Mehama, Oregon Weather Forecast Discussion

479
FXUS66 KPQR 202230
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
330 PM PDT Sat Sep 20 2025
.SYNOPSIS...A Fall-like front will bring a quick shot of rain
to the region tonight into Sunday before drier and milder
weather return early next week and persist through at least the
middle of next week.
&&
.DISCUSSION...Now Through Friday...The forecast remains
largely unchanged in the short term. Conditions are dry across
the area and are expected to remain dry until late this evening.
Winds have turned southwesterly ahead of an approaching cold
front which can be seen oriented southwest to northeast well
offshore. The front will continue to drop southeast toward the
PacNW with precipitation reaching the south Washington and north
Oregon coasts between 10 pm and 1 am Sunday. Expecting
precipitation to enter the Willamette Valley between 4 and 6 am
on Sunday.
Rainfall totals are expected to the highest along the coast, where
0.50 to 0.75 inches appear likely, with maximum values north of
Tillamook. Inland amounts should range from 0.10 to 0.40 inches,
with highest totals northeast of Aurora and into the eastern parts
of the Portland/Vancouver metro. Clusters indicate a 30 to 60%
chance of wetting rain (CWR) across the area Sunday, rapidly
decreasing by the evening. Instability is limited, but there remains
a 5-10% chance of thunderstorms, mainly near the coast or coastal
mountains during frontal passage.
Sunday will be noticeably cooler with highs in the 60s at the coast
and low 70s inland. Behind the front, conditions dry out quickly
with highs increasing Monday and Tuesday. High pressure across
the northeast Pacific will shift eastward over the West Coast on
Monday. Inland highs will rebound to the upper 70s by Monday,
with about a 40-70% chance of reaching 85 degrees on Tuesday.
Models solutions have trended drier for the middle and end of
next week, keeping the area under the influence of high
pressure. There remains a low chance (10-20%) for dry and windy
conditions to develop across part of the Cascades Tuesday
evening. These dry and windy conditions would consist of RH at
or below 25% and sustained winds of 15 kt or greater.
Probabilities have been pretty consistent in the 10-20% range
so something to continue to watch. ECMWF and GFS ensemble
members have Wednesday and Thursday remaining completely dry
and around 10-15% of members bringing in light precipitation on
Friday. Temperatures remain in the upper 70s to low 80s through
Friday. -Batz/Hall
&&
.AVIATION...High pressure aloft will give way to increasing
onshore flow ahead of an incoming cold front that arrives late
tonight. This will maintain coastal stratus along most of the
coast with predominantly MVFR and IFR conditions persisting into
Sunday. Farther inland, conditions will remain predominantly VFR
through 12z Sunday before conditions deteriorate into MVFR
thresholds between 12-18z Sunday as a band of rain tied to the
front pushes into the Pacific Northwest. It should be noted that
there is a 10-20% chance at any given hour that conditions drop
down into IFR thresholds between 14-18z Sunday. The front will be
moving from northwest to southeast so the window for IFR
conditions will be on the early side of that time window for the
Portland TAF sites and later in that time window for KSLE and
particularly KEUG.
KPDX AND APPROACHES...High pressure over the region will maintain
VFR conditions through 12z Sunday. A cold front and attendant band
of rain will spread over the site Sunday morning. This will bring
a high probability (80-90% chance) of MVFR ceilings spreading over
the site between 12-18z Sunday. Conditions appear likely to
deteriorate rapidly between 12-14z with the arrival of the rain.
As a result, there is a 10-20% chance at any given hour between
14-17z Sunday of conditions dropping into IFR thresholds.
&&
.MARINE...Seas are currently hovering around 5 to 6 ft at 11-12
seconds. A front will drop southeastward across the waters
overnight. This should result in southerly winds increasing across
the waters overnight. Winds appear most likely to peak between 2am
and 6am across the waters with Small Craft Advisory level wind
gusts of 25 kt across the inner waters north of Cape Foulweather
while similar magnitude winds farther offshore (beyond 10 NM) will
primarily be limited to areas north of Cape Falcon. Regardless, the
strongest winds appear most likely to occur within 10 NM of the
mouth of the Columbia River as a weak and short-lived coastal jet
develops. There is an 80% chance that seas climb into the 7-9 ft
range by Sunday morning before temporarily subsiding and then
climbing again as a westerly swell moves into the waters and
pushes seas into the 7-11 ft range by the end of Sunday night.
High pressure then returns to the northeast Pacific. This will
result in northerly winds developing across the waters late
Monday into Tuesday. A weak front approaches the Pacific Northwest
from the northwest midweek, but appears to stall well offshore and
dissipate so few to no impacts are anticipated.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 11 PM this evening to 7 AM PDT Sunday
     for PZZ210.
Small Craft Advisory from 10 PM this evening to 7 AM PDT Sunday
     for PZZ251-252.
Small Craft Advisory from 8 PM this evening to 6 AM PDT Sunday
     for PZZ271.
&&
$$
www.weather.gov/portland
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NWS PQR Office Area Forecast Discussion