687
FXUS66 KPQR 190317 AAA
AFDPQR

Area Forecast Discussion UPDATED
National Weather Service Portland OR
815 PM PDT Tue Jun 18 2024

...EVENING UPDATE, for aviation weather.

.SYNOPSIS...Much drier and warmer through the remainder of the
week with building high pressure. High probability of temperatures
into the 90s inland. Even with the rather warm temperatures, water
in areas rivers and lakes will remain on the chilly side. Cooler and
wetter pattern approaching on Sunday, with increasing chances for
precipitation later next week.

&&

.SHORT TERM...Now through Friday...High pressure over the region
will maintain clear skies overnight. Breezy evening north winds will
ease after sunset. May have some patchy low clouds along the coast
from Astoria northward, as well as inland through the Cowlitz Valley
late tonight into very early Wed.

The upper level rex block is slowly developing overnight into
Wednesday which will enhance the high pressure at the surface.
While there is a ridge forming at the low levels, ensembles are
still forming a midlevel trough at 500 mb. Closer to the
surface, a strengthening thermal trough extending from the
California Central Valley into south-central Oregon will induce
cross barrier flow over the Casacdes and subsequent downsloping
for the interior lowlands. This will send highs well into the
80s on Wednesday afternoon for areas away from the coast, with
NBM probabilistic guidance indicating around a 35% chance to
reach 90 degrees across the Portland metro area, and 15% in the
central Willamette Valley. Temperatures will rise further on
Thursday and Friday with much higher confidence for highs in the
90s. One shift from previous forecasts is the extent of these
high temperatures. While they formerly covered mainly the
greater Portland-Vancouver Metro and the western Columbia River
Gorge, they have spread further south into the Willamette
Valley, and the valleys of the Cascade Foothills. Heat risk
is moderate for the urban areas north of Salem.

.LONG TERM...Saturday through Tuesday...The Rex block slowly
degrades on Saturday as a weak long-wave trough dips southward.
Still will be warm and dry, but with incoming onshore flow,
conditions will slowly improve. More substantial cooling should
come on Sunday as WPC ensemble clusters show good agreement on
the next upper level trough beginning to impact the Pacific
Northwest, with temps back closer to seasonal norms in the low
to mid 70s. Precipitation continues to see low probabilities as
the core of the upper trough remains north over BC. Northwest Oregon
and southwestern Washington will see the highest chances for
rainfall, but again are minimal.      -Muessle/CB


&&

.AVIATION...High pressure will maintain VFR under clear skies
tonight into Wed. Still have north winds gusting 20 to 25 kt along
the coast this evening, but those winds will ease by midnight. Could
see patchy IFR clouds along the coast from Seaside northward along
the Washington coast later tonight into early Wed am, as well as in
the Cowlitz River Valley as well.

PDX AND APPROACHES...VFR under high pressure tonight and Wed. Can
not rule out some patchy IFR stratus (CIGS 500 to 900 ft) over Clark
county between 11Z and 15Z Wed, mainly north and east of Vancouver
near the foothills. But, am not expecting that to affect PDX, so
will keep 06Z TAF for PDX free of clouds.            /Rockey

&&

.MARINE...Not much change as high pressure offshore is expected
to persist through the week. Northerly winds around 15-20 kt will
continue into this evening. A Small Craft Advisory will be in
effect south of Cape Falcon through tonight. Expect will see
periods of winds gusting up to 25 kt through Friday during the
late afternoon and evenings. The northern zones are added tomorrow
afternoon as winds increase across all waters. Small Craft
Advisory is up through 11 PM Wednesday but will likely need to be
extended later into the week. Seas around 4 to 6 feet will
generally be wind driven through the week. A weak front is
expected to approach the waters this weekend. -Batz/DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM to 11 PM PDT Wednesday for
     PZZ251-271.
     Small Craft Advisory until 11 PM PDT Wednesday for PZZ252-272.
     Small Craft Advisory until 11 PM PDT Wednesday for PZZ253-273.
&&

$$

www.weather.gov/portland

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