439
FXUS66 KPQR 061015
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
315 AM PDT Sun Apr 6 2025

.SYNOPSIS...A frontal boundary crossing the region will herald
a return to a cooler and wetter pattern with persistent chances
for rain showers through Tuesday night. After a brief break
midweek, additional progressive systems will see additional
chances for precipitation into the weekend. There is a low
probability of hazardous weather.

&&

.DISCUSSION...Now through Saturday...Heights aloft continue to
fall over the region as upper-level troughing digs over the
Northeast Pacific. A surface frontal boundary has begun to move
onshore, bringing scattered to numerous rain showers to coastal
communities and across the Coast Range & Willapa Hills early
this morning. Showers will continue to spread inland to the
Willamette and Cowlitz Valleys through the morning, and
ultimately into the Cascades by this afternoon. The boundary
will progress to the east fairly slowly as its parent shortwave
tracks northward toward western WA and southwestern BC,
yielding rainfall totals through early Monday morning of
0.5-1.0 inches along the I-5 corridor, and slightly higher
amounts of 0.75-1.5 inches in favored regions for upslope
enhancement on the western flank of local terrain.

In its wake, a second shortwave approaching on Monday will see
another round of more widespread shower activity, producing an
additional 0.25-0.75 inches of rainfall along I-5 through early
Tuesday morning, and 0.5-1.5 inches in areas of higher terrain.
As the mid-level cold pool moves overhead Monday and Tuesday,
sufficient instability may allow a few thunderstorms to develop
within more widespread showers. Given low freezing levels as
850-hPa temperatures fall below 0C, any brief thundershower may
produce small hail, most likely during the afternoon each day. A
final reinforcing shortwave will arrive Tuesday, before heights
aloft begin to rise as upper ridging builds over the West.
Temperatures through this period will begin slightly above
normal today, with afternoon highs in the 50s to low 60s, and
trend slightly below normal by Tuesday, when highs will only
reach into the 40s to mid 50s.

Developing ridging will bring a brief warming and drying trend
midweek, with little in the way of precipitation expected
Wednesday through early Thursday and as temperatures rise back
above normal by Thursday. By the end of the week, ensemble
guidance favors a return to the progressive pattern with
increased precipitation chances as the upper ridge over the
Interior West breaks down. The details are low confidence at
this lead time, however there is good agreement that widespread
light rainfall will be favored Friday into the weekend. -Picard

&&

.AVIATION...Radar, satellite, and surface observations as of
1045z Sun show a frontal system moving into northwest Oregon,
bringing rain and a mix of MVFR/VFR CIGs and VIS along the
coast. Conditions remain predominately VFR inland 12-18z Sun,
however, expect CIGs to gradually fall across the region today
as this front pushes eastward. After 18-21z Sun, do have
moderate to high confidence (50-70% chance) for CIGs falling to
MVFR. Meanwhile, there is high confidence (greater than 80%
chance) that CIGs along the coast fall to LIFR/IFR. These trends
in CIGs will hold through the remainder of the TAF period as
the system impacts the area. VIS reductions to IFR/MVFR
thresholds are possible at any given terminal today, especially
during periods of heavier rain. Expect southerly to
southwesterly winds around 5-10 kt or less across all terminals,
with gusts up to 20 kt possible along the coast.

Note: The KAST anemometer remains inoperative. Therefore, KAST
TAF amendments are limited to CIG and VIS.

PDX AND APPROACHES...Predominately VFR thresholds until 19-21z
Sun, when the front moves through and lowers CIGs to MVFR
(50-70% chance). Periods of moderate rain this afternoon may
result in brief reductions in VIS to MVFR (3-5 SM). Winds will
start easterly this morning around 5-10 kt, then shift more
southerly around 18-21z Sun as the front moves through. -Alviz

&&

.MARINE...A frontal system will push through the waters today,
strengthening southerly winds to 10-20 kt with gusts up to 25 kt
today. Confidence in widespread gusts exceeding 25 kt remains
around 60%, but is isolated to the border of the inner and outer
waters (around 10 NM out). A westerly swell will also enter the
waters, building seas to 10 to 12 ft at 16 seconds by Sunday
afternoon. A Small Craft Advisory remains in effect for all
marine zines including the Columbia River Bar from 5 AM Sunday
to 5 PM Monday.

Additional systems will push through the waters early next week,
maintaining breezy southerly winds and elevated seas. The most
notable is a low pressure system forecast to approach the waters
Monday night into Tuesday, with southerly winds forecast to
gust up to 30 kt. Models are beginning to agree on a 1009-1011
mb low tracking through the waters on Tuesday. A low of this
magnitude would likely result in widespread, high-end small
craft wind gusts with occasional gale-force wind gusts. However,
there is a 15-25% chance that this low could strengthen further
and result in more long-lasting, widespread Gales. -Alviz

&&

.BEACH HAZARDS...A westerly swell around 9-11 ft at 15-17
seconds will bring an increased threat of sneaker waves Sunday
to Monday. Therefore, a Beach Hazards Statement for sneaker
waves remains in effect from 5 AM Sunday to 8 PM Monday. Beach
goers should remain aware of their surroundings. Waves can run
up significantly farther on a beach than normal, including over
rocks and jetties. Sneaker waves can suddenly knock people off
of their feet and quickly pull them into the frigid ocean which
may lead to serious injury or drowning. -Alviz

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 5 PM PDT Monday for PZZ210.
     Small Craft Advisory until 5 PM PDT Monday for PZZ251>253-
     271>273.

&&

$$

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