556 
FXUS66 KPQR 161057
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
357 AM PDT Sun Oct 16 2022

.SYNOPSIS...Offshore flow persists this morning, leading to warm
temperatures in exposed areas while wind-sheltered valleys start out
the day much cooler. Inland areas north of roughly Salem will see
another day of record warmth today, while a switch to onshore flow
begins to cool off the remainder of the forecast area. Monday and
Tuesday will still be warmer than usual for mid-October, just not by
as much. Temperatures turn upward again Wednesday, potentially
challenging records again. This year's rainy season likely begins in
earnest Friday or Saturday as the first in a series of Pacific
frontal systems move across the Pac NW. This pattern change will
probably be the end of our summer-like warmth for the season.

&&

.SHORT TERM...Today through Tuesday...This morning's satellite
imagery continues to have a very summer-like look to it, with mostly
clear skies inland and solid marine stratus along the coast. With the
cloud cover and a return to onshore flow, Seaside and Tillamook will
certainly not pull off another day of near-90 degree warmth today. In
fact, either location will be lucky to reach 70 degrees today as warm
temperatures and thermal low pressure inland draw a robust onshore
flow into the Coast Range as today progresses. Eventually this
onshore push will work its way into the Cascades tonight and Monday,
leading to some cooling although temps will likely remain a few
degrees above seasonal norms. 

Meanwhile, dry and warm E-NE flow persists north and east of Salem. A
glance at the MSLP readings at 2 AM indicates a pressure minimum near
Salem, which is likely the boundary between warm and dry offshore
flow to the north and east and increasingly moist onshore flow to the
south and west. Latest PSL profilers and stratus pattern on satellite
indicate the marine layer is deeper to the south, with a 2000-2500 ft
marine layer at North Bend and a nascent 1000-1500 ft marine layer at
Astoria. Onshore flow has increased the past couple of hours at both
Eugene and Corvallis Airports, and stratus has pushed well into the
Coast Range gaps to their W-SW. It remains uncertain whether clouds
will actually form a ceiling in the southern Willamette Valley this
morning. But the strengthening onshore flow gives confidence that
models are correct in bringing several degrees of cooling to the
coast, Coast Range, and the south Willamette Valley versus
yesterday's record temperatures. Latest NBM v4.0 guidance suggests
only a 10% chance of Corvallis or Eugene reaching 80 degrees this
afternoon, compared to a 30% chance for Salem and a 90% chance across
the PDX metro.

Offshore flow is expected to slowly diminish in general today as
thermal low pressure migrates north and east. With offshore flow
decreasing, it seems unlikely anyone in our CWA will reach 90 degrees
today, but lowlands north and east of Salem should easily reach the
80s. Wind-sheltered valleys will likely hang onto their temperature
inversions longer today, causing temps to warm slower than yesterday.
Thus, places like the Upper Nehalem River valley may not be quite as
warm as yesterday. But the broader valleys should have no problem
warming up today in our well-mixed and dry environment. 

With high temperature records in the 76-83 deg F range for all our
lowland climate sites today, it appears likely we will see another
handful of records broken this afternoon. In fact, even at the stroke
of midnight, Troutdale was only 2 degrees shy of today's high
temperature record of 76 degrees, last set in 2015. With east winds
expected to continue gusting for at least a few hours after sunrise,
there is a chance Troutdale won't even get below 70 degrees this
morning. Even the NBM gives this a 10-20 percent chance of this
happening. Perhaps unsurprisingly, 100 percent of NBM members suggest
Troutdale will break their 76 deg F record high today. The NBM is
also bullish about Portland Airport breaking today's record high of
80 deg F, with roughly 70 percent of NBM members suggesting the
record will be achieved this afternoon (our forecast for PDX is 86
degrees today). Chances for record temperatures sharply decrease
southward from the Portland metro, with NBM probabilistic guidance
only showing a 7 percent chance of Salem reaching their record of 83
deg F and only a 5 percent chance of Eugene reaching their record of
81 deg F this afternoon. Suspect the chances are actually a little
higher than this, especially for Salem, but it does demonstrate how
cooler marine air is expected to filter in from the southwest today. 

The warm, dry, and breezy conditions lingering north of Salem are
also heightening wildfire concerns, and smoke produced by nearby
wildfires are also impacting air quality. The worst air quality
impacts have been around Oakridge as cool air drainage causes the
smoke to pool in that area each night, with air quality impacts
lingering well into each day in eastern Lane County. Smoke impacts
are not just limited to Oakridge; Air Quality Advisories have been
issued by our partnering agencies for much of SW Washington and NW
Oregon through Monday afternoon. There may be some brief improvement
in air quality Monday and Tuesday due to onshore flow and some marine
clouds, but it remains questionable whether or not the marine layer
will deepen enough to give slope/ridgetop portions of the Cedar Creek
Fire a break from the recent, persistent, dry conditions they have
generally been experiencing day and night for quite some time now.

