Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Portland or
902 PM PDT sun Jul 5 2015
Synopsis...hot weather will continue over most of the region through
midweek as a strong ridge of high pressure aloft remains over the
area. The exception is the coastal region...where cooler marine air
will hug the coastline the next several days. An upper low off
California may drift far enough north this week to bring
thunderstorms up the Cascade crest in Lane County. Relief from the
heat may come later this week as the upper ridge breaks down enough
to allow stronger onshore flow.
Short term...another hot day today inland with temperatures not far
from those Saturday...and records at Portland Airport...Vancouver and
Troutdale. Eugene had eased a few degrees Saturday and were similar
today. A southerly wind reversal and low stratus surge occurred
along the coast today and dropped temperatures there a few degrees. Clouds
backed a few miles offshore but are already filling in. The light
southerly flow along the coast is forecast to continue through
Monday into Tuesday morning before the more typical summertime
northwest winds return Tuesday afternoon and evening. As a
result...the coast will remain cooler...and clouds will be slow to
clear in the afternoon and evening on Monday...then fill in rapidly
Monday night and continue into Tuesday.
Otherwise the upper ridge is forecast to remain over the area...
squeezed between an upper low off the California coast and weak
systems passing by to the north in Canada. Expect a fairly status
quo day on Monday compared to today...though we may see a few more
low clouds into Kelso along the Columbia River Monday morning...and
perhaps a few low clouds trying to get close to Eugene. Expect
inland temperatures similar on Monday to those today...at or at most down
one or two degrees. Also...the South Valley will tend to be a few
degrees cooler than near Portland. This pattern of temperatures and clouds
will tend to persist into Tuesday...with not a lot of temperature change
The models suggest there is a small chance of thunderstorms near
Willamette Pass Monday afternoon and evening...and again Tuesday
afternoon and Tuesday night...and this looks reasonable. However...
the models have tended to be too far north with their thunderstorms
coverage the last couple of days so that is not certain.
The low off California is trying to move onshore into California on
Wednesday. This may continue the trend of a gradual increase in
onshore flow...and might ease inland temperatures down a couple of more
degrees...but do not expect any significant relief until possibly
the extended period. Still...the upper ridge does weaken a bit on
Wednesday. The track of the low may pull the thunderstorm moisture
south of our area...but for now will let the continuing slight
chance of late day thunder in the Lane County Cascades ride.
No changes to the heat advisory for now. Tolleson
Long term...no changes. Previous discussion follows...
Wednesday night through Sunday...confidence continues to increase
that Rex block pattern with persistent high pressure over the Pacific
northwest will break down by Friday cooling temperatures late this
week. As the ridge breaks down...expect temperatures to be somewhat
cooler on Thursday with highs around 5 degrees cooler than Wednesday
inland. Cooler marine air moves in Thursday night with morning clouds
on Friday...which will cool high temperatures another 5 degrees for
Friday afternoon. As upper-level trough moves through Thursday and
Friday...there will be a chance for a few showers or thunderstorms in
the Lane County Cascades. Pattern of morning clouds with marine air
over the region will keep temperatures closer to normal Saturday and
Aviation...IFR stratus is beginning to fill back in along the
immediate coast this evening...and will impact the coastal airports
tonight through Monday morning. Some of this stratus may move up the
lower Columbia River reaching kkls early Monday. Some clouds will
seep inland through the gaps along the central Oregon coast...but do
not think they will make it to keug. There may be some partial
clearing along the coast in the afternoon...but SW-west winds should
quickly move stratus back to the coast late in the afternoon or early
in the evening. Inland areas will be VFR. Scattered to broken middle and
high clouds will move over Lane County through Monday.
Kpdx and approaches...VFR will continue through Monday. Tj
Marine...a thermally induced surface trough over the waters is
resulting in light southerly winds over the waters today...with winds
generally less than 15 knots. The thermal trough will weaken Monday
night for light and variable winds Monday night through Tuesday
morning. The surface trough will dissipate Tuesday night and Wednesday and high
pressure over the NE Pacific will shift back over the waters... returning
seasonal northwest winds.
Seas have subsided to around 6 feet this afternoon...and will continue
to subside another foot or so tonight. Seas should remain 5 feet or
lower for much next week. Tj/pyle
or...heat advisory until midnight PDT Wednesday night for central
Columbia River gorge-central Willamette Valley-greater
Portland metropolitan area-lower Columbia-northern Oregon Cascade
foothills-south Willamette Valley-Upper Hood River Valley-
western Columbia River gorge.
Washington...heat advisory until midnight PDT Wednesday night for central
Columbia River gorge-Greater Vancouver area-I-5 corridor in
Cowlitz County-South Washington Cascade foothills-western
Columbia River gorge.
Pz...Small Craft Advisory for rough Columbia River bar from
6 am to 10 am PDT Monday.
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This discussion is for northwest Oregon and southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.