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National Weather Service Area Forecast Discussion for Seaside, OR USA

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Area Forecast Discussion
National Weather Service Portland, OR or
858 am pdt tue jul 25 2017

.synopsis...clouds will clear this afternoon for widespread sunshine
and slightly above normal temperatures. an upper low moving inland
across north california may trigger a couple of thunderstorms for the
lane county cascades this afternoon and evening. marine stratus will
fill in along the coast tonight, and move into the north  willamette
valley wednesday morning. a deeper marine push expected  wednesday
and thursday nights for near seasonal temperatures thursday and
friday. high pressure builds this weekend for a slight increase in
temperatures.

&&

.short term...today through thursday...made minor changes to sky
forecast in the short term, otherwise current forecast is on track. an
upper level low currently over the north california coast will slowly
move inland across north california today and tonight providing a
slight chance for thunderstorms across the lane county cascades. high
clouds associated with this low may stream over nw oregon at times,
but overall inland skies will be clear today.

there are some clouds along the coast and coastal valleys this
morning that should clear early this afternoon. satellite imagery
shows extensive marine clouds well offshore that should move into the
portland coastal waters this evening for clouds returning to  the
coast tonight. light northwest winds will move these clouds through
the lower columbia river valley into parts of the north willamette
valley (including the portland metro area) wednesday morning.
additionally, stratus may form over the southwest washington and
northwest oregon cascade foothills wednesday morning. ~tj

the remainder of the discussion is from the previous issuance (315
am)...the upper level low will move further onshore early wed, then
lift north and east into the interior pac nw wed night. this will
lead to the flow aloft becoming more westerly, effectively ending any
thunder threat west of the cascades. there should also be a bit more
of an inland stratus surge wed morning. expect at least northern
portions of the willamette valley to see some morning clouds. high
temps wed will cool around 5 deg over the lowlands.

as the upper low moves further inland wed night, expect a much deeper
marine surge thu morning, with clouds likely filling most of the
interior lowlands. morning clouds will give way to afternoon sunshine
over the interior, with clouds likely remaining through most of the
day at the coast. temps thu will be even cooler, with highs generally
in the low 80s for the lowlands. pyle

.long term...no changes. previous discussion follows...thursday night
through monday...onshore flow from a series of weak shortwave troughs
will continue through next week. this will maintain near normal
temperatures with low clouds at the coast most mornings. no chance of
precipitation or thunder during this time. bishop

&&

.aviation...vfr across the region except for areas of ifr along
the coastline and coastal river valleys. the inland ifr areas
will persist through about 17z, but last until 20z along the
coast. ifr to low-end mvfr cigs return to the central oregon
coast by 03z wed and to the north oregon and south washington
coast between 03z and 06z wed. models suggest a deeper inland
stratus penetration late tonight and wed morning.

kpdx and approaches...vfr with thin cirrus through at least 12z
wed. there is a chance that mvfr stratus reaches the terminal
around sunrise wed. weishaar

&&

.marine...wind over the outer waters generally beyond 30 nm
expected to continue gusting to about 25 kt through late tonight.
current small craft advisories look good. will need to monitor
seas for pzz250 and pzz255 for possible square-sea conditions.
latest report from buoy 029 came it at 5 ft with an 8 second
period. spectral guidance for buoy 029 shows seas generally 6 ft
through this evening then easing a bit more tonight and tue.

pzz255 and pzz275 may get close to small craft wind criteria
again wed afternoon. gfs indicates boundary wind speeds of 20 to
25 kt wed afternoon, which is slightly stronger than the nam.
wind speeds gradually diminish beyond wed with stronger onshore
flow that will result in a more dominant nw wind and a deeper
marine layer over the waters. seas ease to 4 ft or less wed and
hold at that level through the weekend. weishaar

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...small craft advisory until midnight pdt tonight for waters from
     cape shoalwater wa to cascade head or from 10 to 60 nm.

     small craft advisory for winds from 2 pm this afternoon to
     midnight pdt tonight for coastal waters from cape
     shoalwater wa to cascade head or out 10 nm.

     small craft advisory until 2 am pdt wednesday for waters from
     cascade head to florence or from 10 to 60 nm.

     small craft advisory from 2 pm this afternoon to 2 am pdt
     wednesday for coastal waters from cascade head to florence
     or out 10 nm.

     small craft advisory for rough columbia river bar until 9 am
     pdt this morning.
&&

$$

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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.

Information courtesy of the National Weather Service - NWS Portland...
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