572 
FXUS66 KPQR 162213
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
313 PM PDT Sun Oct 16 2022

.SYNOPSIS...Offshore flow persists through this evening but will
turn onshore late tonight into Monday as a front advances
towards the coast. Monday and Tuesday will still be warmer than
usual for mid- October, just not by as much. Temperatures turn 
upward again Wednesday as high pressure returns. 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. 

&&

.SHORT TERM /THROUGH TUESDAY/...Easterly flow persists this
afternoon north of Salem, with gusty winds lingering through the
Columbia River Gorge and the south Washington Cascades. Observed
gusts upwards of 30 mph occurred through the Gorge, and some of
the higher and more exposed terrain exceeded those values. 
Winds though are beginning the downward trend as a weak cold 
front advances towards the region. This cold front has already 
started to transition the winds in the central and southern 
Willamette Valley to the south west, and will eventually make 
it's way up to the northern portions of the forecast area by
early Monday. Humidity levels were slightly higher than 
previous days as the onshore flow did it's job in moistening 
the environment. Temperatures well above normal were observed, 
and near record breaking, if not record breaking, temperatures 
occurred - especially in the northern inland portion of the 
forecast area. 

Overnight the front will move closer to the coast, deepening the
cool moist layer. With some activation from the front, could 
see some drizzle along the coast and coast range, but not 
expecting any accumulation. If there is any, it will be minimal 
at best. The front will impact temperatures though as they are 
forecast to be cooler than the last several days, but still 
warmer than normal by a few degrees. While onshore flow 
generally equates to clouds in the fall, hi-resolution models 
are suggesting that most of the clouds will get bogged down by 
the coast range, and rather inland areas will still see some
sunshine. Some areas though may be the exception to this rule 
like Eugene, which will be influenced by the subsidence 
inversion forming overnight. 

By Tuesday though, much of the front will have exited the area,
and high pressure begins to build in once more. It will start
off fairly flat, but there is great consistence with models 
that this ridge will amplify through the day leading to warm, 
and dry conditions. In fact, the cluster of deterministic models
show widespread ridging at 500 mb, with little variation 
between outputs. East winds will return late Tuesday, but are 
not expected to be nearly as strong as they were this weekend.

-Muessle
 

.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


&&

.AVIATION...00z TAFS: VFR and mostly clear skies prevailing 
inland this afternoon, with marine stratus continuing to impact
coastal areas and adjacent valleys. Gusty east winds continue to
impact the Portland area terminals this afternoon, but those 
winds should gradually diminish through this evening, holding on
the longest at KTTD. Have noted an uptick in wildfire activity in
SW WA this afternoon, but that smoke is mostly being advected 
away from area terminals. Could still see a thin layer of smoke 
aloft in some locations, with no major flight impacts expected 
through the period. Marine stratus showing some signs of eroding 
as of 22z, which should produce a mix of VFR and MVFR cigs at the 
coastal terminals into this evening. Stratus will fill back in at 
the coast between 03-06z, with another night of IFR or low end 
MVFR expected from KAST to KNOP. Expect a southwest marine push 
into the Willamette Valley overnight, first impacting KEUG after 
06z but then making gradual northward progress up the I-5 
corridor. HREF probabilities give about a 40-50 chance for IFR or 
low end MVFR cigs to make it into the Portland metro terminals 
after 12z Mon. Could see cigs around FL010 through about 18z Mn 
before stratus starts to break up. 

KPDX AND APPROACHES...VFR expected through 12Z Monday, with
easterly winds diminishing by around 03z. Marine stratus push
expected to approach the terminal after 12z Mon, with guidance
giving about a 50 percent chance for low end MVFR and a 40 percent
chance for IFR cigs through 18z Mon.                       -CB

&&

.MARINE...Southerly breezes will remain around 10-15 kt through 
Monday as a trough passes well offshore and a weak front brushes 
the outer waters, with gusts peaking around 20 kt this evening.
Wind will diminish Monday evening and go light and variable
through early Tuesday as high pressure builds back overhead.
Expect northerlies to then take hold through the middle of the
week as high pressure migrates offshore and a thermal trough
develops along the south OR and northern CA coasts. Could see some
gusts approach advisory criteria by Wednesday, with the strongest
winds favoring the southern and central waters. Seas will remain
around 3 to 5 ft through early Tuesday but are expected to 
increase to around 6-7 ft during the middle of the week as an 
enhanced westerly swell arrives in the coastal waters. Seas will
continue to build into the 8-10 ft range by Thursday and Friday.
                                                          -CB 

&&

.FIRE WEATHER...The Red Flag Warning remains in effect for the
south Washington Cascades and foothills. Winds though are
beginning to ease, though some locations remain gusty. Winds
around 2500 ft are gusting to around 25 mph, and ridges seeing
upwards of 30 mph gusts. Humidity today did get low right during
the period of peak heating and winds letting up, however with
the front expected tonight and the wind shift that will occur,
will see conditions moisten. Fire growth risk still remains in
areas exposed to easterly winds, but those chances will diminish
as the winds become onshore tonight into Monday morning. 

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Red Flag Warning until 6 PM PDT this evening for WAZ660.
PZ...None.
&&

$$

www.weather.gov/portland

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