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

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Area Forecast Discussion
National Weather Service Portland, OR or
930 am pdt thu sep 19 2019

.synopsis...today will be a relative break from the wet weather
across sw washington and nw oregon, with a mix of sun and clouds for
most of the forecast area. a weak disturbance may clip our northern
zones with some light rain later tonight into friday, then high
pressure should result in a dry and mild day saturday. the next
organized frontal system will spread another round of rain across
western wa/or sunday.

&&

.short term...today through saturday...no changes. previous
discussion follows. most of the showers have dissipated across sw
washington and nw oregon, though weak low-level convergence is
maintaining a few light showers in the oregon cascade foothills. as
of 130 am, skies had cleared across much of the tualatin valley and
western willamette valley, allowing for good radiational cooling and
some patchy fog. expect some cloudiness to linger much of the day,
though there will probably be increasing sunbreaks during the
afternoon as some drying/mixing occurs in the boundary layer.
depending on how much sun we get, lower elevations may approach 70
degrees this afternoon.

high clouds will begin to encroach on the region from the north,
reaching astoria and the willapa hills this afternoon then spreading
south across the forecast area as a weak frontal system approaches
tonight. most guidance suggests spotty light qpf as a weak occluding
front moves through later tonight and friday. 00z nam time-height
cross sections suggest a deep moist layer with plenty of mid- and
high-level clouds friday, so there probably won`t be much sunshine
and showers will likely continue into the afternoon hours. as a
result, expect most of the forecast area to stay in the 60s for highs
friday, with higher elevations staying in the 50s.

low-level moisture lingers into saturday, but high pressure should
result in a drier day with a bit more sunshine, especially south of
salem. cannot completely rule out a shower saturday due to the
lingering moisture, mainly over sw washington where the moist layer
will be a bit deeper. latest nbm forecast suggests highs in the lower
70s saturday, which seems reasonable. if clouds clear a little
earlier than expected, 850 mb temps near +10 deg c may support temps
in the mid 70s saturday afternoon...the best chance for this will be
south of salem. either way, with an organized frontal system expected
for sunday, it appears saturday will be the relatively drier day this
coming weekend.  weagle

.long term...saturday night through tuesday...no changes. previous
discussion follows. after a brief reprieve from the rain, yet
another long wave trough will advance towards the west coast
saturday night. this low will usher in an extensive amount of
moisture, increasing rainfall throughout much of northwest
oregon/southwest washington. this low and associated cold front are
fairly fast moving and rain should only persist through day on
sunday. behind the trough, a ridge moves in as high pressure builds
in the pacific on monday. skies are expected to clear out early
monday morning causing temperatures to drop slightly. this decrease
in temperature along with the residual moisture from the rain on
sunday will create an environment suitable for fog development in
valleys and along the coast. this will be something to watch over
the next couple of days. the high pressure is expected to persist
through the middle of the week keeping conditions drier, and
temperatures slightly warmer in the 60s and low 70s.

&&

.aviation...a wide range of conditions this morning across northwest
oregon and southwest washington, with widespred ifr and mvfr
conditions mainly in the valleys and along the coast, but areas of
vfr conditions and mostly clear skies. expect improving conditions
from 17z to 20z, with mostly vfr conditions this afternoon and early
evening. expect mvfr ceilings to return tonight between 02z and 10z
as clouds spread initially from the north coastal areas southeast
into the willamette valley. mvfr conditions are then likely to
persist past 18z friday.

kpdx and approaches...mvfr ceilings this morning expected to break
up between 18z and 21z, leaving vfr conditions that will last
through the afternoon and into the evening. after 06z to 09z mvfr
ceilings are expected to spread back into the region from the
northwest, and then persist past 18z friday.

&&

.marine...no changes. previous discussion follows. surface high pres
will remain over the waters through sat morning with nw to n wind 15
kt or less. models in good agreement showing the next cold front
moving into the outer zones late sat night, likely resulting in
small craft advisory level wind. the front pushes inland by late sun
morning. high pres returns late sun and holds through early next
week. may see northerly wind gusts to 20 kt at times sun through
tue.

seas have slowly lowered below 10 ft and have allowed the small
craft advisory for the outer zones to expire. wave heights will
continue to diminish over the next couple of days. seas may reach
10 ft again sun. longer range model guidance shows a northwest
fetch reaching the waters around the middle of next week. have
gone conservative for now, generally 9-12 ft, but enp guidance
shows a core of 15-20 ft seas reaching the washington waters.
weishaar

&&

.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.