081
FXUS66 KPQR 092201
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
301 PM PDT Thu May 9 2024

.SYNOPSIS...A large eastward tilted ridge of high pressure will
remain overhead through early this weekend, bringing dry weather
and rapidly warming temperatures. Inland valley temperatures
are expected to reach the mid to upper 80s Friday and Saturday -
could see some record breaking highs in urban areas. Saturday
night into Sunday, winds will shift from offshore to onshore
flow, bringing cool yet still above seasonal norm temperatures
into early next week.

&&

.SHORT TERM...Now through Saturday...Ridge continues to build
and tilt eastward into our region, maintaining clear skies.
Today and tomorrow, as the ridge further tilts and moves inland,
offshore flow will increase over the PNW. Temperatures begin to
warm today (up to low 80s inland), with a rapid increase into
tomorrow as offshore flow and ridge strengthening continues. As
a result, Friday and Saturday are expected to be the warmest
days this week. With these aforementioned favorable conditions,
there is high confidence (90-95%) that inland valley
temperatures will exceed 85 degrees F on Friday and Saturday.
There is a 50-60% chance for temperatures to exceed 90 degrees F
on Friday and Saturday, however it looks to be mostly focused
on the Portland/Vancouver Metro and areas surrounding. Other
inland urban areas, such as Salem/Corvallis/Eugene, have a
10-20% chance to exceed 90 degrees F on Friday and Saturday.

There is more uncertainty for temperatures at the coast, as some
model guidance is suggesting that the ridge will shift inland
Saturday, leading to onshore flow moderating and cooling
temperatures. As a result, expect upper 70s to low 80s Friday
with a 50-70% chance to exceed 80 degrees F, decreasing to upper
60s to low 70s on Saturday.

With such unseasonably warm temperatures for early Spring and
coming out of cold weather, there is no doubt people will visit
rivers, lakes, and the ocean for SW Washington and NW Oregon
this weekend. 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, resulting in an involuntary
gasp of air that can lead to drowning. Be sure to bring a life
vest and be extremely cautious around rivers, especially with
snowmelt causing cold and swift currents!
-JH

.LONG TERM...Sunday through Wednesday...Widespread cooling is
expected Sunday as the upper-level shortwave trough moves
towards the coast, weakening the inverted thermal trough
overhead and pushing it eastward. As this trough gets pushed
eastward over the Cascades, widespread westerly onshore flow
will return, bringing more widespread cooling (cooling to low
70s by Monday). 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 north coast Monday
morning as well, especially given the weak upper-level shortwave
progressing overhead providing some added support just north of
our CWA.

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 the low to mid 70s. Still around a 20% chance of
another trough developing, which would bring more seasonable
temperatures and light rain showers back to the area.
-JH/Schuldt

&&

.AVIATION...High pressure will remain over the region, with dry
northerly flow aloft. This will maintain VFR under mostly clear
skies. North winds gusting 15 to 25 kt, except east winds out of
the Columbia River Gorge gusting up to 30 kt through this evening.
Winds ease tonight, with VFR continuing.

PDX AND APPROACHES...High pressure will maintain VFR with mostly
clear skies. East to northeast winds 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 farther
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 from 5 AM to 9 AM PDT Friday for PZZ210.

     Small Craft Advisory until 11 PM PDT this evening for PZZ251>253-
     271.

     Small Craft Advisory until 5 AM PDT Friday for PZZ272-273.
&&

$$

www.weather.gov/portland

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