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

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Area Forecast Discussion
National Weather Service Portland, OR or
300 pm pdt sat jul 4 2020

.synopsis...an upper level trough will linger across the pacific
northwest for much of the next week. this will produce a continuation
of morning clouds, afternoon sunshine, a few chances of light rain
showers and near to below average temperatures.


&&


.short term...tonight through monday...water vapor satellite imagery
continues to reveal a broad longwave trough over the pacific
northwest. in addition, there is a distinct vort max and embedded
shortwave trough sliding eastward across the oregon today.
per the ksle sounding, slightly cooler 850mb temperatures have spread
across the area over the past 24 hours as a result. this helped to
break up marine clouds a bit faster than previous days and has also
allowed some shallow instability to develop over the coast range.
this in turn resulted in a few very light showers developing over
the coast range and willapa hills earlier today. expect what
few showers exist to diminish rapidly this evening.

between a weak surface low pressure off vancouver island slowly
approaching the region and building 500mb heights overnight, sunday
morning cloud cover may be slightly less than the past couple of
mornings. however, href guidance still suggests most of the lower
elevations of northwest oregon and southwest washington should see
clouds fill in. this seems reasonable given the surface high
pressure ridge axis appears likely to once again setup near the
lane/douglas county border. nonetheless, sunday looks to be the
warmest day in the next week with high temperatures warming into the
mid to upper 70s.

the next storm system to impact the region is currently over the gulf
of alaska. models are in good agreement it will drop southeastward
and brush the region on monday before forming a closed low near
vancouver, bc monday night. this should increase morning cloud
cover and result in high temperatures cooling at least a couple of
degrees on monday. in addition, there will be a slight increase in
the depth of the moisture so the chances of morning light
rain/drizzle should increase, particularly along the coast.

as the closed upper level low develops near vancouver, bc monday
night, models and their ensembles seem to be trending towards
sufficiently deep enough moisture and instability spreading
southeastward across the rest of the region to bring more widespread
chance for light rain showers late monday night into tuesday. rain
chances appear to be highest across southwest washington where most
locations should measure rain during this time while areas farther
south towards lane county will more than likely remain dry.
nonetheless, the increase in low level moisture and cooler 850mb
temperatures will likely result in tuesday being quite cool with
high temperatures struggling to reach 70f for interior
valleys. /neuman


.long term...tuesday night through saturday...models are in decent
agreement a longwave trough will persist across the pacific
northwest during the second half of next week and into next weekend.
it appears at least a couple weak shortwave troughs dropping
southeastward out of the gulf of alaska into the base of the main
upper level trough will at least brush the region. this will
maintain our recent weather of late where widespread morning clouds
should gradually give way to afternoon sunshine each day with high
temperatures topping out near to slightly below average for the
date. models and their ensembles indicate there is still a lot of
uncertainty on the timing and strength of these passing shortwave
troughs, though. the first appears likely to impact the area
sometime between wednesday and thursday night while another one may
skirt the region next weekend. given the uncertainty in the timing
and amplitude of the waves, continued to hold pops in the 10% to 40%
range for much of the extended. /neuman


&&


.aviation...inland vfr to persist through the rest of the day as
subsidence aloft increases and continues to clear out the valleys
low lying clouds. breezy conditions are expected this afternoon
as the sea breeze picks up between 00z and 03z, otherwise winds
will be fairly weak out of the northwest. the weak low near
vancouver island will start to shift toward the coast over night.
this will increase the chance for early morning clouds between
11 and 16z. these clouds will most likely track along the
foothills but have the potential to bring broken mvfr ceilings to
valley sites.

clouds along the western slopes of the coast range are slow to
dissipate. this has brought an intermittent mix of mvfr to ifr
ceilings at konp. however, vfr is still expected to be the
dominant criteria through the afternoon and into the early
evening. favorable conditions for ifr ceilings and possibly fog
along the coast after 05z tonight into early sunday morning as
upper level ridging builds.

kpdx and approaches...expect vfr conditions to continue through
the day and into tonight with weak northwesterly winds over the
next 24 hrs. there is a low possibility of broken mvfr ceilings
late tonight. -bp


&&


.marine...no changes to previous discussion. a weak low off
vancouver island and surface high pressure off the south oregon
and north california coast will continue over the waters. wind
speeds 10 kt or lower will persist through at least the middle of
next week.

wave heights continue around 5 ft consisting of a northwest swell
and a long period south swell. all model guidance show wave
heights in the 3 to 5 ft range for the next several days. models
continue to show low-amplitude long-period south swell through
early next week. long period swell, such as the 16 to 18 second
south swell this weekend, usually raises concern regarding
sneaker waves. however, current guidance indicates rather low
wave heights associated with the long-period swell mixed with a
2-3 ft shorter period west to northwest swell. this produces
combined wave heights 4 to 5 ft. -bp/mh


&&


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


&&


$$

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