Corvallis, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

423
FXUS66 KPQR 130330 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
830 PM PDT Tue Aug 12 2025

.UPDATE...Upwelling along the coast combined with a sea breeze
is increasing dense fog along the coast. Based on area web
cameras, observing fog along the beaches and Hwy 101 from
Lincoln City southward. Fog along the south Washington and
northern most Oregon Coast will be slower to develop and may be
more patchy until late in the evening. Wind speeds may be an
inhibiting factor to fog. -Muessle


&&

.SYNOPSIS...
Today remains hot, with afternoon highs approaching 100 degrees
across the interior valleys. Coastal areas continue to
experience mild conditions. A stronger onshore flow will develop
from Wednesday through Thursday, bringing a significant cooldown
of approximately 10 to 15 degrees. By Friday and into the
weekend, an approaching low pressure system in the northeast
Pacific is expected to deliver widespread rainfall and much
cooler temperatures across the region.

&&

.SHORT TERM...Now through Thursday Night...Wednesday ushers in
noticeable cooling as the upper-level ridge weakens due to an
approaching trough descending from western Canada. This will
enhance onshore flow, shifting winds to a west-northwesterly
direction and deepening the marine layer along the coast. While
temperatures will fall 10 to 15 degrees, conditions remain warm,
with afternoon highs expected in the mid to upper 80s within
interior valleys. The northern areas will experience the most
pronounced cooling. The HeatRisk will decrease to a "Minor"
level throughout the region, and overnight lows will become more
comfortable, generally ranging from the upper 50s to low 60s.

By Thursday, the initial trough will continue its eastward
movement, while a new upper-level trough originating from the
Gulf of Alaska begins moving into the Pacific Northwest. This
will maintain strong onshore flow with winds turning more
westerly. Afternoon highs on Thursday are projected to align
with or fall slightly below seasonal averages, reaching the
upper 70s to low 80s inland and the 60s near the coast. Rain
chances return late Thursday evening, with coastal areas from
northern Oregon into southern Washington possibly seeing light
rainfall accumulations around 0.05 to 0.10 inches, with a 10-30%
chance of exceeding those values. -Hall

.LONG TERM...Friday through Monday...
Rain chances increase beginning Friday as a weather system
approaches from the Gulf of Alaska, bringing cooler temperatures
and widespread precipitation across the region. This system
will likely persist through Saturday, with showers tapering off
into Sunday. Temperatures are expected to remain below normal
during this period. While widespread rain is probable, the exact
amounts and timing remain somewhat uncertain due to variations
in model forecasts. Thunderstorm activity is not favored but
cannot be completely ruled out, especially along the higher
terrain of the Cascades. By Sunday into Monday, the system will
weaken and move eastward, allowing drier and warmer conditions
to return.-Hall


&&

.AVIATION...VFR under mostly clear skies for inland locations
through the majority of the TAF period. There is a 20-30% chance
for MVFR conditions developing over inland locations. Satellite
imagery as well as ground observations are showing IFR/LIFR
conditions along the coast as the result of a broken fog/stratus
layer hugging the coast. There is a 45-60% chance that the lowered
flight conditions along the coast to improve towards IFR/MVFR
starting around 15-18Z Wednesday. Most locations maintain
west/northwest winds around 5-10 kt.

PDX AND APPROACHES...VFR with clear skies through the TAF period.
There is a 20-30% chance of MVFR conditions developing around 06Z
Thursday. Otherwise high confidence VFR conditions prevail.
-42

&&

.MARINE...Evening Update: Issued a Dense Fog Advisory for all
inner waters and the Columbia River Bar as visibilities could
fall towards 1 NM or less through at least Wednesday morning.
-42


Expect high pressure near the surface to maintain northerly winds
across the waters through Wednesday, breeziest during the
afternoon/evening hours and across the out waters - gusts to 15-25
knots. Seas around 7-9 ft at 9-10 seconds likely persists through
Wednesday as well with a fairly prominent northwesterly swell.
Given the choppy seas and aforementioned winds, Small Craft
Advisories will remain in effect across the outer waters through
1100 Wednesday.

Come Thursday we`ll see a noticeable pattern change as a low
pressure system in the northeast Pacific shifts winds more
southwesterly. The latest NBM guidance projects a 40-60% chance
for Small Craft conditions during a frontal passage during this
period, with the highest chances across the inner waters north of
Cape Foulweather and Columbia River Bar. Fortunately winds likely
lighten the latter half of the weekend into early next week as a
ridge to high pressure to attempt to rebuild overhead. -Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory from 1 AM to 11 AM PDT Wednesday for
     ORZ101>103.
     Heat Advisory until 10 PM PDT this evening for ORZ104-105-108.
     Extreme Heat Warning until 10 PM PDT this evening for
     ORZ109>125.
WA...Dense Fog Advisory from 1 AM to 11 AM PDT Wednesday for WAZ201.
     Heat Advisory until 10 PM PDT this evening for WAZ202-204-208.
     Extreme Heat Warning until 10 PM PDT this evening for
     WAZ205>207-209-210.
PZ...Dense Fog Advisory until 11 AM PDT Wednesday for PZZ210-
     251>253.
     Small Craft Advisory until 11 AM PDT Wednesday for PZZ271>273.
&&

$$

www.weather.gov/portland

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