543
FXUS66 KPQR 072000
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
100 PM PDT Mon Sep 7 2026

.SYNOPSIS...Drier and warmer conditions persist through Thursday
with temperatures gradually warming and peaking on Wednesday
with the development of low-level offshore flow. The forecast
becomes more uncertain Friday into Sunday, with the potential
for weather conditions to range anywhere from cool and showery
to warm and dry depending on the evolution of the large scale
weather pattern.

&&

.DISCUSSION...Tonight through Sunday...Confidence remains high
that dry and warm weather returns to the region through at least
the middle of this week. Model ensembles are in good agreement
that the upper level synoptic pattern will develop into a col
over the western portion of CONUS. A col also referred to as a
"saddle point", is formed when there is a set of lows and a set
of highs, that are in opposition to each other and results in
rather benign weather for locations near the center or peak of
the col. For our region, models have us on the eastern portion,
which will enable the upper level high over the Great Basin to
exert a little more influence in comparison to the other synoptic
features. As the Great Basin high develops it will induce a
weak, surface thermal trough that will build from northern
California into western Oregon, which will result in weak
offshore flow. Also, this will result in daytime highs warming
in the upper 70s to mid 80s for inland valleys, upper 60s to
upper 70s for the coast and lows 70s to low 80s for the
Cascades, with the warmest temperatures expected on Wednesday.
Thursday as well looks to remain warm and dry, but daytime highs
are expected to be around 5-10 degrees cooler than Wednesday.

Looking towards Friday and into the weekend, confidence in a
cooler pattern developing has increased. WPC 500 mb clusters
show around a 70% probability of a Canadian low dropping into
the Pac NW, while the other 30% cut off the Canadian low and
hold it in the northeast Pacific. Either solution will bring
cooler temperatures to the are, with the more favored solutions
bringing rain back into the forecast. Sill, even when looking at
the favored solutions, uncertainty remains as to the strength,
timing and location of the low. As such, ensembles are bringing
cooler conditions back to the Pac NW for the latter part of the
week and into the weekend. Deterministic, daytime highs for
Friday through Sunday are in the mid 60s to mid 70s for inland
valleys, upper 50s to upper 60s for the coast and upper 50s to
upper 60s for the Cascades. However, it should be noted that
daytime high temperature spreads from the 25th to the 75th
percentile are around 5-10 degrees with the 10th to 90th spread
around 8-15 degrees. So, there remains a lot of uncertainty
with the forecast. The outcome will be highly dependent on how
deep the trough becomes and if it tracks into Washington and
Oregon or further to the east towards the Northern Plains, which
will also determine whether or not rain will return to the
area. As for rain, ensembles are pointing towards a more wetter
solution, but precipitation totals are not expected to resemble
what was observed last week. Current 48 hours totals ending 5
AM Monday is around 0.15-0.5 inches across most of the CWA, with
the higher values over the Cascades. Overall, conditions
through the middle of this week look to remain warm and dry.
Cooler and wetter conditions are favored to return for the
latter part of this week and into the weekend, but that doesn`t
mean that those conditions are guaranteed. /42-03

&&

.AVIATION...Through 18Z Tuesday...Upper level troughing remains
over the region today with northwest flow aloft. Mostly dry
conditions expected as morning stratus is expected to become more
scattered by 19-20z this afternoon. As of 17z, a few terminals are
still reporting MVFR to IFR CIGs, including KUAO and KEUG. Expect
predominately VFR conditions returning after 20z and continuing
into the evening hours. Higher pressure begins to build across the
area tonight into Tuesday morning. Guidance suggests there is
around a 40-50% chance for stratus or fog to deteriorate
conditions at the coast after 11-12z Tuesday. Expect generally
light and variable winds at most terminals through the TAF period,
with the exception of northwest winds around 8 kt at coastal
terminals during the afternoon.

KPDX AND APPROACHES...Expect VFR conditions to persist as skies
gradually clear this afternoon. Light and variable winds becoming
northwest around 4-6 kt this afternoon. /DH

&&

.MARINE...High pressure offshore will maintain predominately
northerly winds across the coastal waters through the week. A
strengthening pressure gradient on Tuesday will bring stronger
northerlies with gusts up to 25 kt as there is an 80% chance of
wind gusts exceeding 21 kt by Tuesday evening. As a result, Small
Craft Advisories have been issued from 11 AM Tuesday to 6 AM
Wednesday for the outer coastal waters south of Cape Falcon, and
from 2 PM to 12 PM Tuesday for all other coastal waters. Breezy
winds continue through Thursday, but should remain 20 kt or less.
Seas of around 4 ft with a dominant northwest swell at 10-12
seconds will gradually build to around 6 ft late Tuesday as wind
chop increases with the northerly winds. A weak low pressure
system is expected to approach the coastal waters late Friday into
Saturday. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM Tuesday to midnight PDT Tuesday
     night for PZZ210-251>253-271.

     Small Craft Advisory from 11 AM Tuesday to 6 AM PDT Wednesday
     for PZZ272-273.

&&

$$

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