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000
FXUS66 KPQR 182234
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
230 PM PST Sun Nov 18 2018

.SYNOPSIS...Dry weather with mild days and cool nights will continue
through Tuesday as high pressure east of the Cascades brings offshore
flow. A return to a wet pattern will begin Wednesday as frontal
systems move into the region from the Pacific. This pattern will
bring valley rain and mountain snow to the area through the end of
the week. Snow levels will be down to pass levels in the Cascades
Thursday though Saturday.

&&

.SHORT TERM...Tonight through Wednesday...A dry offshore flow
will continue through Tuesday as a strong ridge of high pressure
slowly moves across the region. Persistent surface high pressure
over the Columbia basin will maintain a fairly strong offshore flow,
with PDX-DLS pressure gradient on the order of -7 to -8 mb, which is
a bit weaker than the gradients we had with the east wind event this
past week.

The continental dry air will tend to limit fog potential the next
few nights and mornings despite clear skies and light winds away
from the gorge. The easterly flow through the Gorge is expected to
cause some stratus redevelop in the central Gorge and up into the
Hood River Valley.

Models continue to show the upper ridge moving east Tue night and
Wed as an upper trough slowly approaches the coast. Models have
tended to slow the approach of the trough and surfae frontal system
from previou runs, which is typical for the initial system pushing
into an upper ridge. Time height moisture profiles with the initial
system Tue night through Wed night are less than impressive, with
predominantly mid and upper level moisture. Will hold off pops until
Wed morning given the slowing, and limit categorical pops to coast
and mountains, with likely pops in the inland valleys. With the cool
nighttime temps around Hood River expected to continue and the
threat of rain moving in Wed morning, will need to retain a chance
for some freezing rain then.

.LONG TERM...Wednesday night through Sunday...Models in a bit better
agreement with the system moving in Thursday than they were this
time yesterday. A more vigorous front expected to push inland late
Thu with deeper moisture, so expect a decent shot of rain as the
front moves in, followed by showers in a cool onshore flow through
Fri. Snow levels some down with the front Thu, lowering to Cascade
passes, with accumulating snows to follow. There remains a
possibility for strong winds along the coast with both the 12Z GFS
and EC solutions, although placement of the surface low continues to
vary with each model run.

Beyond Fri, models continue to diverge significantly in solutions,
with EC favoring ridging and drying, while GFS is initially wetter
and slower to develop an upper ridge. Will tend to back off some
more on pops through the weekend, but will retain low pops through
Sun given model uncertainties and relatively high climatological
pops.

&&

.AVIATION...VFR conditions continue across the region under clear
skies today with high pressure over the region. Meanwhile, breezy
east winds continue through the western gorge and extending out to
KTTD, but likely will not extend to any of the other Portland metro
area terminals today. Expect that low MVFR stratus will return to
portions of the central gorge and areas around K4S2 overnight. It is
possible that some shallow fog develops late in the south valley
around KEUG as wind eases and radiational cooling becomes more
efficient, but not enough confidence in restrictions developing to
include in TAF at this time.

PDX AND APPROACHES...VFR conditions through the period under clear
skies. Gusty east winds east of the terminal near KTTD, but winds
will be lighter at the terminal and may vary between east and
northwest at times. Cullen

&&

.MARINE...Weather conditions across the waters remain fairly
benign through the first half of this week as large-scale high
pressure remains over the coastal waters. This pattern will shift
more dramatically around midweek as a much more active pattern
begins to emerge. Expects high-end advisory strength gusts when the
first system arrives late Tuesday into Wednesday.
Meanwhile, seas will approach 10 feet with this front. A stronger
system arrives around Thursday, with the potential for solid gales
and seas well into the 15-20 ft range late Thursday through early
Friday. Will need to continue to evaluate model trends to see if
storm force gusts may even be possible with this second system. The
more active pattern looks to continue into next weekend, but
forecast models diverge rather quickly so confidence in details for
this time becomes much lower.   Cullen


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.

&&

$$

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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the forecast area.