Speaking of that onshore flow Monday and Tuesday, it should bring
inland temperatures down a bit, but temps will still be several
degrees above normal for all but possibly the coast. Both days should
feature the typical summertime pattern of coastal low clouds,
extending inland to some extent each night and morning, clearing back
to the coast by early each afternoon. Monday will probably be the
cloudier day of the two, but afternoon sunshine should push temps
into the 70s for our inland valleys both Monday and Tuesday. Models
have backed off a bit on drizzle potential Monday morning, but we
left a patchy drizzle mention along the coast due to our deepening
marine layer.  Weagle

.LONG TERM...Wednesday through Saturday...Some form of ridging is
very likely to return by midweek, as all 12z LREF clusters show by
Wednesday. This would return us to this month's familiar pattern of
strong ridging aloft, with dry air and temperatures turning 
warmer yet again for the latter half of the week. Assuming the 
PDX forecast highs around 86 deg F holds through this Sun, that 
would make 13 out of our first 16 days this October 80-degree 
days...more than doubling the previous record. Similar October
records have been broken at several of our climate sites, but not by
as much. There continues to be a chance PDX may tack on one or two
more 80-degree days this coming Wednesday and/or Thursday if 
some of the warmer forecasts come to fruition. We went ahead and
bumped Wednesday's temperature forecast upward, to around 81 deg F
for the Portland metro. That would be day number 14 out of 19 this
month with PDX reaching 80 degrees.

Longer range forecast models continue to show a strong signal toward
a pattern shift beginning Friday or Saturday, as some show the first
in a series of Pacific frontal systems moving onshore then. Given the
antecedent dry conditions, the strength and persistence of our ridge,
and some model disagreement on the strength of the first front, it
appears this first system will not be a soaker in terms of QPF.
However it does look like there is a high chance (70 to 80 percent,
based on latest cluster analyses) that subsequent systems will bring
more substantial rainfall beyond Saturday.  Weagle

&&

.FIRE WEATHER...Strong high pressure aloft will remain over the 
Pacific Northwest Sunday. The east wind will become more confined
to the west end of the Columbia River Gorge and south Washington
and north Oregon Cascades today. The 00Z NAM suggests the KTTD-
KDLS pressure difference will peak around -6 mb around 15Z this
morning and then weaken to -3 mb mid to late afternoon. Subsidence
inversions continue early this morning. These are especially
notable in the Lane County Cascades where 10Z RH values were
generally 20-30% on slopes and ridges. RH values for slopes and
ridges of the south Washington and north Oregon Cascades and 
foothills were a little better and will allow the Red Flag Warning
to end at 13Z. Wind will be more persistent in the south
Washington Cascades today, which will maintain a threat for Red
Flag wind/RH conditions through early Sunday evening. Light wind
and smoke pooling in valleys may lead to increasingly stagnant air
conditions in the Willamette Valley next week. Longer range 
models are in good agreement advertising a change to a more 
typical wetter and cooler Fall weather pattern towards next 
weekend.  Weishaar

&&

.AVIATION...12z TAFS: Coastal stratus has penetrated well into the
coastal valleys as of 10Z, especially between KTMK and K6S2.
Coastal areas will be primarily IFR through the morning and likely
into early afternoon along the central coast. Improvement to VFR
seems likely for the coast during the afternoon, but IFR to low-
end MVFR stratus will return by early Sunday evening. Most inland
areas to remain VFR through 12Z Monday. However, high-resolution
model guidance suggests IFR to low-end MVFR stratus will push up
the Columbia River to near KKLS between 06Z and 09Z Monday. In
addition, there is a 30-40 percent chance IFR to low-end MVFR
stratus reaches KEUG around sunrise and a higher probability early
Monday morning. Inland will continue to have haze or pockets of 
smoke from area wildfires. Additionally, KEUG and its proximity 
to the Cedar Creek fire still has a solid chance to see a few hour
period of reduced visibility from combined moisture and smoke. 
Finally, as surface winds weaken at KPDX and KHIO, will see LLWS 
again be a threat as winds around FL020-040 will still hover at 
35-40 kts tonight and well into tomorrow morning.

KPDX AND APPROACHES...VFR through 12Z Monday. Only concern is the
LLWS as described above. Weishaar

&&

.MARINE...Southerly surge in full swing early this morning.
Nighttime enhanced satellite imagery shows extensive stratus field
over the waters as of 10Z. Wind speeds from reporting buoys were
generally 10-15 kt with gusts up to 20 kt. These values fall in
line with the latest model guidance. South wind persists through
Monday, strongest Sunday afternoon and evening. Have capped wind
gusts just below small craft advisory thresholds, but this will
need to be closely monitored for potential highlights. 

Wind speeds diminish Monday, falling to 10 kt or less Monday
evening and continuing through Tuesday. North wind returns mid-
week, with possible small craft advisory gusts Wednesday
afternoon. Models in good agreement showing a change to a more
active pattern beginning late next week and continuing through the
weekend. A series of frontal systems are expected to sweep
through the waters during this period, with potential gusts up to
30 kt. 

Seas to remain in the 3-5 ft range through early next week but 
could increase to around 6-7 ft by Tuesday as an enhanced westerly
swell arrives in the coastal waters. Seas look to exceed 10 ft mid
to late next week. Weishaar


.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Red Flag Warning until 6 AM PDT early this morning for Mt. Hood 
     National Forest West of Cascade Crest-North Oregon Cascade 
     Foothills-Willamette National Forest.

WA...Red Flag Warning until 6 PM PDT this evening for Extreme South 
     Washington Cascades and Foothills.

PZ...None.

&&

$$

www.weather.gov/portland

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