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National Weather Service Area Forecast Discussion for Long Beach, WA USA

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Area Forecast Discussion
National Weather Service Portland, OR or
959 am pdt sat jul 22 2017

.synopsis...a weak frontal system will pass over nw washington today
with the tail end moving across extreme nw oregon and southwest
washington.  a weak upper trough will pass over washington on sunday
for a slight increase in onshore flow bringing a bit of cooling to
to the coast and willamette valley. an upper ridge will build over
our area on monday and tuesday for a warning trend. an upper level
low to our southwest will likely produce some thunderstorms in the
lane county cascade forecast zones sunday through tuesday before
moving eastward. increased onshore flow and moderate cooler temps
are expected for the second half of next week bringing temperatures
back to near normal.

&&

.short term...today through monday...weak frontal system has spread
some clouds to the extreme northwest corner of oregon and cowlitz
county this morning. don`t expect any precipitation from this front
as it passes by and  will lower pops in forecast for today.  850
temps about 4 degrees warmer today than yesterday which will result
in warmer conditions today reaching into the lower 90s in the
southern and central willamette valley today here onshoer flow along
the coast should continue to moderate temperatures there...but with
lots of sunshine. schneider

the low pres system to our north will move onshore tonight into
sunday, bringing the remnants of a cold front onto the pac nw coast.
this may deepen the marine layer just enough to assist in bringing
some patchy clouds into the northern willamette valley during the
morning, but otherwise expect clouds to again be limited to the coast
to start the day. the trough also drops temps aloft by a couple of
degrees. so expect sunday to be slightly cooler than today, but highs
should still make it into the mid to upper 80s for the interior
lowlands.

upper level heights increase again on mon. if any marine stratus
clouds form overnight sun into mon morning, they should remain
limited to the coast. the latest mos guidance is now suggesting that
mon will be at least as warm, if not a couple of degrees warmer, than
we see sat. so the interior lowlands have fcst highs into the low
90s, with a few mid 90s not out of the question.

a low pres system currently apparent on water vapor satellite near
36n/133w will slowly drift toward the northern calif coast this
weekend. the fcst models indicate that it will stall just offshore
later sun and remain nearly stationary for the next couple of days.
the southerly flow aloft ahead of this system will bring some
instability and modest mid-level moisture into southern or, leading
to the potential for thunderstorm activity. the potential is highest
to the south of our cwa, but the threat does appear to extend into
the lane county cascades and foothills. the fcst carries a slight
chance for thunder in these zones from sun afternoon through mon
night. pyle

.long term...monday night through friday...models have started coming
into better agreement with the handling of the upper low spinning off
the california coast early next week. both the ecmwf and gfs hold the
low offshore on monday and start lifting it towards central oregon on
tuesday which continues the thunder threat through tuesday. however,
the low is also continuing to track further south each run which is
precluding any thunder threat further north along the cascades. in
addition, it is worth noting that the beginning stages of the upper
low cutting off can be seen on water vapor just inside 140w, but the
moisture appears quite limited. this lends support for moisture being
a limiting factor and the nature of the storms being high based and
somewhat dry (hence the fire weather concern).

besides the thunder threat monday and tuesday along the central
oregon cascades, dry conditions will prevail with temperatures at or
slightly below normal.

the models suggest some degree of troughing along our coast during
the second half of next week though there are some differences
amongst the models. there should at least be some cooling back down
near normal. tolleson
&&

.aviation...cigs near kast will continue to lift this morning
and become vfr as a weak frontal system dissipates over the
forecast area. otherwise, expect predominately vfr conditions
under mostly clear skies through tonight. winds will increase
along the coast this afternoon with gusts to 25 kt possible at
konp after 18z and gusts to 20 kt at kast after 21z. winds in the
interior will increase this afternoon/evening with some gusts to
15 kt possible after 00z. mvfr conditions, with brief periods of
localized ifr cigs, look to redevelop along the coast after 06z
tonight. conditions in the interior will likely remain vfr the
next 24 hours. guidance continues to suggest the potential for
some mvfr cigs impacting the metro terminals after 12z sunday,
but confidence is low. expect any cigs that do develop to be
brief and lift by late sunday morning.

kpdx and approaches...predominately vfr the next 24 hours. expect
winds to increase this afternoon/evening, before subsiding late
tonight. guidance continues to show the potential for some mvfr
cigs developing over the columbia river early sunday morning, but
confidence is low on whether these cigs will impact the terminal.
/64

&&

.marine...winds and seas will start to increase this afternoon
for what will be a fairly prolonged period of gusty n winds
tonight through at least monday morning. a weak frontal system
will continue to dissipate near the mouth of the columbia river
this morning. this will allow high pressure to strengthen over
the ne pacific later today. meanwhile, hot weather over sw
oregon and nw california will help to strengthen a thermal trough
of low pressure. this will drive an increase in n winds this
afternoon, with gusts 25-30 kt expected across our southern
waters by sunset and spreading north into our northern waters
overnight tonight. the increasing n winds will result in steep
wind-driven seas later this afternoon and into tonight. winds
continue to increase sunday, with some models suggesting gale
force winds possible in our southern waters. gale force
northerlies are pretty rare in our waters, so given that the
stronger models continue to only show marginal gales will keep
the current small craft advisories for both winds and hazardous
seas. sca conditions may persist into tuesday so the current
advisories may need to be extended. eventually most models bring
an upper trough from the gulf of alaska closer to our waters,
which should eventually bring a decrease in winds/seas middle to
late next week. /64/weagle

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...small craft advisory from 8 pm this evening to 6 am pdt monday
     for coastal waters from cape shoalwater wa to cascade head
     or out 60 nm.

     small craft advisory from 4 pm this afternoon to 6 am pdt
     monday for coastal waters from cascade head or to florence
     or out 60 nm.

     small craft advisory for rough columbia river bar from 3 am to
     7 am pdt sunday.

&&

$$

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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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