751
FXUS66 KPQR 061006
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
303 AM PDT Sat Jul 6 2024

.SYNOPSIS...Prolonged heatwave continues for all of SW Washington and
NW Oregon today, with the beaches being just about the only
exception. Strong high pressure aloft will support the hot weather
through Tuesday evening, after which a robust push of onshore flow
should bring temperatures closer to early-mid July norms. Trickle of
onshore flow may bring some cooling into the coastal valleys Sunday,
but inland areas and elevations above 1000 ft are unlikely to feel
significant relief. No rain is in sight through next weekend.

&&

.DISCUSSION...Today through next Saturday...Not a lot of changes made
to the forecast this morning, as NW Oregon and SW Washington remain
within the grip of a prolonged and dangerous heat wave.

Will see pattern continue through at least Monday, 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% for most. 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. Keep in mind
that their paws can burn on hot surfaces like concrete and asphalt;
another reason to take them out during the cooler morning hours.

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, or not at all for some of the hotter
Portland neighborhoods. Elevated terrain will remain warm at night as
well, with some RAWS stations possibly not falling much below 80
degrees each night.

Will see a slight 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 3-4 days
of 100+ deg heat is a good bet, but will see if the record 5 days is
reached. A lot will depend 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 days look to be the Monday and Tuesday. 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).

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

                Sat          Sun         Mon          Tue
               July 6       July 7      July 8       July 9
              100  105     100  105    100  105     100  105
  ========================================================
Kelso      40%   1%   70% 5%   70%  25%     65%  30%
Portland*     85%  20%   95%30%   95%  55%     95%  60%
Salem      95%  50%   95%50%   95%  75%     95%  75%
Eugene      95%  30%   95%40%   95%  50%     90%  30%
Hood River    80%   5%   90%20%   95%  65%     95%  85%

The % of reaching 110 or higher is <5% for all areas, except
     is 5-20% on Monday and Tuesday in the Willamette Valley.

*Portland is for Greater 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. Latest WPC
cluster analyses suggest a 70-80% chance of positive 500 mb height
anomalies lingering through next weekend, which would tend to keep
the marine layer on the shallow side and limit the effectiveness of
onshore flow to bring cooling east of the Coast Range. Therefore,
don`t expect temperatures to fall back below seasonal normals anytime
soon.  Rockey/Weagle

&&

.FIRE WEATHER...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 today and
Sunday, but it will still be very hot, dry, and unstable near the
surface with thermal low pressure overhead. Those working
out on the line any day through Tuesday should pay special attention
to staying hydrated, as the expected conditions can easily cause
heat-related illness or worse.Weagle

&&

.AVIATION...High pressure with northwest flow aloft leading to
clear sky VFR conditions through the period. Diurnally driven
winds will be somewhat lighter on Saturday as the ridge axis
shifts closer to the coast and relaxes the gradient, but 10-15 kt
NW winds are still likely to develop at the coastal terminals
after 18z Sat.

PDX AND APPROACHES...VFR with clear skies through the period.
Northwest winds will be lighter around 5-7 kt on Saturday. /DH

&&

.MARINE...High pressure over the waters is expected to weaken
today as an area of low pressure well offshore lifts northward.
Thermally induced low pressure remains over southern Oregon into
California, maintaining northerly winds across the coastal waters.
This will lead to weaker pressure gradients over the weekend with
wind gusts up to 20 kt. Therefore, will allow the Small Craft
Advisory to expire this morning. High pressure is expected to
build over the waters again on Monday with SCA level winds likely
returning by the afternoon. Seas will be predominately wind-
driven resulting in wave heights below 6 ft through early next
week. /DH

&&

.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 early this morning for
     PZZ251>253-271.

     Small Craft Advisory until 8 AM PDT this morning for PZZ272-273.
&&

$$

www.weather.gov/portland

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