NWS Portland, OR wrote its last area forecast discussion before the first event at Aug 6, 7:50 AM PST, 3 hours 10 minutes earlier.
Area forecast discussion, Aug 6, 7:50 AM PST, 3 hours 10 minutes before
Area Forecast Discussion
National Weather Service Portland OR
850 AM PDT Mon Aug 6 2018
.SYNOPSIS...High pressure will maintain hot temperatures inland, with
hazy conditions through Thursday. Stays cooler along the coast, with
variable marine stratus. Upper low will pass to our north later in
the week, bringing cooler marine air inland, along with more
seasonable temperatures for Friday, and into next weekend.
&&
.SHORT TERM...Today through Wednesday...Made minor changes to today's
sky cover and temperatures this morning, otherwise the forecast looks
on track for hot and dry weather. Clouds across the interior this
morning should clear later this morning with temperatures rising
similar to slightly warmer than yesterday (Sunday) afternoon. Hazy
and smokey skies are expected as wildfires to the south continue to
produce smoke, and the interior winds remain relatively light. Most
of the smoke will be higher in the atmosphere and have little impacts
at the lower levels. The smoke will be most noticeable in the
Cascades of Lane County.
Will take a closer look at temperatures Tuesday through Thursday this
afternoon and issue any necessary heat related products as triple
digit high temperatures are looking more likely for the interior
valleys. ~TJ
From previous discussion sent at 305 AM this morning...Light onshore
gradients this am, with marine stratus and patchy fog and drizzle
along the coast. These clouds will take time to break, likely later
this am into early afternoon. Now, the stratus has pushed through the
Coast Range valleys to the interior. However, think will not be as
extensive as that seen Sunday morning. This would bring stratus up
the Columbia River into Clark County, possibly to near Portland this
am, as well as pockets in the south Willamette Valley. Any inland
clouds will burn off by 9 or 10 am.
Mid and upper level winds turned southerly during the day on Sunday.
This has allowed rather extensive areas of haze and smoke aloft from
southern Oregon and northern Calif wildfires to spread north across
all of northwest Oregon and southwest Washington. Most to the thicker
smoke generally confined to layers between 4000 and 7000 feet above
the ground. So, smoke most affecting higher elevations in the
Cascades.
Not much change in the overall weather pattern for today through Wed.
Low pressure will sit well offshore, while high pressure persists
over the Great Basin into the Pac NW. This will maintain very warm
air mass over the region. Will see max temperatures into the lower
90s inland today. But, air mass will stay quite warm for Tue and Wed,
with hot conditions in the afternoons and evenings. Highs both days
likely to be in mid to upper 90s, with some spots reaching or just
above 100 deg. As usual, tad cooler in the coastal mtns, and much
cooler along the coast where highs will stay in the upper 60s to 70s.
Overnight temperatures may take some time to cool, thanks in part to
the variable haze/smoke aloft. Some areas, especially larger urban
areas, may take until 3 or 4 am Tue and again Wed to get under 70
deg, and then only down to the mid to upper 60s. So, will see some
warm nights coming up this week.
Likely will need a heat advisory or heat warning for Tue and Wed.
But, will let day shift re-evaluate this potential. /Rockey
.LONG TERM...No Changes. Previous discussion follows...Wednesday
night through Sunday...Models are in general agreement that heat will
continue Thursday as the ridge strength and temperatures look like
they'll peak then. The question then becomes what happens with the
low pressure that will have been sitting well offshore all week. The
GFS continues to favor a solution which brings the low inland Friday
and Saturday, which would mean significant cooling and maybe even
some rain. The 12Z ECMWF hedged towards the GFS solution, putting the
two models in better agreement than they have been in previous days
regarding this time frame. However, am still reluctant to hop on
board the progressive solution with a lack of ECMWF run-to-run
consistency and the tendency for heat to stick around longer. Thus,
have chosen to keep the forecast dry and temperatures slightly
warmer, trending toward the model averages for Friday and Saturday.
If the ECMWF sticks with the more progressive solution for another
run or two, will be more inclined to believe it.
The back end of the trough looks like it would still be moving
through on Sunday, likely meaning slightly warmer temperatures than
Saturday, but still not hot. Again, am taking the models with a
couple of grains of salt this far out, so confidence is low in the
forecast details. Bowen
&&
.AVIATION...Upper level high pressures continues to build over
the Pacific Northwest today. IFR conditions continue along the
coast this morning, though some areas of the coast (especially
from KTMK northward) may see scattering and a few hours of VFR
conditions this afternoon/early evening. However, IFR conditions
will return again late this evening through the overnight period.
Inland, a few pockets of low clouds remain along the lower
Columbia River, in the Portland metro area, and in the far
southern portions of the Willamette Valley. These are expected to
gradually scatter by around 18Z. Otherwise, expect VFR conditions
to continue. Smoke from wildfires burning over southern Oregon
and northern California will continue to spread over the region
aloft, but this smoke is unlikely to produce significant visibility
restrictions through the period.
KPDX AND APPROACHES...Few low clouds will scatter out this
morning, so expect VFR conditions through the next 24
hours. Cullen
&&
.MARINE...No changes, and previous discussion follows...An area of
weak surface high pressure will remain near or over the waters for
much of the upcoming work week. This should generally keep winds
light. However, winds will come up a bit Tuesday and Tuesday night
with northerly wind gusts of 20 to 25 kt possible. A large low
pressure system currently spinning near 140W will eventually move
into the Pacific Northwest towards Friday or Saturday, which should
bring a period of gusty southerly winds to the waters. /Neuman
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the CWA or forecast area.