593
FXUS66 KPQR 021002
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
302 AM PDT Sat Aug 2 2025

.SYNOPSIS...Near average temperatures expected today. General
troughing and increasing onshore flow will bring relatively cooler
temperatures Sunday through Thursday with increasing chances for
cloud cover, especially during the morning hours. Chances for
widespread rain increase Wednesday into Thursday, however
uncertainty is high regarding exact rain amounts, if any rain falls
at all. A warming trend appears likely into next weekend as high
pressure potentially builds over the region, however uncertainty is
high regarding how hot temperatures may reach.

&&

.SHORT TERM...Today through Monday...Very little change to the
overall pattern today, though marine stratus may bring a few low
clouds up the lower Columbia this morning. Expect clouds to give way
to mostly sunny skies by mid-day with temperatures again warming
into the 80s, along with a slight chance (10-20%) of thunderstorms
along the Cascade crest near the Willamette Pass eastward. Breezy
onshore winds return later in the afternoon.

Conditions trend cooler and cloudier on Sunday as a weak upper level
shortwave trough moves over the coastal waters and across the
Pacific Northwest late Sunday. Expect mid and high clouds to
increase from west to east by sunrise. The increasing cloud cover,
combined with cooler temperatures aloft, will support cooler
temperatures with daytime highs generally in the 70s, although if
skies clear somewhat, could see temps pushing back toward 80
degrees, especially through the southern and central Willamette
Valley. Sunday also features a 15-30% chance of showers over the
Oregon Cascades during the afternoon and evening hours. Depending on
how much instability resides, NBM maintains a slight (15%) chance of
thunderstorms near the crest of the Cascades in Lane County.

With cooler air lingering across the area, combined with onshore
flow on Monday, expect similarly mild conditions. Near to slightly
below average temperatures expected Monday with some lingering
clouds possible over northern portions of the forecast area.  /DH

.LONG TERM...Tuesday through Friday...Not much change to the long
term forecast. General low amplitude troughing with embedded upper
level shortwave trough will maintain onshore flow through at least
the middle of next week. Expect near to slightly below average
temperatures with a mix of sun and clouds each day. Could see the
marine layer deepen with around a 10-20% chance of light rain or
drizzle along the northern coast Tuesday, with increasing chances
(up to 40%) along much of the coast on Wednesday.

Models and their ensembles are showing increasing chances for more
widespread rain late Wednesday into Thursday with the possibility of
a weak low pressure system approaching the west coast. The NBM is
showing increasing chances (albeit still in the minority) of 24-hour
rainfall probabilities exceeding 0.25 inch of around 20-30%. Still,
there are around 50% of ensemble members that show no precipitation
at all.

By the end of the week, WPC clusters are showing a general trend
toward upper level ridging building over the eastern Pacific
bringing potential for warmer temperatures into next weekend. The
CPC does indicate there is a slight risk of extreme heat along the I-
5 corridor, beginning Saturday; while the NBM suggests there is
around a 30-50% chance of exceeding 100 degrees next Sunday through
the Willamette Valley.  /DH

&&

.AVIATION...Currently as of 09Z Saturday, LIFR/IFR conditions
persist along the coast and VFR conditions inland. These
conditions along the coast will likely persist until 17-18Z
Saturday, with chances for LIFR/IFR CIGs around 40-80% (lowest to
highest chances from north to south). By 18-19Z Saturday, could
see MVFR conditions as chances lower to 10-30% for IFR CIGs and
50-60% for MVFR CIGs. By 03-06Z Sunday, deteriorated conditions
begin to redevelop along the coast and will persist through the
rest of the TAF period (earliest to latest from south to north).
Otherwise, northwesterly winds will increase at coastal terminals
around 20Z Saturday to 03Z Sunday, with gusts 20 to 25 kt
expected.

Inland, terminals will stay VFR through most of the TAF period.
The only exception will be in the morning from 12Z to 18Z
Saturday, where coastal stratus may push up the Columbia River
and into KPDX, KHIO, KTTD, and KVUO. Additionally, coastal stratus
could push through the coastal gaps into KEUG. Model guidance
suggests a 20-30% chance for MVFR CIGs to develop at these inland
terminals during the aforementioned time. Considering current
observations of stratus at KKLS, the pattern looks on track for
conditions to briefly deteriorate at most inland terminals. The
only uncertainty will be if the cloud deck forms uniformly enough,
as yesterday morning observations were few and scattered around
FL015. Otherwise, expect northwesterly winds around 6 to 10 kt
with brief gusts to 18 kt possible at a few terminals between 00Z
and 08Z Sunday.

PDX AND APPROACHES...VFR conditions will persist through most of
the TAF period. Between 12Z and 18Z Saturday, could see
conditions deteriorate to MVFR at the terminal. Uncertain whether
the cloud deck will be more uniform (broken or overcast), as
yesterday was only few or scattered around FL015. While
probabilistic guidance suggests a 20-30% chance of MVFR CIGs,
deterministic guidance suggests CIGs will stay above FL030.
Otherwise, expect northwesterly winds 8 to 10 kt with gusts up to
18 kt between 00Z and 08Z Sunday.
~Hall

&&

.MARINE...Overall fairly calm conditions persist through the
weekend as an area of surface high pressure sits across the
waters. Northwest winds in the afternoon and evening hours will
occasionally gust up to 14-20 knots but Small Craft conditions are
not anticipated. Marine stratus is rather prolific this morning
and when considering the current pattern, morning stratus will
likely reoccur every morning through the weekend and into Monday.

Come Tuesday, an approaching surface trough brings about a
southerly wind shift across all waters for albeit with wind gusts
likely remaining below small craft conditions. Later in the week
guidance does hint at the potential arrival of a slightly stronger
trough which would push wind gusts closer to 21 knots - the NBM
suggests a 30-50% chance for Small Craft winds across the
southern waters by Friday.
~Hall/Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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