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

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Area Forecast Discussion
National Weather Service Portland, OR or
836 pm pdt sun oct 17 2021

.update...
with the frontal boundary now hung up in the coast range of oregon,
and the whole system weakening as it moves inland, concentrating its
energy south into northern california, areas of stratiform rain and
post frontal showers are weakening and moving trending south as well.
have adjusted the pops and additional expected qpf to be further
east, and decreasing them especially along the coast. by sunrise, the
precipitation should only be occurring mainly over the or cascades.
/kriederman

&&

.synopsis...a cold front continues to slowly push across the region
this evening. then, another break with dry weather for monday and
tuesday. active weather resumes by midweek, as a parade of fronts
will bring periods of rain for wed through sat.

&&

.short term...tonight through tuesday night...a cold front has
slowly been pushing inland today with steady rain along the coast
and into the coast range. rainfall amounts have been heaviest across
the northwest oregon coast where 0.5 to 0.75 inch of rain has been
observed. goes water vapor satellite imagery sunday afternoon shows
the upper level shortwave digging south toward the northern ca
coastline. as the upper low approaches, the main southerly jet will
continue to weaken over western oregon. the front will push further
inland this evening as rain spread across the valley and into the
cascades, but have trended rainfall amounts lower with most
locations picking up around 0.10 inch, and up to 0.25 inch across
the central or cascades. the upper level system will move east over
the great basin late tonight and monday leaving the region under
northwest flow aloft. diminishing showers will be possible through
monday morning, mainly along the cascades. could still see a some
accumulating snow showers along the passes above 4500 ft, but should
be limited to around 1-4 inches.

a high pressure ridge offshore will shift eastward into the pacific
northwest later on monday and into tuesday. this will maintain dry
and mild weather through tuesday evening. offshore flow will likely
increase later in the day as the next weather system approaches.
temperatures will likely warm into the lower to mid 60s while clouds
will increase overnight. /dh


.long term...wednesday through saturday...a very active fall weather
pattern is expected through the end of the week. a deep upper level
trough will swing through the northeast pacific before lifting across

the pacific nw late tuesday through wednesday. deterministic models
suggest a strong frontal system will approach the coast early
wednesday morning and spread rain inland through the day. ensemble
mean and nbm rainfall amounts do not look too impressive at the
moment, but could see some gusty winds with this front. the region
will remain under southerly flow through thursday ahead of another
strong low pressure system. this will keep temperatures rather
seasonable through mid-week. will also likely see periods of dry
weather between systems. expect another round of rain, with this
next possibly stronger front, later thursday into friday.
deterministic models continue to be in rather good agreement through
the end of the week into the weekend, continuing the parade of
fronts and plenty of moisture. ecmwf ensemble total qpf members
indicate around 2 to 3 inches of rainfall could be possible by the
end of the long term period. /dh

&&

.aviation...04z update: current observations show that the cold
front has moved onshore with coastal sites seeing northwesterly
winds, broken ceilings and scattered showers. the front is
somewhere along the coast range as inland observations are
showing southerly winds and light rain within the warm sector
continuing north. most hires models have the entire forecast area
under a northwesterly wind pattern by 06z. cloud cover below 030
ft will build up against the cascades keeping the foothills and
terminals on the east side of the willamette valley in mvfr
conditions through the night and into the early afternoon.
clearing behind the front will in increase the chance for fog
development for all other sites within the valley. widespread
vfr conditions should be expected by 21z monday.

for detailed regional pac nw aviation weather information, go
online to: https://weather.gov/zse

kpdx and approaches...predominantly vfr is expected through the
night. showers will linger until roughly 09z monday with broken
ceilings around 045 ft. cannot rule out dropping back to mvfr
criteria for brief periods through the night. -bmuhlestein

&&

.marine...a blustery northwest wind regime has developed over the
coastal waters in the wake of the front as it moves onshore this
afternoon. small craft advisories remains in effect for all
zones through midnight as 20-25 kt gusts should persist through
this evening, particularly south of tillamook head. pressure
gradient will slacken overnight as high pressure moves overhead,
with winds trending light and westerly through monday morning
before shifting to the south during the afternoon ahead of the
next front set to approach the region later tuesday into
wednesday. this front will be in the process of weakening as it
enters the waters on tuesday, but will still result in a period
of stronger southerly winds from tuesday into the middle of the
week. at minimum, a fresh set of advisories is probable by
tuesday afternoon. did not have enough confidence for a gale
watch at this time, but a period of gales cannot be ruled out
later on tuesday, particularly on the far western reaches of the
outer zones beyond 50 nm. expect periods of enhanced southerlies
to then persist through the end of the week as another front
moves through the waters thursday into friday.

meanwhile, seas will be dominated by a decaying westerly swell
through the beginning of the week as it subsides from around 8
feet this evening to 4-5 feet on tuesday. the next front will
bring an uptick in short period seas tuesday into wednesday,
contributing to increasingly rough seas through later in the week
as a fresh westerly swell arrives at around 9-12 feet thursday
into friday. /cb

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...small craft advisory until midnight pdt tonight for coastal
waters from cape shoalwater wa to florence or out 60 nm.

&&

$$