609
FXUS66 KPQR 031755
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1055 AM PDT Sun Aug 3 2025

Updated aviation discussion.

.SYNOPSIS...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 late
Wednesday into Thursday, however uncertainty is high regarding
exact rain amounts, if any rain falls at all. A warming trend
appears likely next weekend as high pressure builds over the
region, however uncertainty is high regarding how hot
temperatures may reach.

&&

.SHORT TERM...Today through Tuesday...Water vapor satellite imagery
early Sunday morning shows a shortwave trough extending from a low
pressure system in the eastern Gulf of Alaska and pushing east
toward the northern US west coast. This should bring increasing
clouds across the area with slightly cooler temperatures. Expect
highs this afternoon to warm into the mid to upper 70s, except 60s
along the coast. As the trough axis approaches the coast late Sunday
afternoon, convection is likely to initiate east of the Cascades.
That said, there remains around a 20% chance of an isolated
thunderstorm along the Cascade crest in Lane County.

With cooler air lingering across the area, combined with onshore
flow on Monday, expect similarly mild conditions with near normal to
slightly below average temperatures. Expect morning cloud cover over
the coast, SW Washington and the Portland metro with mostly clear
skies across the southern half of the Willamette Valley. Morning
clouds to the north should scatter out in the afternoon, but may
linger through much of the day for portions of southwest WA.

Onshore flow continues into Tuesday with weak troughing aloft. A
weak front moving over the coastal waters on Tuesday approaches the
coast later in the day, bringing increasing clouds and a 10-30%
chance of light rain along the northern coast. Temperatures inland
expected to be a few degrees warmer than Monday, but still near to
slightly below normal.  /DH


.LONG TERM...Wednesday through Saturday...Models and their ensembles
showing better agreement of slightly deeper trough moving over the
Pacific NW on Wednesday. This brings higher confidence to some
widespread rainfall through Wed night, as NBM probabilities have
increased to around 40-60% for the coast, and 25-50% inland, highest
across southwest WA and areas north of Salem. Suspect that still may
be a bit low. Instability may also increase Wed afternoon, with
enough sun and depending on timing of the upper shortwave trough.
Will maintain the 15% chance of thunder across northern portions of
the forecast area. Probabilities for at least 0.25 inches of rain or
more have increased to between 20-40%. Could see some lingering
showers into Thursday, while afternoon temperatures persist in the
upper 70s to lower 80s.

By the end of the week, WPC clusters are showing a general trend
toward upper level ridging building over the eastern Pacific
bringing warmer temperatures to the region next weekend. While
confidence is high temperatures will be trending warmer, confidence
is low regarding exact temperatures as model spread remains large.
The NBM 1D Viewer highlights this well for high temperatures,
suggesting highs could range anywhere from the mid 80s to lower
100s. If the ridge is able to nudge eastward over the PacNW, could
see a couple hot days, as the NBM maintains a 30-50% chance of highs
exceeding 100 degrees next Sunday into Monday. But after that,
indications are for a short lived event as temps trend cooler. DH/TK

&&

.AVIATION...Stratus has developed across most of NW Oregon and SW
Washington west of the Cascades Sunday morning. Expect flight levels
to bounce between high end MVFR (FL025) and low end VFR (FL040)
before lifting to prevailing VFR between 19-21z Sunday.
The main exception is the coast south of KTMK is VFR. MVFR/IFR
ceilings are expected to redevelop along the coast north of KTMK
after 03z Monday, spreading south along the coast by 10-12z Monday.
There`s a 40-70% chance of MVFR ceilings redeveloping inland between
10-14z Monday, lingering through 18-21z Monday. Winds remain north
to northwest, increasing to around 8-12 kts from 21z Sunday to 06z
Monday.

PDX AND APPROACHES...Brief high end MVFR/low end VFR (FL025-045)
through 20z Sunday, then becoming prevailing VFR. There`s a 50-70%
chance of MVFR ceilings redeveloping between 10-14z Monday,
dissipating by 18-20z Monday. Expect northwesterly winds under 10 kt
through the period. -HEC

&&

.MARINE...Minimal change in the forecast as a persistent pattern
will maintain relatively calm seas. Seas remain 3 to 5 feet
through the week and into next weekend. Winds will be northwesterly
10-15 kt with gusts as high as 20 kt along the coast and the far
outer waters through Monday. Due to the northerly flow, the inner
waters will see the gustier conditions though will remain just
below critical criteria.

On Tuesday, a low pressure system drops south into Haida Gwaii,
bringing southerly winds over the waters. Within the inner waters
there will once again be an increase, but gusts will be flirting
with Small Craft Advisory levels. Wind waves will react and thus
bring combined seas to 4-6 ft at 10-12 seconds.
~Hall/Muessle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

$$

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