Skip to main content.

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

628
fxus66 kpqr 300607
afdpqr

Area Forecast Discussion...update
National Weather Service Portland, OR or
1107 pm pdt tue sep 29 2020

updated marine discussion

.synopsis...high pressure over the region will maintain warm and dry
conditions for rest of this week. will also add some hazy smoky skies
as smoke from california drifts overhead. will see return of westerly
flow this weekend, bringing cooler temperatures along with more blue
skies as smoke gets pushed off to our east.


&&


.short term...tonight through friday...water vapor satellite imagery
continues to reveal a shortwave ridge over the pacific northwest,
but it is beginning to transition southeastward. this has allowed a
southerly wind reversal to begin blasting northward up the coast as
seen in nighttime microphysics goes-17 imagery this evening. the uw-
wrf seems to have this handled pretty well at the moment so leaned
on it heavily for sky cover over the next 12-24 hours. this led to a
notable increase in fog and low cloud coverage across our waters and
along the coast during this time. given the marine layer will be
deepening, also added a mention of patchy drizzle along the
immediate coastline as well.

given the weakening offshore flow across the region, the feed of
drier air and east to northeast winds into the region has decreased
significantly. this has led to temperatures generally a couple
degrees cooler than 24 hours ago at this time with dewpoints running
5-10f higher. as a result, areas of valley fog away from the mouth
of the columbia river gorge should begin to develop towards daybreak.

many noticed the smoke aloft pushing into the region this evening.
most of this smoke will remain aloft overnight, but some of it may
mix down to the surface as the boundary layer deepens on wednesday.
visibilities along the coast have dropped down in the 6-8 mile range
so some deterioration in air quality can be expected on wednesday,
but to what extent remains uncertain. nonetheless, it seems very
unlikely air quality will reach levels observed in the days
following the labor day fires.

otherwise, expect a continuation of warm temperatures inland, hazy
skies and dry weather to persist into thursday. a weak shortwave
trough approaching the pacific northwest beginning friday should
increase southwesterly flow aloft across the region and begin to move
some of the smoke and haze east of the region, but it will likely not
be suddenly better by the end of friday. /neuman


.long term...(friday night through tuesday)...guidance is starting to
show the upper level ridge over the west breaking down friday night
into saturday, with return of more westerly zonal flow. this will
bring cooler temperatures, and bit more in way of low level onshore
flow. but, still dry.

models show another ridge offshore to start next week. if this bears
out, then may have another bout of light to moderate offshore flow,
with warm and dry conditions. but, that will only be temporarily.
both ecmwf and gfs support flow becoming more progressive as go
deeper into next week. models do diverge by wed and thu, with some
runs showing rather wet and strong front arriving, with others show
clouds and dry, with deep low approaching on thu into fri. so,
confidence high in changes for next week, but low confidence in what
will really happen. as they say, stay tuned...       /rockey


&&


.aviation...high pressure remains over the region through the
week keep conditions mainly vfr. smoke from wildfires to the
south will continue to move north across the area tonight. keug
observers and pireps has smoke layer around 080-100. the smoke
should thin somewhat wed afternoon.  expect smoke to mainly
remain elevated, but some surface smoke is possible closer to
ca.

fog/stratus is moving up the coast and as of 04z it is just
offshore of cape arago. latest uw-wrf has it moving up the coast
overnight into wed am. so have high enough forecast confidence
to add ifr conditions to coastal taf. timing - should see it at
konp after 09z and near kast 14z wed. may last at konp well into
the afternoon, but kast and other areas inland from the beaches
should be vfr around 19z-21z. finally with relative humidity
higher in the valley may see some fog wed am.

refer to http://weather.gov/zse for detailed regional aviation
weather and hazard information.

kpdx and approaches...vfr conditions persist with light winds.
elevated smoke from wildfires to the south will bring hazy
conditions. /64

&&

.marine...a southerly stratus surge will bring gusty south winds
to the waters tonight, with gusts to 20 kt expected with the
initial surge. the southerly stratus surge will also bring dense
fog and patchy drizzle to the waters as well tonight. expect the
stratus deck and gusty south winds to move into the southern
waters after 11 pm pdt this evening, and after 2 am pdt tonight
for the northern waters. the gusty winds will diminish later
wednesday morning, between 6 and 8 am pdt. dense fog and patchy
drizzle will linger through late wednesday morning before
lifting.

otherwise, high pressure aloft will keep conditions rather
benign over the next several days with winds generally less than
15 kt. seas are currently around 6 ft this evening, but look to
fall to around 5 ft on wednesday. expect this pattern to repeat
every 24 hours or so through the weekend as seas build back to
around 8-9 ft before falling to around 5-6 ft a day later. tk/64

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...none.
&&

$$

interact with us via social media:
www.facebook.com/nwsportland
www.twitter.com/nwsportland

Information courtesy of the National Weather Service - NWS Portland...
Issuing Weather Forecast Discussion Homepage