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

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Area Forecast Discussion...updated
National Weather Service Portland, OR or
957 am pst wed nov 20 2019

updated aviation and marine discussion

.synopsis...high pressure over the region will result in benign
weather through the first half of the weekend before an increasingly
active and stormy weather pattern develops next week.


&&


.short term...today through saturday...water vapor satellite imagery
early this morning reveals a shortwave ridge over the northeast
pacific and a closed low pressure over california. models are in good
agreement the shortwave ridge will slowly bend over and shift across
the pacific northwest over the next 48 hours. this will bring a
multi-day stretch of dry weather to the region.

offshore pressure gradients will build later today into thursday,
which should result in increasing easterly winds through the columbia
river gorge. in addition, there should be enough of a northerly
pressure gradient across the region that air stagnation concerns
should be limited to nonexistent across the area today into thursday.

a weak and splitting shortwave trough will push towards the region
thursday into friday. this upper level storm system will drag a dying
low level front towards the region thursday night into friday. model
and ensemble guidance continue to suggest it will fall apart enough
before arriving to maintain a dry forecast. the main impact from this
storm system is that it will likely reduce offshore pressure
gradients enough that fog coverage should expand friday and saturday
mornings across the area. otherwise, expect high temperatures right
near average for the date with low temperatures near to below
freezing at night for many valley locations through saturday. /neuman


.long term...saturday night through wednesday...models and their
ensembles are in fair agreement a shortwave ridge will bend over the
pacific northwest and open the door for an increasingly zonal and
active weather pattern for the pacific northwest next week.
conditions should start off dry across the area saturday evening
before a dying front drop southeastward across the area saturday
night into sunday. some amplitude and timing differences still exist
during the saturday night and sunday timeframe so pops have generally
been held into the chance to likely categories for now.

models then generally agree a strong upper level jet will take aim at
the pacific northwest early next week. the operational gfs and ec
suggest a weak surface low pressure will develop and track towards
the pacific northwest. this would likely result in a wet and
potentially cool pattern with plenty of snow across the cascades
tuesday into wednesday. meanwhile, the gem suggests a much stronger
surface low pressure will track towards the region, which would
result in a considerably milder, windier and somewhat wet pattern for
the region. considering the spread in the gefs and ecs ensemble
systems, a variety of scenarios appear on the table tuesday into
wednesday so have opted towards trending the forecast towards a
middle of the road scenario as output by nbm guidance. /neuman


&&


.aviation...high pressure continues to build over the area
bringing predominately vfr conditions. ksle and areas south are
currently under ifr stratus but that should lift and scatter out
by 20z wednesday. winds will begin to turn offshore starting
around 20z wednesday, and continue through the forecast period.
an increasing pressure gradient between kttd and kdls will
develop through today. therefore, expect gusty winds near kttd
and towards the mouth of the columbia river gorge after 00z
thursday. patchy fog possible thursday morning under vfr cigs as
the offshore winds look to weaken during the overnight hours.

kpdx and approaches...vfr ceilings will dominate through
wednesday. winds will become offshore today and will continue through
thursday. east winds will increase around 00z thursday. patchy
fog possible thursday morning under vfr cigs. /42

&&

.marine...seas and winds are easing but slower than what models
are suggesting. therefore, have extended the small craft advisory
through at least wednesday afternoon for the inner and northern
outer waters, as seas have remained around 10 feet at 10
seconds. winds in zone pzz275 are expected to persist at around
10 to 15 kt with 25 kt gusts, also seas are remaining around 10
ft through at least tonight.

seas continue to fall today, but are also becoming more square. so
choppy seas are possible as they fall below 10 ft. high pressure
building over the waters will cause winds to ease towards the 10
to 15 kt range and seas to subside to the 6 ft range.

the next system is expected to move over the waters thursday
afternoon. over the last several days, this system has weakened
which leads to some lack of confidence in the track and
intensity. however, guidance is still forecasting seas to
increase quite drastically to 12 to 14 ft with a period of 15 to
18 seconds fri night into sat. conditions will again ease on sun
as zonal flow takes hold. -muessle /42

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...small craft advisory until 3 pm pst this afternoon for coastal
     waters from cape shoalwater wa to florence or out 10
     nm.waters from cape shoalwater wa to cascade head or from
     10 to 60 nm.

     small craft advisory until 4 am pst thursday for waters from
     cascade head to florence or from 10 to 60 nm.

&&


$$


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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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