262
FXUS66 KPQR 012301 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
400 PM PDT Mon Jul 1 2024

.SYNOPSIS...Seasonable temperatures will continue through Wednesday
as onshore flow continues. A very strong upper level ridge will then
begin amplifying and moving into the Pacific Northwest beginning on
the 4th of July, peaking in strength July 5-7. Confidence has
increased for a significant heatwave during that time as the
probability for high temps over 100 degrees has increased
dramatically to 60-80% across the interior lowlands.

&&

.SHORT TERM...Monday night through Wednesday night...The short term
forecast is highlighted by an onshore flow pattern with varying
degrees of morning cloud cover, afternoon sunshine, and seasonable
temperatures. In fact, Tuesday is shaping up to be slightly cooler
with high temps generally in the mid to upper 70s across the interior
lowlands and 60s at the coast. Wednesday looks to feature similar
temperatures, albeit a few degrees warmer. As has been the case over
the past several days, northerly to northwesterly surface winds will
increase a bit in the afternoon each day, especially across the
southern Willamette Valley where winds will likely gust up to 20 mph.
This includes the Eugene-Springfield area. Overnight lows each night
look to range between 45-55 degrees, warmest over the Portland metro.
This will offer excellent overnight relief for those without air
conditioning. However, this relief will be short-lived as a
significant heatwave is expected to impact the region from July 4-7,
and possibly even beyond July 7th. This heatwave is discussed in more
detail below.  -TK

&&

.LONG TERM...Thursday through Sunday night...The long term forecast
is highlighted by a significant heatwave with record breaking
temperatures now likely to occur. HeatRisk is now in the moderate to
major category across all of northwest Oregon and southwest
Washington, except for the coast where weak onshore flow looks to
maintain much cooler temperatures when compared to inland locations.
Before getting into the temperature forecast, would first like to
discuss the synoptic scale setup in place. Models and their ensembles
are now honed in on an upper level ridge amplifying over the western
CONUS July 4-7, peaking in strength July 5-7. It appears an omega
blocking pattern will develop during that time due to a closed upper
level low over the northeast Pacific and another over the Northern
Plains into the Great Lakes region. These two lows will help keep the
ridge over the western CONUS locked in place for at least three to
four days, potentially even longer than that.

With this impressive ridge in place, temperatures will become
abnormally hot with record breaking high temperatures now likely to
occur. The latest suite of model guidance continues trending warmer,
with widespread high temps in the lower 100s for most valley
locations away from the coast likely by July 5-6 according to the
deterministic NBM. In fact, the probability for high temperatures
above 100 degrees has increased dramatically to 60-80%. The warmest
ensemble members from the EPS/GEFS suggest high temps close to 110
degrees or warmer, and the NBM is now showing a 15-30% chance for
high temps of 110 degrees or warmer. Regardless of whether high temps
wind up near 100, 105, or 110, it will be more than hot enough for
people to suffer from heat exhaustion or heat stroke if outdoors for
a prolonged period of time, or for people who are indoors with no air
conditioning. This has helped push HeatRisk into the major category
for the entire Portland metro, Salem, Eugene, Columbia River Gorge
and Upper Hood River Valley. A major HeatRisk means anyone without
effective cooling and/or adequate hydration will be impacted,
especially those who are particularly sensitive to heat. Be sure to
do everything you can to stay cool during the upcoming heatwave, and
don`t forget to check on your neighbors and loved ones from time to
time. Lastly, never leave pets or people inside a hot car, and ensure
your pets stay cool during this heatwave as well. Walking your dog in
the afternoon will not be a good idea as their paws may easily burn.
It`s also worth mentioning that overnight lows are looking quite warm
with minimal overnight relief. As of right now, overnight lows will
likely wind up in mid 60s to lower 70s.  -TK

&&

.AVIATION...Marine stratus continues to linger with IFR/MVFR
conditions on the coast, and these lowered conditions are expected
to slowly push offshore/scour out through 20Z Monday. These
conditions are expected to return (50-80% probability) to the
coast around 04Z-07Z Tuesday as a marine push is expected.

Inland locations currently are seeing widespread VFR, with a few
exceptions as MVFR conditions are currently impacting areas north
of KSPB. Locations with lowered flight conditions are expected to
improve to VFR around 20Z Monday. VFR conditions expected to
dominant for inland locations through the remainder of the TAF
period, with the exception of areas north of KSPB as a renewed
marine push, could result in MVFR conditions along portions of the
Columbia River. Could also see some backbuilding clouds off the
Cascades, that could bring MVFR conditions (45%-65% probability)
to KPDX and KTTD starting around 10Z Tuesday.

Inland locations will also likely see northerly gusts up to 20 kt
starting around 02Z Tuesday through 07Z Tuesday.

PDX AND APPROACHES...MVFR conditions will improve to VFR through
19Z Monday. Northerly gusts up to 20 kt starting around 02Z
Tuesday through 07Z Tuesday. Backbuilding clouds off the
Cascades, that could bring MVFR conditions (45%-65% probability)
to KPDX starting around 12Z Tuesday. /42

&&

.MARINE...Weak high pressure over the northeast Pacific with lower
surface pressure over California and the Great Basin will more or
less continue through the week. A weak front is in the process of
passing through, but effects look fairly minimal, with light
northwesterly winds through Monday morning.  Afterwards, expect
NNW winds across the waters as high pressure strengthens toward
the middle of next week, with the strongest winds generally off
the central coast of Oregon and lighter winds farther north. Winds
will generally peak in the afternoon and evening hours each day.
Small Craft Advisory remains on track for the central zones, but
zones further to the north still look fairly marginal. Because as
a thermal low develops along the northern California/southwest
Oregon coast on Tuesday and strengthening/spreading north into
Wednesday and thereafter. As a result will see an increase the
pressure gradient along the coast and over the waters with a >90%
chance that northerly wind gusts of 20-30 kt spread northward
across the waters by mid week. This will in return develop steep
wind driven seas of 5-8 ft with a dominant period of 7-8 seconds
by late Tuesday or Wednesday.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Wednesday for PZZ253-273.
&&


$$

www.weather.gov/portland

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