West Linn, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

137
FXUS66 KPQR 300944
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
244 AM PDT Wed Apr 30 2025

.SYNOPSIS...Warm and mostly dry conditions expected through Friday
afternoon, with temperatures on Thursday peaking around 10-15
degrees above normal, with some locations, including the Portland
Metro, potentially reaching into the mid-80s. A spring-time front
will bring increasing chances for rain showers later Friday through
Friday night, with temperatures cooling back into the 60s on
Saturday. Expect temperatures to rise again into early next week as
high pressure likely returns to the region.

&&

.SHORT TERM...Today through Friday...A few clouds linger through
this morning, mainly along the coast and Cascades, as an upper
shortwave trough slides east toward the northern Rockies. A more
amplified upper level ridge will begin to slide over the Pacific
Northwest, with clearing skies and dry weather expected through at
least Thursday. Temperatures remain fairly mild today as northwest
onshore flow persists. But, come the first day of May, temperatures
are expected to spike as the ridge amplifies over the region,
pushing 850 mb temps into the 13-15 C range. Weak offshore flow will
also set up early Thursday as a surface thermal trough builds across
the coast range. Marine winds push back onshore later in the day,
except near the Portland Metro which will likely maintain easterly
winds and see temperatures warm into the lower to mid 80s. Marine
influences still look to keep coastal locations more mild by
comparison, with temperatures topping out in the 60s to near 70.

The upper ridge will continue to shift eastward, and by early
Friday, expect a southerly wind reversal ahead of the next weather
system. An upper level trough offshore approaches the region later
Friday with increasing moisture and low level westerly flow. Expect
increasing clouds through the day, with increasing chances for light
rain at the coast. Best chance for showers will likely be along the
Cascades, increasing Friday afternoon through Friday evening. If
skies remain fairly clear allowing surface warming to occur along
the western slopes, pattern recognition suggests there is potential
for thunderstorms near the crest, but chances remain slight, around
15% or less. Overall, the weather will likely remain fairly pleasant
through much of the day, with increasing showers through the
evening. Rainfall amounts through Friday night currently forecast to
be around a tenth of an inch or less, except in the Cascades and
foothills where there is around a 50% chance for wetting rains
exceeding 0.25-0.50 inch. /DH

.LONG TERM...Saturday through Tuesday...Somewhat cooler temperatures
expected on Saturday as the upper level trough slides onto the west
coast. Aside from showers along the Cascades and foothills,
decreasing through the afternoon, much of the area should remain dry
as the upper trough elongates and likely splits. By Sunday, WPC
cluster analysis is in good agreement that the base of the tough
develops into an upper low over southern California, while more
upper ridging begins to nudge back over the Pacific NW into early
next week. This will likely bring another warming trend to the area,
pushing temperatures back into the 70s by Monday. Potential for more
80 degree days increases to around 20-30% through the middle of next
week, while the probability of precipitation remains generally less
than 20%. /DH

&&

.AVIATION...At 0930z Wednesday, surface weather observations
depicted light and variable winds around 5 kt or less across
northwest OR and southwest WA. Expect these conditions to continue
through 12z Thursday.

In addition to the light winds, a cloud deck was evident along
the coast from KAST to KONP with cigs around 3000 ft. Expect this
cloud deck to lift to VFR while scattering out by 16z Wednesday.
Clear skies remain in place for inland areas this morning, aside
from broken low clouds in the Cascades. These low clouds may
briefly backbuild into KTTD and/or KUAO towards 12z Wednesday with
cigs around 3000 ft or less, however the probability of this
occurring is only at 10-30%. Even if this does occur, cloud cover
would likely only last a few hours with clearing after 15-16z.
Given the most likely outcome is for the continuation of clear
skies at both terminals, have decided to maintain VFR flight
conditions in the 12z TAFs. Will maintain VFR conditions for KHIO,
KSLE, KPDX and KEUG as well, as these terminal have even lower
probabilities for low clouds to develop.

PDX AND APPROACHES...VFR conditions and mostly clear skies will
continue through 12z Thursday with light northwest winds around 5
kt. 10% chance for a brief period of MVFR cigs around 3000 ft from
12-15z Wednesday. Have decided not to include this in the 12z TAF
as the most likely outcome is the continuation of clear skies. -TK

&&

.MARINE...High pressure will remain in place through Friday,
resulting in benign conditions with seas under 10 ft and winds
generally under 20 kt. That said, northerly winds should briefly
gust up to 20-25 kt late Wednesday afternoon and evening over the
southern waters. Therefore, a marginal Small Craft Advisory has
been issued for PZZ273 and PZZ253 during that time.

A Small Craft Advisory is also in effect for the Columbia River
Bar from 4-10 AM PDT Wednesday. This is when a very strong ebb
current will result in steep ebb chop with seas up to 8 ft at 8 to
10 seconds, results in rough bar conditions for small craft. -TK

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 10 AM PDT this morning for PZZ210.

     Small Craft Advisory from 4 PM this afternoon to 10 PM PDT this
     evening for PZZ253-273.
&&

$$

www.weather.gov/portland

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