548
FXUS66 KPQR 060530
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1030 PM PDT Sun Apr 5 2026

.UPDATED AVIATION DISCUSSION.

.SYNOPSIS...Dry conditions will persist through Friday aside
from a chance of showers over the Oregon Cascades Wednesday
through Friday. High pressure will maintain well above normal
temperatures for this time of year through Monday. Onshore flow
returns Tuesday and Wednesday, bringing relatively cooler
temperatures. Trending a bit warmer again Thursday into Friday
with light offshore flow developing. Shower chances return to
most of NW OR and SW WA on Saturday.

&&

.DISCUSSION...Sunday through Saturday night...Satellite imagery
early Sunday afternoon shows a thin layer of high clouds moving
over NW OR and SW WA as high pressure and low-level offshore
flow remains in place. Easterly winds remain a bit breezy
through the western Columbia River Gorge into the Troutdale,
Washougal, and Camas areas with gusts up to 15-25 mph. Expect
easterly winds to ease late in the day as low-level offshore
flow weakens. Despite the high clouds in place today,
temperatures are still on track to warm well into the mid to
upper 70s across the interior lowlands and upper 60s to lower
70s at the coast. As of noon, many locations have already passed
the 70 degrees mark. Most locations within the Willamette
Valley and greater Portland/Vancouver metro have anywhere from a
10-30% chance of reaching 80 degrees or warmer this afternoon.
Although high pressure weakens a bit tomorrow with 850 mb
temperatures cooling slightly, high clouds will be dissipating.
Given a full day of sun, Monday is on track to be just as warm
as Sunday with similar probabilities of reaching 80 degrees. The
only exception is at the coast where the return of onshore flow
will bring relatively cooler temperatures compared to Sunday
with highs near 60 degrees. A few record high temperatures may
be tied or broken both today and Monday. It is not recommended
to cool off in local lakes and rivers as water temperatures are
currently frigid enough to result in cold water shock, which can
become life threatening.

A weak and dry cold front associated with a low pressure system
moving east through British Columbia is slated to move over the
region late Monday into Tuesday. Ahead of this, models are
showing upper level flow shifts westerly and a very subtle
upper shortwave associated with the front could cause enough
orographic lift for a 15-20% of isolated showers over the
southern Lane County Cascades Monday afternoon. However, better
chances will be east of the Cascade crest. Temperatures then
trend cooler Tuesday and Wednesday behind the front with dry
northwest flow aloft and relatively stronger low-level onshore
flow. The NBM depicts low model spread for temperatures both
days, suggesting high temperatures will likely wind up in the
low to mid 60s, except 55-60 degrees at the coast.

Mostly dry weather will persist through Friday except for over
the Oregon Cascades south of Clackamas County. Ensemble guidance
indicates the potential for wrap-around moisture from the south
associated with a low pressure system spinning off of the
northern California coast. This moisture could move far enough
north to produce shower chances each day, mainly in the late
morning through early evening hours. Potential frost chances are
now mainly limited to Wednesday morning. Probabilities for low
temperatures of 36 degrees or colder range between 10-25% over
the interior lowlands and inland coastal communities, except
1-5% in the Portland metro to the east of the West Hills, and
50-80% in the Upper Hood River Valley from Odell to Parkdale.
Anyone with sensitive outdoor vegetation that is susceptible to
frost damage should stay up- to-date on the temperature forecast
over the coming days and monitor for potential Frost
Advisories.

Model guidance continues the brief warming trend Thursday
through Friday due to potential shortwave ridging on the
northeast periphery of the aforementioned upper low. As such,
the deterministic NBM is suggesting highs in the upper 60s to
low 70s over the interior lowlands both days. NBM indicates a
40-60% chance of high temperatures of 70 degrees or higher each
day, except for a 65-80% chance for the Portland metro area.
This weak ridging is the main reason frost chances are
decreasing for Thursday and Friday mornings as it will also
cause slightly warmer overnight temperatures, generally in the
40s.

By next Saturday, the 500 mb cluster analysis of the GEFS, EPS,
and GEPS indicates two potential solutions in the pattern with
about a 50/50 chance for each. One solution keeps the pattern
similar to Thursday and Friday except with a weak trough
approaching the West Coast from the Pacific. This solution keeps
the area mostly dry with shower chances in the Cascades, though
temperatures are more likely to begin cooling towards normal
with the approach of a trough. The other solution suggests a
deeper trough impacting the PacNW and bringing increased rain
chances across the entire region sometime on Saturday. This
uncertainty has resulted in a 20-35% chance of rain showers west
of the Cascades and a 35-60% chance over the Cascades. Even if
showers do return Saturday, guidance suggests rain amounts will
be light with an 80-90% chance total rain amounts will be less
than 0.25 inch west of the Cascades and a 50-70% chance over the
Cascades. -03/23

&&

.AVIATION...Late this evening widespread VFR conditions are
present across the region with scattered high clouds AOA 20-25ft
drifting overhead. The main focus tonight will be a surge of
marine stratus and fog moving northward along the coast which
based on 05-06z satellite observations is just off of Florence.
As this area of fog/low clouds continues to surge northward
overnight into Monday morning, expect IFR/LIFR conditions to
follow, likely starting at KONP around 07-09Z then KAST around
11-14Z (lower confidence in timing for the latter site). Guidance
does hint at some improvement in the early afternoon hours along
the northern portion of the Oregon coast before degrading yet
again by the evening. High confidence in VFR conditions for inland
sites through the TAF period barring a 10-15% chance for isolated
pockets of fog between 12-14z.

KPDX AND APPROACHES...Expect VFR flight conditions to persist with
scattered high clouds AOA 20-25kft. Winds generally remain under
10 knots. -99

&&

.MARINE...The high pressure system, which has been driving the
current conditions across all waters will starts to weaken this
evening. As it weakens, this will result in a southerly wind
shift across all waters as well as a surge of marine stratus
along the coast. This pattern change is expected to be
relatively short lived as the aforementioned the upper level
high becomes displaced by a pair of lows, that are moving south
and east through the fist part of the week. This will bring a
return of northerly winds by Monday afternoon and these
northerly winds are expected to persist through the remainder of
the week. Seas throughout the majority of the week will remain
around 4 to 7 feet with a persistent westerly swell.

Seas are expected to build slightly towards 7 to 9 ft towards the
very end of the week in response to a fresh northwesterly swell
that will impact the waters. This could (30-50% chance) result in
another round of marginal Small Craft Advisory conditions. /42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

www.weather.gov/portland

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