954
FXUS66 KPQR 182218
AFDPQR

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

.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 high
temperatures, water remains cold. Cooler and wetter pattern
approaching on Sunday, with increasing chances for precipitation
late next week.

&&

.SHORT TERM...Now through Friday...Satellite shows some spotty
cumulus forming offshore and along the Cascades today due to
northwesterly flow. Winds remain elevated along the coast, and
the southern Willamette Valley in areas most susceptible to
these north-northwesterly winds. Will see those winds ease
overnight and become weakly offshore. With the clear skies,
there is a slight chance for some lower patchy stratus and fog
formation along the coast and the Coast Range valleys; the
extent will be minimal.

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...Upper level troughing is expected to remain in place
across the PNW which will maintain flow from the NW. Elongated surface
high pressure stretches from the Gulf of Alaska to off the Oregon
coast. The surface high is expected to slip southward tonight
through Wednesday and will help maintain northerly surface winds
between 5-10 kts on Wednesday. Winds along the coast could be a
touch stronger around 12 kts along with gusts up to 20 kts
tomorrow afternoon. CIGs should remain VFR into early tonight with
scattered fair weather cumulus around 4 kft dissipating late this
evening. HREF guidance suggests marine stratus developing (peak
40-50% chance) along the coast between 8-12Z and being maintained
into Wednesday afternoon. HREF also suggests a bit of stratus
developing along the Cascade Foothills around 10Z and dissipating
by 17Z. There is a 30-40% chance that this impacts the terminals
within the Willamette valley.

PDX AND APPROACHES...VFR conditions should prevail through the TAF
period with scattered cumulus around 4 kft into the evening. Winds
will be from the NW around 5-10 kts, becoming light and variable
overnight. There is a 30% MVFR CIGs develop around KTTD between
10-16Z and a 10% chance clouds make it to PDX. -Batz

&&

.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.
&&

$$

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