 11 PM PDT Saturday for Clark County
     Lowlands-East Willapa Hills-Eastern Gifford Pinchot
     National Forest Mt Adams Ranger District-Extreme South
     Washington Cascades and Foothills.

PZ...Small Craft Advisory until 9 AM PDT Saturday for Coastal waters
     from Cape Shoalwater WA to Cascade Head OR out 10 nm-Waters
     from Cascade Head to Florence OR from 10 to 60 nm.

     Small Craft Advisory until 3 AM PDT Saturday for Coastal waters
     from Cascade Head to Florence OR out 10 nm.

     Small Craft Advisory until 3 PM PDT Saturday for Waters from
     Cape Shoalwater WA to Cascade Head OR from 10 to 60 nm.
&&

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland