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fxus66 kpqr 271608 aaa 

Area forecast discussion
National Weather Service Portland or
906 am PDT Tue Jun 27 2017

Synopsis...dry northwesterly flow across the region persists with
broad upper level high pressure over the eastern Pacific. A ridge
moves across the Pacific northwest later this week, for slightly
warmer temperatures and less morning clouds across the region. A few
upper level disturbances in westerly flow may deepen the marine
layer later in the weekend, but overall seasonable weather is
expected through early next week.


Short through Friday...satellite, surface, and pilot
reports show western valleys under relatively thick marine stratus
layer this morning. Sle raob and pireps indicate tops between
4400-4800 feet, which is thick enough to likely persist into the
early afternoon. Expect breakout to mostly sunny skies around 21z.
Wednesday brings a a very similar day, although perhaps morning
clouds burning off an hour or two earlier. Remainder of the
discussion is unchanged. Drb

For the next few days, expect little change to the general pattern,
as a broad upper level ridge remains in place across the far
northeastern Pacific and into the Pacific northwest. This will
maintain the trend of morning clouds giving way to afternoon sunshine
and will maintain temperatures close to normals.

By Thursday, the offshore ridge migrates a bit closer to the region,
which will weaken the onshore surface pressure gradients. This will
ease the strength of the marine push for less widespread clouds and
somewhat warmer temperatures Thursday and Friday. Expect afternoon
highs in the lower 80s across the interior lowlands and in the mid
60s along the coast. Cullen

Long term...Friday night through Tuesday...weak onshore low-level
flow continues over the weekend, maintaining cool and generally
cloudy conditions along the coast. Expect that the onshore gradient
will be insufficient for widespread marine stratus intrusion into the
interior. Thus, abundant sunshine and a slightly warmer air mass will
push afternoon temperatures into the lower to mid 80s across the
Willamette Valley. There is general agreement among the model
guidance that a series of shortwave disturbances will track into
southern British Columbia or western Washington over the weekend and
early next week. The first is expected to arrive late Saturday or
early Sunday, though some differences remain with respect to the
strength and placement of the impulse. Nevertheless, expect that it
will be close enough to the forecast area to bring a stronger onshore
gradient, more widespread cloud cover, slightly cooler temperatures,
and perhaps some light precipitation to the region. The subsequent
shortwave likely follows a similar track and moves into the Pacific
northwest around Monday. Therefore, expect little change, with rather
seasonable temperatures and morning clouds giving way to afternoon
sun for the extended Holiday weekend. Cullen


Aviation...marine stratus is deeper today than what was observed
24 hours ago and there is widespread MVFR this morning. A pilot weather report
over ksle early this morning reported a stratus thickness around
2600 feet, which will result in a later inland clearing today.
Expect the Willamette Valley to clear around 21 or 22z (mid
afternoon). With persistent onshore winds and extensive stratus
offshore do not think the coast will clear today or tonight.
Models hint that the cigs will lower to under 1000 feet along
the coast tonight. A shortwave upper trough moving over the area
tonight will maintain a deep marine layer with MVFR marine
stratus moving inland into the Willamette Valley early Wednesday

Kpdx and approaches...based from a ksle pilot weather report think MVFR cigs
will lift to VFR between 20 and 22z (mid afternoon), with sky clear by
00z Wednesday (late this afternoon). Marine stratus will return
MVFR cigs very early Wednesday morning (11-13z). ~Tj


Marine...a persistent surface pressure pattern with high
pressure over the NE Pacific and a thermal low in northern California
will result in little changes to the overall marine weather for
the rest of this week and into the weekend. North-northwest winds will
mostly remain below 25 kt, although there will be a few gusts
around 25 kt in the waters beyond 20 nm this afternoon and

A combination of wind wave and fresh swell will create choppy
seas with heights 5 to 8 feet and dominant periods around 8
seconds today and Wednesday. There is also a very small long-
period (~14 second) S-SW swell. A strong Ebb Wednesday morning
may steepen the seas nearshore (0-5 nm) a few hours around the
845 am Ebb. A weak low moving across the Gulf of Alaska Wednesday
night and Thursday will increase wave periods to around 10
seconds beginning early Thursday. ~Tj


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for rough Columbia River bar from 8 am to
11 am PDT Wednesday.



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