085
FXUS66 KPQR 052117
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
210 PM PDT Fri Jul 5 2024

.SYNOPSIS...Strong high pressure over the western USA will maintain
hot days and warm nights into next week. Warmest days will be Sunday
and Monday, with many inland temperatures reaching near 105 deg.
Even the coast is warm, with highs in the upper 70s to mid 80s today
and again Saturday. But, cooler ocean air will spread onshore along
the coast later Saturday, with more pleasant temperatures for Sunday
into next week. But, area from Coast Range to the Cascades will have
to wait until late Tue and Wed for a slow cooldown to start.
&&

.DISCUSSION...(tonight through Wednesday)...not much in way of
change, as strong high pressure remains anchored along the west coast
of the USA. This will maintain hot afternoons/early evenings, with
warm nights for this weekend into early next week. Already today,
temperatures were in the upper 80s to lower 90s by 1 pm. Not a good
omen, as look on track to reach 100 deg in the Willamette Valley and
Columbia River Gorge. Even along the normally cooler coast,
temperatures on Friday afternoon climbed into the middle 80s, with
temperatures closer to 90 into the nearby coastal river valleys of
the Coast Range.

As for Saturday through Monday, will see pattern continue, with hot
afternoons/early evenings, with temperatures reaching 100 to 105 deg
for most interior lowlands, but in the middle 80s to middle 90s in
the Cascades and the Coast Range/Willapa Hills. But, with thermal
trough over the region, will not see all that much in way of winds.
So, will feel rather hot. At least humidity will be down, with
afternoon minimums of 15-25%. But, this comes with a price. With hot
temperatures and low humidity, one can easily become dehydrated. So,
everyone should keep hydrated to avoid more serious injuries from
heat, as well as avoiding more strenuous activities between 11 am and
6 pm. Got animals? Consider if they have adequate shade and water,
and perhaps consider taking them out earlier in the day or in the
evening as it starts to get a bit cooler.

Speaking of cooling, it will take some time for temperatures to fall
in the evenings. Many lowlands areas may not see temperatures drop
back under 90 until 8 pm (especially in more urban areas). Overnight
lows will fall back to the upper 50s to middle 60s for many areas,
but, does appear will generally stay the warmest in the urban areas
where overnight lows will stay in the upper 60s to lower 70s. As
such, may take a while for any refreshing coolness to take hold, and
that may be not until 2 or 3 am.

Will see an uptick of onshore flow Saturday night, enough to drop the
coast back to more pleasant temperatures for Sunday. This onshore
flow may be enough to knock down morning lows a bit. But, air mass
remains dry and warm, so this so-called coolness will be fleeting.
With the thermal trough sitting over the Willamette Valley on Sunday,
will see another hot day on Sunday, but with lighter winds. Bit
cooler along the coast, with highs in the 70s to middle 80s along the
coast for Sunday into early next week.

Again, will have hot afternoon/early evening temperatures across the
region (away from immediate coastal areas) into early next week. As
such, the duration of the heat will be memorable. For the Willamette
Valley, the record most days in a row of 100+ deg is 5 days, set in
mid-July 1941 at Portland airport. Many areas in the Willamette
Valley/Clark County have seen 4 days in row a few times, such as back
in August 2023, or 2015 or in 1981. This year, it looks like 4 days
of 100+ deg heat is a good bet, but will see if the record 5 days is
reached. A lot will depends on temperatures on Tuesday. Current
thoughts are that will have last hot day on Tuesday (across the
interior).  As such, will extend the current Excessive Heat Warning
and Heat Advisory through Tuesday evening.

Warmest day looks to be the 8th of July (Monday). Highest potential
of the the highest heat looks focused on areas around the
Portland/Vancouver metro and then to the east (through the Columbia
Gorge) and to the south (throughout the Willamette Valley).

What are the odds of reaching 100+/105+ deg at select cities, based
on data as of Friday morning:

        6 Jul        7 JUL        8 JUL        9 JUL
          100  105     100  105     100  105     100  105
  ========================================================
Kelso      35%   1%     45%   5%     50%  20%     80%  20%
Portland*     90%  20%     90%  30%     85%  45%     90%  50%
Salem      90%  40%     90%  40%     80%  50%     85%  45%
Eugene      85%  35%     80%  30%     80%  35%     75%  30%
Hood River    65%   7%     75%  20%     95%  40%     95%  60%

The % of reaching 110 or higher is <5% for all areas, except
     is 5-15% on Monday and Tuesday in the Willamette Valley.

*Portland is for Portland/Vancouver metro area


Will see onshore flow increase Tuesday night into Wednesday, as the
thermal trough shifts east of the Cascades. This will bring back
westerly winds to the west side of the Cascades, with a modest
cooldown  for the interior for Wednesday. Overall, temperatures on
Wednesday look to be in the upper 80s to middle 90s, but even cooler
temperatures for Thursday, as look to stay in the 80s.  /Rockey
&&

.FIRE WEATHER...hot weather will combine with dry and gusty afternoon
northerly winds again this afternoon/evening as thermal low pressure
strengthens over SW Oregon, tightening surface pressure gradients,
especially across the southern Willamette Valley. While fuels today
are not quite ready for our fire weather zones to be eligible for a
Red Flag Warning, the hot and dry weather will rapidly dry out
vegetation over the coming days. Unfortunately overnight relative
humidity recoveries appear poor over the higher terrain for several
nights moving forward, further working to chip away at fuel moisture.
Forecast guidance still suggests winds will be lighter Saturday, but
it will still be very hot, dry, and unstable near the surface with
thermal low pressure overhead.
&&

.AVIATION...Minimal impacts expected with widespread VFR
conditions across the airspace. Calm winds each night will give
way to gusty northerly winds each afternoon (19Z-21Z) through late
evening (05Z-07Z) Gusts up to 25 kt along the coast and gusts up
to 20 kt for inland locations.

PDX AND APPROACHES...VFR with clear skies. Gusty northerly winds
each afternoon (20Z) through late evening (06Z) with gusts up to
20 kt. /42
&&

.MARINE...High pressure over the eastern Pacific paired with a
thermally induced low pressure over California/Southern Oregon and
the Great Basin. This pattern will persist through the weekend
and likely into the start of next week. Therefore, expect Small
Craft conditions across all waters with gusts up to 30 kt. Winds
continue to follow a diurnal cycle, reaching Small Craft Advisory
criteria each afternoon and evening, then decreasing overnight.
Seas will be predominately wind-driven resulting in 4-7 ft at
9-11 seconds.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Excessive Heat Warning until 10 PM PDT Tuesday for ORZ104>125.
     Heat Advisory until 10 PM PDT Tuesday for ORZ126>128.

WA...Excessive Heat Warning until 10 PM PDT Tuesday for WAZ202>210.
     Heat Advisory until 10 PM PDT Tuesday for WAZ211.

PZ...Small Craft Advisory until 2 AM PDT Saturday for PZZ251>253-271.
     Small Craft Advisory until 8 AM PDT Saturday for PZZ272-273.

&&


$$

www.weather.gov/portland

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