727
FXUS66 KPQR 200927
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
226 AM PDT Sun Apr 20 2025

.SYNOPSIS...An upper level trough will bring near normal to slightly
below normal temperatures through Monday along with chances for rain
showers on Sunday. Then, an upper level ridge will bring dry weather
and warmer temperatures Tuesday through Thursday with plentiful
sunshine. Chances for rain showers return to the area Thursday night
into Friday.

&&

.SHORT TERM...Now through Monday night...Weak showery conditions
combined with slightly depressed temperatures continue through the
middle of the upcoming week. Currently between systems as of 2am
Sunday, with a slightly more defined push of moisture expected to
arrive by early Sunday morning. Between 5am Sun and 5 am Mon, around
0.05-0.15 inches of rain accumulation expected for areas north of
Salem, as the primary low moves further to the north. Closer to
0.2-0.3 inches in the Cascades during this time due to terrain
enhancement. With this system, some very isolated thunderstorms may
be possible, but with a strong dry layer above 700 mb, any convection
will be extremely shallow. NBM thunder probabilities under 15%
throughout the region on Sunday afternoon, with CAPE values around
50-75 J/kg. Most likely will only see a few isolated cells with a
flash or two of lightning, and possibly brief minor pea-sized hail.

Overnight low temperatures don`t change much through Wednesday night,
though Monday night likely sees the coolest temperatures during this
period due to clearing cloud cover. The southern Willamette Valley
reaches into the mid to upper 30s late Monday night/Tuesday morning.
Low possibility of frost at that time. An exception will be the upper
Hood River Valley, which could see lower temperatures approaching
freezing. Possibility of freeze/frost headlines Monday night there.
/JLiu

.LONG TERM...Tuesday through Saturday...The long term forecast is
highlighted by warmer and drier weather with plenty of sunshine,
aside from Friday when conditions turn cooler and cloudier with
increasing chances for rain showers due to a slightly more impactful
low moving through. Prior to the potential frontal system on Friday,
models and their ensembles are in good agreement each day will be
warmer than the previous day from Tuesday through Thursday. This is
in response to an upper level ridge that will be moving over the
Pacific Northwest at that time. Model spread for high temperatures is
low, generally 10 degrees or less, suggesting confidence is high in
the temperature forecast. Expect widespread highs well into the 60s
to lower 70s on both Wednesday and Thursday, except upper 50s to
lower 60s at the coast. Cannot rule out highs upwards of 75 to 80
degrees for the Willamette Valley and Portland/Vancouver metro (5-15%
chance Wednesday and a 10-30% chance Thursday).

After a few warm and dry days, cloud cover will begin to increase
Thursday night into Friday in response to an incoming Pacific frontal
system. Although there are a few ensemble members from the GEPS/ENS
that are dry on Friday, the vast majority are not. No members are dry
in the GEFS ensemble. The main differences lie with the exact timing
of precip and when it will move into the area. The probability for
0.25 inches of rain or more falling between 5am Friday and 5am
Saturday ranges between 25-50%, with the highest probabilities in the
Cascades. -TK

&&

.AVIATION...Northwest to westerly flow aloft continues through the
TAF period. A weak front is slowly pushing inland into Sunday
morning, with increasing clouds and chances for rain showers,
mainly north of KSLE. There`s a 60-90% chance of MVFR CIGs along
the coast through the TAF period, though expecting the CIGs to
bounce between MVFR and VFR. Inland locations are more likely to
see a mix of VFR and MVFR conditions after 09-12Z Sunday, with
about a 30-60% chance of MVFR CIGs, highest near KPDX and KTTD.
Inland conditions expected to return to VFR after 18-21Z Sunday.
Winds remain generally less than 10 kts, north to westerly along
the coast and mainly variable inland, becoming northwesterly after
21z Sunday.

PDX AND APPROACHES...Expecting low end VFR to high end MVFR CIGs
around 2500-4000 ft through around 18-21z Sunday along with a
chance of rain showers after 12z Sunday. Light southwest winds,
shifting northwest after 18-21z Sunday. -DH/HEC

&&

.MARINE...Strong high pressure offshore will maintain northerly
winds across the coastal waters. A weak front moves across the
waters on today as winds become more northwest, but gusts remain
less than 20 kts. By Monday, the thermal trough strengthens over
the southern Oregon coast, increasing the northerly pressure
gradients again for early next week. Northerly winds off the
central Oregon coast likely increase with gusts up to 20-25 kts by
Monday evening, continuing through at least midweek. Seas are
expected to persist around 6 to 8 ft at 10 seconds through the
middle of the week. -DH/HEC

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

www.weather.gov/portland

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