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

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Area Forecast Discussion
National Weather Service Portland, OR or
205 pm pdt wed may 27 2020

.synopsis...high pressure will continue to persist through friday
morning. a strengthening low pressure system originating from the
eastern pacific, will push northward friday night through saturday
bringing rain and a slight chance for thunderstorms through much of
northwest oregon and southwest washington. weak high pressure once
again develops towards the end of the weekend.

&&

.short term...tonight through friday night...an established upper
level ridge will continue to stay anchored over the pacific nw
through friday. this upper level ridge will keep the area warm with
weak northerly winds through the end of the week. temperatures are
expected to warm into the low to upper 80s inland and mid 60s to mid
70s along the coast thursday. friday temperatures should cool
slightly with inland temperatures in the low to mid 80s and coastal
temperatures in the low to upper 60s.

friday afternoon into friday night, deterministic and ensemble models
are in good agreement that a vertically stacked low from the eastern
pacific will make landfall in northern california. as a result the
surface portion of the low looks to spread out, pushing the majority
of its moisture and energy towards the northeast. the cause for the
increase is diffluent flow aloft and increasing easterly flow
developing from 3000 to 5000 ft. this pattern will bring a slight
chance for thunderstorms along the cascades and with the easterly
flow present, thunder chances could push into the willamette valley.
model soundings are suggesting that the convection will be on the
elevated side, that means the thunderstorm chances could persist
into saturday. /42

.long term...saturday through wednesday...the low will continue to
push to the northeast through saturday, maintaining favorable
conditions for thunder through the night. sunday a more
southerly wind pattern develops, which will cut off the majority of
thunderstorm activity and transition to a stratiform rain
pattern that persist through sunday night. monday the models have
a large upper level trough descending over the cwa. models are in
agreement that this through will drop south, but differ on what
exactly will happen. some models are suggesting that the area will
maintain a somewhat wet patter, while others suggest slightly drier
conditions. as a result have leaned towards climatology as well as a
blended forecast for precipitation, this has resulted in maintaining
low to moderate pops across the cwa. models do agree that this trough
will return winds to a more northwesterly flow and cool temperatures
closer towards seasonal normals. /42


&&

.aviation...at 21z satellite imagery indicated clear skies
across the entire region, with the exception of some high, thin
clouds. vfr skc conditions at all taf sites through thu
afternoon. there is the chance for local lifr along the coast
near k6s2 12z-15z thu morning. light offshore flow develops this
evening and strengthens overnight. this will primarily impact
the south washington and north oregon coast and higher terrain as
well as the western columbia river gorge. the thermally-induced
surface trough is forecast to reside over the interior valleys
thu morning and then move to the cascades thu afternoon.

kpdx and approaches...vfr skc at the terminal and vicinity
through thu. northwesterly sea breeze should pick up between 23z
and 01z thu and then diminish by 06z thu. areas east of the
terminal toward kttd will likely see east wind 10-15 kt late
tonight through thu morning. weishaar

&&

.marine...northerly low-level flow will persist through friday.
a thermally-induced surface trough is expected along the north
california and south oregon coast 12z thu. this feature shifts
inland by thu afternoon. models in general agreement maintaining
15-20 kt north boundary layer wind speeds over the waters through
saturday. the 12z nam and gfs continue the trend of showing
strongest boundary layer wind speeds friday afternoon and
evening, despite the surface gradient becoming more west instead
of northwest to north. the current small craft advisory runs
through 10z thu. will likely need another advisory for thursday
afternoon through late evening, but will defer to the evening or
mid shift.

wind speeds diminish saturday afternoon as a southerly marine
surge occurs. wind backs to west saturday night and sunday, with
speeds easing to around 10 kt. northwest wind returns early next
week with 20-25 kt gusts possible late monday afternoon.

seas should hold in the 4 to 6 ft range through early thursday,
with a pre-dominant fresh swell or wind wave component. a west-
northwest swell will then push into the waters late thursday and
result in seas climbing to near 10 ft. weaker pressure gradients
across the waters should then result in winds and seas subsiding
over the weekend. latest guidance shows a 3-4 ft longer-period
southwest swell becoming the dominant feature sunday night.
weishaar

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...small craft advisory until 3 am pdt thursday for coastal waters
     from cape shoalwater wa to florence or out 60 nm.

&&

$$

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this discussion is for northwest oregon and southwest washington
from the cascade crest to 60 nm offshore. this area is commonly
referred to as the forecast area.

Information courtesy of the National Weather Service - NWS Portland...
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