468
FXUS66 KPQR 241059
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
359 AM PDT Fri May 24 2024

.SYNOPSIS...Low pressure brings cool and showery weather
through Saturday. Warmer and drier conditions return on Sunday,
with temperatures peaking on Monday as high pressure builds
east of the Cascades. More unsettled weather may return towards
the middle of next week.

&&

.SHORT TERM...Now through Sunday Night...Radar shows light rain
spreading over the north Oregon and south Washington coastal
areas early this morning as the latest in a series of shortwave
troughs arrives over the region from the northwest, with a weak
surface front located over the coastal waters as of 3 AM Friday.
Light rain will continue to spread inland through later this
morning as the front moves onshore and dissipates. Expect no
more than a tenth of an inch of rain for most locations today,
with slightly higher amounts possible for northern coastal
areas. Abundant cloud cover will hold high temperatures down in
the low 60s this afternoon for most locations. Cool and showery
weather persists tonight into Saturday as trailing shortwave
energy tracks across southern BC and Washington. Additional rain
amounts will be minimal for most locations tonight through
Saturday, with northwest flow helping to focus the highest QPF
amounts along orographically favored terrain in the north
Oregon Cascades and the Coast Range. All told, expect rainfall
totals generally around a quarter inch in these locations
through the weekend with a few locations closer to a half inch.
Snow levels still look to fall to 3500-4000 feet late tonight
into early Saturday, bringing a dusting of snow as low as the
Cascade passes through Saturday morning.

Rain begins to taper off by Saturday evening as the trough
departs east of the Cascades and makes way for the next brief
period of shortwave ridging Saturday night. Sunday will then be
characterized by benign onshore flow with temperatures
rebounding into the upper 60s to near 70 in a few locations.
Can`t rule out a few showers along the far northern coastal
areas, but most of the area should remain dry to cap off the
weekend. /CB

.LONG TERM...Monday through Thursday...Next week begins with
warmer temperatures as WPC ensemble clusters continue to show
good agreement on an amplifying ridge east of the Cascades,
resulting in dry weather and temperatures well into the 70s
across most of the area on Monday. A few spots closer to the
Portland metro still have an outside chance to hit 80 degrees,
with NBM probabilities holding around 30 percent. The forecast
beyond Monday has shifted a bit over the past 24 hours as
guidance depicts the ridge axis shifting farther east over the
Rockies on Tuesday. The net effect of this shift is to place the
Pacific Northwest closer to the influence of an upstream trough
over the NE Pacific, lowering temperatures and introducing a
chance of rain to the coastal areas as early as Monday night.
The bulk of the guidance continues to favor the return of a
troughier pattern towards the middle of next week. Despite some
differences in timing and location of specific features, there
is greater confidence in increasing rain chances as most
individual ensemble members depict at least some precipitation
across the area Wednesday into Thursday, with temperatures
settling closer to seasonal norms around 70 degrees. /CB

&&

.AVIATION...VFR conditions continue to prevail early this morning
as our next weather disturbance begins to move into the Pacific
Northwest. Rainfall from a weakening front progresses into the
coast 14-18z today then over the interior valley 18-22z. HREF
indicating 40-60% chance for MVFR cigs below 3000 ft at the coast,
increasing to 60-80% chance by 18Z. There is also a 60-70% chance
for IFR at the coast 20-23Z Fri. Inland there is a 20-40% chance
for cigs 12-17Z Fri over the valley, but better chances(40-80%)
22-02Z Sat. This may be overdone a bit but much the latest
deterministic guidance has begun coming into better agreement on
a period of MVFR cigs (2.5-3kft) for inland sites during this same
timeframe.

PDX AND APPROACHES...VFR conditions expected through this morning
but it`s at least worth mentioning there`s a 20-30% chance for
cigs near 3000 ft 12-17Z Fri. Much better chances for 2.5-3kft
CIGS between 21z Fri and 00z Sat followed by a return to VFR.
Winds remain fairly light, generally less than 10 knots.
-Schuldt

&&

.MARINE...A slightly more active pattern is expected Friday into
Saturday as the next system drops south-southeastward into the
Pacific northwest. Along with precipitation, expect northwest winds
to ramp up through the day with gusts up to 20-30 kt and seas
also building towards 8 to 10 ft with a dominant period of 8 to
10 seconds. With this in mind, periods of steep and choppy seas
along with gusts above 21-22 knots (primarily outer waters)
have lead to the issuance of a Small Craft Advisory for the
outer/inner waters and the Columbia River Bar. It`s worth noting
the latter location will also experience a strong ebb current
Saturday morning as well helping to steepen seas locally.
Another weak ridge of high pressure brings the return of benign
conditions by Saturday night into Sunday. Looking ahead, an
upper-level low pressure parked over the Gulf of Alaska keeps us
on the periphery of additional weak disturbances passing mainly
to our north Sunday night through Monday night before it drops
southward around the middle of next week again increasing
winds/seas. -Schuldt

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 11 AM PDT
     Saturday for PZZ210-251>253-273.
     Small Craft Advisory from 2 PM this afternoon to 11 AM PDT
     Saturday for PZZ271-272.
&&

$$

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