487
FXUS66 KPQR 200506
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1006 PM PDT Thu Sep 19 2024

.UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS... High pressure will maintain dry weather with
temperatures more typical of late September through the start of
next week. A weak front will bring a chance of showers Sunday
into Monday for northern parts of the forecast area, with a
slightly stronger front during the middle of next week. Warm,
dry weather likely to return for the latter part of next week.

&&

.SHORT TERM...Tonight through Saturday night...High pressure
will continue to be the dominant synoptic feature over the
Pacific NW through the weekend. This will maintain variable
onshore flow and result in clouds returning overnight and
scouring out each afternoon/evening. Overall, expect a slight
warming trend though the latter part of this week and into the
weekend as the aforementioned upper level high slowly drifts
inland. This scenario will also result in the development of a
thermally induced trough. Which looks to set up along the
southern Oregon coast and slowly stretch northward through
Saturday. This will also aid in maintaining northwesterly flow,
which will result in breezy west/northwest winds for Friday,
especially over the higher terrain and through the middle and
eastern end of the Columbia Gorge. For the start of the weekend
expect less wind, less clouds and tad warmer conditions. Daytime
highs will generally be around seasonal norms or just a touch
higher. So, expect daytime highs through Saturday to be in the
mid to upper 70s across the inland portions of the forecast area
and temperatures along the coast running about 10 degrees
cooler IE the mid to upper 60s. /42

.LONG TERM...Sunday through Thursday...Sunday looks to feature
a fairly zonal upper level flow regime across the Pacific
Northwest, maintaining dry and seasonable weather with inland
high temperatures in the mid to upper 70s. A weak upper level
disturbance skirting the Canadian border will bring a slight
chance of rain across southwest Washington and far northwest
Oregon Sunday evening into Sunday night, but expect most
locations to ultimately remain dry. Medium range guidance
continues to converge on a warmer and drier solution for the
start of next week, with ensemble clusters and 12z deterministic
models both showing good agreement on an upper level ridge
building over the Pacific Northwest on Monday and shifting
inland on Tuesday. This will bring well above normal
temperatures to the area on Tuesday as highs climb into the mid
to perhaps upper 80s in the interior valleys. The potential for
temperatures higher than that appears rather minimal as latest
probabilistic guidance gives only about a 10 percent chance to
reach 90 degrees in the Portland area and closer to a 30 percent
chance from Salem to Eugene. Any heat concerns look to be
limited to just Tuesday as the ridge shifts east of the region
and temperatures trend back down mid to late week. Guidance also
depicts a short lived period of offshore flow developing late
Monday into early Tuesday. Not overly concerned about east winds
at this time given the progressive nature of the pattern and
fairly modest offshore pressure gradients, but will be something
worth keeping an eye on for those in the fire weather community
as roughly half of European ensemble members depict wind gusts
reaching 25 mph in the vicinity of the Columbia River Gorge late
Monday into early Tuesday. Still some uncertainty beyond
Tuesday as the ridge shifts east to the Rockies, with guidance
remaining split on the strength and timing of an upper level
trough arriving Wednesday into Thursday. NBM mean solution
depicts temperatures moderating to near seasonal norms with
chance to slight chance PoPs returning to coastal and northern
parts of the area during the middle of the week. /CB


&&

.AVIATION...Upper level ridge with fairly dry northwest flow
aloft persists tonight into Friday. Coastal stratus has begun
to build north of Tillamook this evening and we`ll likely see a
similar repeat of stratus redevelopment after 12-13z inland
terminals(40-70%), especially across northern parts of the
forecast area around the Portland Metro area. Any low stratus
dissipates by the afternoon. Generally expect north to northwest
winds, increasing during the afternoon.

PDX APPROACHES...VFR expected with variable high clouds tonight.
There is around a 50-70% chance of MVFR CIGS redevelopment
between ~13-19z Friday followed by a return to VFR. Expect
northwest winds to around 6-8 kt Thursday afternoon. -Schuldt/DH

&&

.MARINE...
Not much change as high pressure persists over the
coastal waters, resulting in a summer like pattern of northerly
winds today through Friday. As the thermal trough strengthens over
the southern Oregon coast, winds will likely gust up to 20-25 kt
over the outer coastal waters this afternoon through tonight. Also
expect winds to gust up to 25 kt across the inner coastal waters
south of Cape Foulweather through this evening. The Small Craft
Advisory continues to cover the increased winds and choppy seas
expected through tonight. Pressure gradients across the coastal
waters weaken somewhat over the weekend, likely resulting in a
decrease in north to northwest wind speeds.

A persistent northwest swell will maintain seas around 6 to 8 ft
through Friday, with a dominant period of around 8 to 10 seconds.
Seas then expected to subside back to around 5 to 6 ft for the
weekend. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ253.
     Small Craft Advisory until 5 AM PDT Friday for PZZ271>273.
&&

$$

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