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926
FXUS66 KPQR 191826
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1126 AM PDT Wed Jun 19 2024

Updated Aviation Discussion

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.SYNOPSIS...
Much warmer through the remainder of the week under
building high pressure, with moderate heat risk expected from
Portland to Salem Thursday through Saturday. More seasonable
temperatures return Sunday into early next week.

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.DISCUSSION...Clear skies prevail across most of northwest
Oregon and southwest Washington early this morning as low level
northerly flow continues to advect drier air into the region.
Today will mark the beginning of a stretch of well above normal
temperatures lasting through the end of the week as a Rex Block
begins to take shape in the upper levels and a surface thermal
trough continues to strengthen from the California Central
Valley into south-central Oregon. This will induce cross
barrier flow over the Cascades and subsequent downsloping for
the interior lowlands, sending highs well into the 80s this
afternoon for areas away from the coast.

Heat still looks to peak Thursday into Friday as 500 mb heights
continue to gradually rise and 850 mb temps increase to around
15-16 C. Operational NBM and ensemble guidance continue to
depict temperatures ending up right around around 90 degrees
both Thursday and Friday afternoon from the Portland metro down
to Salem, with highs closer to the mid to upper 80s in the south
Willamette Valley and the I-5 corridor in southwest Washington.
One notable change from previous forecast cycles is that NBM
probabilistic guidance has started to back off of some of the
higher end scenarios, with the chance to reach 95 degrees on
Friday down to 25-30 percent in the Portland and Salem areas
compared to around 40 percent 24 hours ago, with chances back
down to around 5 percent in the Eugene area. This lends
increasing confidence in the temperature forecast for the end
of the week as highs around 90 support a moderate HeatRisk for
the Portland and Eugene areas, with overnight low dropping into
the upper 50s helping to mitigate more widespread or cumulative
HeatRisk concerns.

Moving into the weekend, it appears temperatures will remain a
bit warmer on Saturday as recent model runs have signaled a
delay in the expected stronger push of onshore flow as high
pressure shifts east of the region. This is reflected by NBM
probs hanging onto a 50 percent chance to reach 90 degrees on
Saturday for the Portland and Salem areas. More pronounced
cooling will still arrive by Sunday as WPC ensemble clusters
continue to depict the next trough approaching the Pacific
Northwest, dropping temperatures back near seasonal normals in
the low to mid 70s. These more seasonable temperatures will
persist through the early part of next week as the region
remains under the influence of the trough. Models have started
to trend drier with the forecast as the core of the upper low
remains well to the north over British Columbia, with any
low end precipitation chances towards the end of the period now
generally confined to the far north Oregon Coast and southwest
Washington. /CB

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.AVIATION...
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Broad upper level troughing persists over the region
with northwest flow aloft. High pressure will maintain VFR under
mostly clear skies. Onshore flow will increase into the afternoon,
possibly a few gusts up to 20 kts along the coast.


PDX AND APPROACHES...VFR under clear skies. N/NW winds at 5-10 kts
expected.
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.MARINE...
Not much change as high pressure offshore is expected
to persist through the week. Northerly winds around 15-20 kt will
continue today. Expect periods of winds gusting up to 25 kt
through Friday during the late afternoon and evenings. Including
all coastal waters in the Small Craft Advisory through this
evening 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. /DH

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.PQR WATCHES/WARNINGS/ADVISORIES...
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OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ251-
     271.
     Small Craft Advisory until 11 PM PDT this evening for PZZ252-
     253-272-273.
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&&

$$

www.weather.gov/portland

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