Lake Oswego, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

893
FXUS66 KPQR 041610 AAB
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
910 AM PDT Mon May 4 2026

Updated aviation discussion.

&&

.SYNOPSIS...Cooler but still above-normal temperatures with
largely dry weather expected through much of the workweek
beneath broad and persistent upper-level ridging. Chances for
rain increase Friday into Saturday as the ridge deamplifies, but
uncertainty in timing and coverage of precipitation continues.

&&

.DISCUSSION...Now through Sunday...Broad upper-level ridging
spanning the Northeastern Pacific and western CONUS is favored
to remain in place with a slight eastward tendency through the
next week. An upper cutoff low over California which supported
offshore flow resulting in record high temperatures on Sunday
will exit eastward more quickly, favoring a return to more
seasonable northerly to northwesterly flow aloft. Despite upper
heights rising in the wake of the departing low, temperatures
will actually trend cooler while also remaining seasonably warm
thanks to this pattern change. Through midweek, renewed onshore
and southerly flow will maintain fairly steady daytime high
temperatures in the 60s along the coast and in high terrain and
in the 70s to near 80 degrees within inland valleys, some 10 or
so degrees above normal. This southerly surge will see marine
overcast and periods of mist and drizzle along the coast and
clouds reaching inland through coastal gaps each night, before
retreating back toward the coast during the day. As such,
largely dry and tranquil weather is expected for most.

By the end of the workweek, long-range ensembles depict a
shortwave trough transiting the apex of the ridge, bringing
cooler temperatures closer to seasonal norms as well as the most
widespread chances for rainfall to the region. There is still
uncertainty in the timing and distribution of precipitation, but
the ensemble consensus favors rain occurring some time between
Friday morning and Saturday afternoon, with the highest chances
to the north and in areas of higher terrain and lower chances
to the south and for valley locales. At this time, potential
rainfall amounts look to be light, generally 0.1 inch or less.

Beyond this late-week system, ridging aloft will most likely
rebuild, favoring a return to dry and warmer-than-normal
conditions. There remains uncertainty, however, in the
position, orientation, and amplitude of ridging, which could
affect the sensible weather on the ground. -36

&&

.AVIATION...A strong southerly marine surge has resulted in
widespread low stratus this morning, which is impacting all
terminals as of 16Z Monday. Satellite and surface weather
observations showed low stratus expanding across the entire
Willamette Valley and most of the Portland metro, while the coast
remains socked in. Ceilings ranged between 1000-2000 ft with this
stratus deck, except down to 500 ft at KONP. Expect this stratus
deck to scatter out sometime between 18-21Z Monday for inland
terminals, clearing KPDX, KTTD, KHIO, KUAO and KSLE first and KEUG
last. With a similar pattern in place tonight, expect another
southerly marine surge to occur, bringing a return of low stratus
to KEUG (60% chance for MVFR ceilings beginning around 09Z
Tuesday, increasing to a 90% chance by 12Z Tuesday). This stratus
deck may also spread northward into KSLE between 12-15Z Tuesday
(30-50% chance). Confidence is lower for KUAO, KTTD, KPDX, and
KHIO, as probabilities only peak around 15-30% for these sites. If
these TAF sites do observe another round of low stratus Tuesday
morning, it would likely hold off until 15-16Z Tuesday, similar to
today.

Meanwhile, the coast will most likely remain socked in
through today and tonight. One exception is at KAST, where low
clouds may briefly scatter out and give way to VFR flight
conditions sometime between 20-23Z Monday (60-70% chance).
However, there is a 60-70% chance IFR to low-end MVFR ceilings
will fill right back in by 01Z Tuesday.

Southerly to southwesterly winds will continue at all terminals
through this afternoon, sustained between 5-10 kt with occasional
gusts up to around 15 kt. A sea breeze front will push inland
between 00-03Z Tuesday, bringing an abrupt shift to westerly
winds, except northwesterly in the Portland metro.

KPDX AND APPROACHES...A broken low stratus deck has expanded over
the KPDX terminal as of 16Z Monday with ceilings around 1700 ft.
Expect this low stratus deck to persist through approximately
18-19Z Monday before scattering out thereafter. Southerly winds
will persist around 10 kt through this afternoon before shifting
to the west to northwest after 00Z Tuesday with an incoming sea
breeze front. There is a 15-30% chance for another round of low
stratus with MVFR ceilings between 10-18Z Tuesday. -23

&&

.MARINE...A southerly surge is underway this morning, bringing
gusty south winds up to 20 kt, marine overcast, and patchy mist
and drizzle to the coastal waters, especially within 20-30 NM
of shore. A diurnal tendency will persist through Wednesday,
with increasing clouds, wind, and chances for drizzle or light
rain at night before clouds recede and winds ease during the
day. A lessening northwest swell will see seas fall from 6-8 ft
today to 4-5 ft by Wednesday.

Winds look to turn northerly Wednesday through Thursday night
with persistent seas of 5-7 ft. A system moving onshore Friday
into Saturday will favor a return of southerly flow and
increased chances for rain showers, before high pressure
rebuilds later this weekend and northerly flow strengthens.
Chances increase late Saturday into Sunday for northerly gusts
of 20 kt, conditions which may be hazardous to small craft. -36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

www.weather.gov/portland

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