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171
FXUS66 KPQR 080439
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
939 PM PDT Fri Jun 7 2024

Updated Aviation Discussion

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.SYNOPSIS...
High pressure of varying intensity across the Pacific
Northwest will maintain mostly above average temperatures through at
least the middle of next week. Precipitation chances remain low
during this period, but peak across the Cascades late Saturday into
early Sunday and then across coastal areas and southwest Washington
Monday night into Tuesday.

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.SHORT TERM...
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Now through Sunday...
Tonight through Sunday...Models and their ensembles are
in good agreement shortwave ridging and 500mb heights across the
Pacific Northwest will gradually subside through the weekend, which
will result in a gradual cooling trend while still maintaining above
average temperatures across inland portions of northwest Oregon and
southwest Washington.

Water vapor satellite imagery reveals a shortwave ridge extending
from the Desert SW north-northwestward through the Pacific Northwest.
However, an embedded shortwave trough is cutting through the ridge
across Oregon, and will bring a slight chance for thunderstorms this
evening, but for areas mainly east of the Cascades late this
afternoon and evening.

Water vapor satellite imagery also reveals an embedded shortwave
trough near 130W off the California coast. Models and their ensembles
are in good agreement this feature will lift northeastward and bring
increased mid and high cloud cover to the region on Saturday. A
slightly more southerly component to the flow aloft on Saturday will
allow for shower and thunderstorm chances to increase across the
Cascades. At this point, nearly all of the HREF guidance suggests
storms will still remain east of the Cascades so NBM`s low PoPs
(20-30%) and low thunderstorm chances (<20%) seem reasonable. /Neuman


.LONG TERM...Sunday Night through Thursday...
Sunday Night through Friday...The global ensembles are
in good agreement 500mb heights will remain above average early next
week, which will maintain above average temperatures across most of
northwest Oregon and southwest Washington during this time.
Nonetheless, there are approximately 10-15% of the members that drag
a weakening front into the region, which would drop temperatures down
to or slightly below average while producing some light rain across
the northern portions of the CWA late Monday or Tuesday. As we move
into the latter part of next week, the ensembles reveal  uncertainty
in the overall pattern does grow substantially. For example, about
20% of the global ensemble membership drops a shortwave trough into
the region that would result in a much cooler and wetter pattern
across the entire CWA as early as late Thursday or Friday. About 35%
of the ensemble memberships suggests there shortwave trough will drop
close enough to the region to bring rain chances to at least the
northern portions of our CWA as early as Friday. Meanwhile, the
remaining global ensemble membership suggests the area will remain
dry and mild under a shortwave ridge. /Neuman
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.AVIATION...
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Surface high pressure offshore and lower surface pressure
over the Great Basin will lead to a typical summertime northwesterly
wind regime across northwest Oregon and southwest Washington with
predominantly VFR conditions areawide through 06z Sunday. The
main exception to that statement will be along the immediate coast
where upwelling near the coast may allow for low end MVFR or IFR
stratus to develop overnight into Saturday morning. Statistical
guidance probabilities have risen to between 40-70% from Tillamook
southward along the coast. The best chance for sub-VFR conditions
is around KNOP between 9Z-17Z Saturday morning. KAST also has a
chance at sub-VFR conditions but the probability is much lower at
10-20%.

PDX AND APPROACHES...Surface high pressure offshore and lower
surface pressure over the Great Basin will lead to a typical
summertime northwesterly wind regime with VFR conditions through
06z Sunday. -Batz/Neuman
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&&

.MARINE...
Surface high pressure remains anchored over the
northeast Pacific with thermally induced lower pressure residing
over the Great Basin. This will result in periods of northerly wind
gusts exceeding 21 kt through early this evening from Cape Falcon
southward. The current Small Craft Advisory covers this hazard well.
Northerly winds today and upwelling along the coast will bring a 20-
40% chance of a low cloud deck forming along the immediate coast
overnight that could bring locally dense fog to primarily the inner
waters Saturday morning. At this point, confidence is still
relatively low this will come to fruition so will hold off on a
dense fog advisory for now.

Gusty winds will subside a bit earlier overnight than is typical
in these summertime northerly wind patterns as a weak front
pushes into the northeast Pacific and weakens the surface high
pressure. The main impact from this front will be for seas to
temporarily climb back into the 7-9 ft range Saturday night
into Sunday.

Another weak front may brush the waters early next week, but the
probability for winds to rise into Small Craft Advisory thresholds
of 21 kt or more is less than 30%. There is good agreement
northerly winds will strengthen midweek with over an 80% chance
that Small Craft Advisory level wind gusts of 21 kt or more return.
Seas look to respond accordingly and appear most likely to climb
back into the 7-9 ft range during that time as well.

There will be another very strong ebb current early Saturday morning
so expect Rough Bar conditions along the Columbia River Bar for
approximately a 3-hour window centered around the strongest ebb
current. /Neuman

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.PQR WATCHES/WARNINGS/ADVISORIES...
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OR...None.
WA...None.
PZ...Small Craft Advisory from 5 AM to 8 AM PDT Saturday for PZZ210.
     Small Craft Advisory until 11 PM PDT this evening for PZZ252-
     253-272-273.
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&&

$$

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