944
FXUS66 KPQR 181041
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
341 AM PDT Sun Aug 18 2024

.SYNOPSIS...Showers will linger across the area this morning,
primarily west of I-5 as an offshore low pressure system moves
north along the coast. Can`t rule out a few rumbles of thunder
with this activity. Drier and sunnier conditions expected this
afternoon with highs in the 70s. Benign onshore flow then
expected to continue through much of the next week, with
occasional light shower activity and inland highs remaining in
the 70s.

&&

.DISCUSSION...Considerably quieter weather prevails across the
area early this Sunday morning as the heavier shower and
thunderstorm activity associated with a potent shortwave trough
has shifted well north into Washington and British Columbia.
Partial clearing in the wake of this activity has allowed patchy
and locally dense fog to form across much of the area given the
abundant low level moisture in place from yesterday and last
evening`s rainfall.

Meanwhile, a deep upper level low is still located just
offshore of the north Oregon Coast, and this will be the
catalyst for lingering shower activity across parts of the area
this morning. Already seeing some weak radar echos starting to
fill back in across the southern half of the area as of 3 AM
Sunday, and expect this trend to continue later into the morning
as another impulse rotating around the large scale trough
tracks northward across the region. The bulk of this morning`s
shower activity will be concentrated west of I-5, though a few
showers could drift farther east over the Willamette Valley at
times as well. Can`t rule out a few rumbles of thunder with this
activity, but certainly nothing like yesterday in terms of
coverage or intensity given much more meager moisture, lift, and
instability in place today. All told, additional rainfall
amounts should be limited to a tenth of an inch or less today
with locally higher amounts in thunderstorms. Expect any
lingering showers to be confined to northern coastal areas by
early afternoon as the upper low continues to drift northward
off the Washington Coast. This will yield dry conditions and
mostly sunny skies across most of the area this afternoon, with
highs in the upper 70s in the inland valleys.

Medium to long range guidance continues to point to fairly
benign, low impact weather for the week ahead as the Pacific
Northwest remains under the influence of upper level troughing
and onshore flow through next weekend. Generally expect inland
highs in the mid to upper 70s each day, with spotty shower
activity lingering over the area at times in proximity to the
trough. The large scale trough looks to be reinforced by another
upper low dropping south along the BC coast Wednesday night
into Thursday, which could bring increased shower coverage and
renewed thunderstorm chances mid to late week. Ensemble and
deterministic guidance then show fairly good agreement that the
trough will eventually evolve into a cutoff low centered over
northern California by next weekend. /CB

&&

.AVIATION...Satellite imagery and terminal observations as of
0930z Sun has been a mix of IFR/MVFR/VFR cigs/vis as post-
frontal clouds scatter across the area. Saturation at the surface
from rain yesterday evening has allowed for the development of
shallow fog and low stratus in some locations in the Willamette
Valley. Most inland terminals will be VFR this morning, but there
is still a 10-30% chance of fog reducing visibility below 1SM
through 18z Sun. Along the coast, expect IFR/MVFR marine stratus.

After 18z Sun, widespread VFR is expected with skies gradually
clearing by late morning/early afternoon. Expect
south/southwest winds to strengthen after 18z, with gusts up to
25 kt along the coast and 20 kt in the Willamette Valley. After
00z Mon, winds weaken below 10 kt. Could also see a return of
marine stratus along the coast Sunday evening as conditions cool
and moisten.

PDX AND APPROACHES...Predominately VFR thresholds through the TAF
period, with a 10-20% chance of LIFR fog until 16-17z Sun. Light
southeast winds this morning will strengthen after 18z Sun and
gust up to 20 kt. Winds will shift more southerly/southwesterly in
the afternoon and weaken below 10 kt.-Alviz

&&

.MARINE...Low pressure over the NE Pacific will bring marginal
small craft conditions to the waters between Cape Shoalwater, WA
and Cape Foulweather, OR. Expect southerly winds 15-20 kt with
gusts up to 25 kt. Therefore, a Small Craft Advisory has been
issued for those marine zones including the Columbia River Bar
from 11 AM to 8 PM today. In addition, a second Small Craft
Advisory was issued for the Columbia River Bar for early Monday
morning as a very strong ebb is expected. Seas will remain around
3 to 5 feet through the end of the week.-Alviz

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 11 AM this morning to 8 PM PDT this
     evening for PZZ210-251-252-271-272.

  Small Craft Advisory from 3 AM to 8 AM PDT Monday for PZZ210.

&&

$$

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