711
FXUS66 KPQR 091016 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
316 AM PDT Thu May 9 2024

.SYNOPSIS...A stout ridge of high pressure continues to build
across the region the latter half of the week resulting in a
prolonged period of dry weather and rapidly warming temperatures
day to day. It still appears near record breaking heat is in
store Friday into Saturday`s daytime highs climb in the mid 80s
to near 90 across the inland valleys. Cooler onshore flow
returns Saturday night into Sunday resulting in slightly cooler
temperatures for the early to middle portion of next week albeit
still near to slightly above seasonal norms.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...Ridging continues, with
essentially no cloud cover throughout the CWA as of 3am Thursday.
Going forward through Thursday and Friday the ridge will continue to
amplify, tilting eastward into British Columbia and increasing
offshore flow over the Pacific Northwest. Temperatures warm going
into Thursday, with the warmest temperatures on Friday and Saturday
afternoon. Given the development of low-level offshore flow and
surface thermal trough building overhead as well, confidence is very
high(90-99%) in afternoon temperatures reaching into the low 80s
across the inland valleys Thursday followed by another 6-10 degree
jump into the mid/upper 80s to near 90 Friday. Temperatures across
the Willamette Valley, SW Washington, and other inland valleys
appear very similar on Saturday compared to the day prior
(Friday) - both days present a 40-60% chance to break 90
degrees in the Portland/Vancouver Metro according to the NBM.

The coast will be more uncertain with regards to temperature, as
model guidance is beginning to show the thermal trough shifting
inland Saturday, trending towards cooler temperatures. High
temperatures on Friday look to remain around the low 70s, but
Saturday sees much cooler high temperatures into the mid 60s.
Saturday looks to only have a 10-30% chance of being above 70 at the
coast.

These unseasonably warm temperatures will no doubt cause some
people to flock to the rivers, lakes, and ocean beaches of SW
Washington and NW Oregon. It is important to remember that
rivers and lakes remain dangerously cold with water temperatures
mainly in the 40s. Such temperatures can easily cause cold
water shock for those without proper cold water gear. The bright
sun and warm temperatures can make the cold water look
refreshing, but the consequences of jumping in could be deadly.
Be sure to bring a life vest and be extremely cautious around
area rivers, especially given the swift currents also in place!
-Schuldt/JLiu


.LONG TERM...Sunday through Wednesday...More widespread cooling
is expected on Sunday as the ridge of high pressure withers in
response to a weak upper-level shortwave pressing eastward
towards the coast. The axis of the near surface thermal trough
also shifts east of the Cascades into the Columbia Basin -
widespread westerly onshore flow returns. The marine layer will
likely remain too shallow for much in the way of morning
cloudiness inland through Sunday, but the upper ridge may weaken
enough for some low clouds to push into the inland valleys for
a few hours Monday morning. Cannot rule out patchy light drizzle
at the coast Sunday night into Monday morning as well,
especially given the weak upper- level shortwave progressing
overhead providing some added support.

WPC cluster analysis is beginning to move more towards a solution
favoring ridging re-developing by the middle of next week. Around 80%
of ensemble members display relatively strong ridging by Wednesday
next week, allowing temperatures to climb back into at least the
upper 70s to low 80s. Still around a 20% chance of another trough
developing, which would bring more seasonable temperatures and light
rain showers back to the area. -Schuldt/JLiu


&&

.AVIATION...High pres will remain over the region, with dry
northerly flow aloft. This will maintain VFR, with variable high
clouds at times. Low level northerly flow will kick up by midday,
with winds gusting 25 to 30 kt along the coast, and 15-25 kt
farther inland including the inland TAFs sites. Winds ease
tonight, with VFR continuing.

PDX AND APPROACHES...High pressure will maintain VFR with variable
high clouds. Will see north to northeast winds by midday, with
gusts 15-20 kt for the afternoon into early evening.

&&

.MARINE...No big changes, as strong high pressure remains anchored
offshore. Meanwhile, thermal trough will hug the south Oregon
coast, building northward later today into tonight. With this
pattern, will maintain gusty northerly winds on the waters, with
gusts 20 to 25 kt today north of Cascade Head, and gusts 25 to 30
kt to the south. As thermal trough builds north later today into
tonight, will see winds near shore relax back below 20 kt. Gusty
winds will continue offshore well into overnight hours.

Thermal trough will push the tighter pressure gradient further
offshore later tonight and Fri, as the thermal trough expands
northward along the north Oregon coast. This will push the gusty
north winds farther offshore, with lighter east to northeast winds
on most of the coast waters, especially nearshore. But, with the
thermal trough shifting back to the Coast Range Fri evening, will
see wind flip back to north or northwest Fri evening.

Seas mostly 5 to 8 ft today into tonight, with the higher seas
more choppy as being dominated by the gusty winds. Seas stay at 5
to 6 ft into Sat.

Thermal trough will shift much farther inland on Sat and Sun, with
north to northwest winds returning to the coastal waters. Will not
be as strong, but generally gusts 20 to 25 kt at times in the
afternoons and early evenings. Seas mostly 6 to 8 ft.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 8 AM today for PZZ210.
     Small Craft Advisory until 11 PM today for PZZ251>253-271
     Small Craft Advisory until 5 AM Friday for PZZ272-273.
&&

$$

www.weather.gov/portland

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