Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 180957

Area Forecast Discussion
National Weather Service Portland OR
255 AM PDT Thu Apr 18 2024

High pressure over the region will remain through Friday,
maintaining mild sunny days and cool clear nights. Offshore flow
increases a bit for today, and more so for later tonight through Fri,
with breezy easterly winds on the west slopes of the Cascades and to
some degree, the Coast Range. Will return to cooler conditions this
weekend, as a front pushes across the region. Unsettled weather
continues into early next week.

.SHORT TERM...(TODAY THROUGH SATURDAY)...High pressure is building
over the region today, with sunny skies. After a  cool start, will
see temperatures rise back into the 60s today, even along the coast.
Offshore flow will increase today, see thermal trough along the coast
and high pressure sits east of the Cascades. This will allow for
increasing offshore flow. As such, should see east to northeast winds
gusting 20 to 30 mph along the coast later this afternoon into this
evening. Generally, gusts 15 to 30 mph along the coast and higher
terrain of the Coast Range and Willapa Hills. But, the offshore flow
will contribute to downsloping winds, with breezy conditions will be
on the west slopes of the Cascades, with gusts 35 to 50 mph on more
exposed spots, and in parts of the western Columbia Gorge into
eastern parts of the Portland/Vancouver metro. Overall, not enough to
warrant any advisories.

But, these offshore/downsloping winds will boost the temperatures and
lower humidities this afternoon. Likely to see temperatures across
the interior will climb to upper 60s to lower 70s today. Event the
coast will be rather mild, with many areas well into the 60s. Few
spots could reach into the 70s as well.

Winds ease a bit tonight, but will maintain offshore flow. As such,
not as cool as past few nights. Breezy easterly winds in the Cascades
will keep mid-slopes as well as areas along the coast rather mild,
with lows 45 to 50, and lower 50s in few spots.

Models have been persistent in showing the strongest offshore being
on Friday, though only a bit stronger as compared to today. Even so,
will maintain breezy east to northeast winds across the region. Like
Thursday, will be a warm day, with highs into the lower to middle 70s
inland, and 65 to 75 along the coast. Will see wind-reversal along
the coast in the afternoon, with east to northeast winds becoming
southerly to south of Florence in the afternoon, and as far north as
Newport by sunset. This as thermal trough shifts inland over the
Coast Range. This will allow for cooler ocean air to spread back
across the coastal zones at that time. But, offshore flow persists
on to the north overnight, such as at Astoria. Likely be one of
those afternoons where Newport is 59 with light south wind and
Astoria is around 70 with an east wind in the late afternoon.

Changes gradually arrive Fri night into early Sat, as a front well
offshore approaches. Will see offshore flow gradually weaken Fri
night, with increasing clouds later Fri night into Sat am. Timing
still suggest showers or pockets of light rain spreading to the coast
by midday Sat, and pushing inland during the afternoon. Again, not a
strong front, as rainfall expected on Sat being 0.10 to 0.25 inch
along the coast/coastal mtns, and 0.02 to 0.10 for lowlands form
Cowlitz Valley through the Willamette Valley. Will be much cooler on
Saturday, thanks to clouds and onshore flow. Highs only in the 50s
along the coast, and lower to middle 60s inland.   /Rockey

.LONG TERM...SUNDAY THROUGH WEDNESDAY...Onshore flow, with clouds and
few showers around for Sat night into Sun. Ensemble guidance shows
good agreement on a shortwave ridge moving through the area Sunday
afternoon, though uncertainty still exists on how long it`s
expected to continue. Monday looks dry, but another front will bring
cooler unsettled weather again for Tue and Wed.     /Rockey/JLiu

.AVIATION...VFR thresholds prevail through the entire TAF period.
Winds north to northeast a thermal trough develops along the
coast and Willamette Valley through the day. Wind gust 15-20 kt
along the coast as well as inland area this afternoon in to
evening hours. Winds turn more east to northeast overnight into
Friday as high pressure settles east of the Cascades. East winds
35 to 40 kt possible through the Gorge on Friday.

PDX AND APPROACHES...VFR conditions expected through the entire
TAF period. Winds become more easterly and strengthen to around
13-17 kt after 18-19z Thu, with gusts up to 25 kt. Winds settle
after 03-05Z Fri to 10 kt or less. /mh

.MARINE...High pressure off the WA/B.C. coast continues to move
more onshore through the day along with a strengthening thermal
trough along the south Oregon coast. The high pressure will
shift inland later today and tonight, shifting winds front
northerly to easterly. This configuration breaks down Friday night
as a Pacific front approaches and moves through the waters
Saturday. Will maintain Small Craft Advisories through this
evening across the waters with northerly wind gusting to 25 to 30
kt which will bring choppy seas.

General seas through the weekend of 4 to 7 feet at 11 to 17
seconds, consisting of a long period southwest swell or a shorter
period west to northwest swell. -Batz/mh


PZ...Small Craft Advisory from 3 PM this afternoon to 8 PM PDT this
     evening for PZZ251-271.

     Small Craft Advisory from 3 PM this afternoon to 11 PM PDT this
     evening for PZZ252-253.

     Small Craft Advisory until 11 PM PDT this evening for


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