Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 290945
Area Forecast Discussion
National Weather Service Portland OR
245 AM PDT Fri Jul 29 2016
.SYNOPSIS...Weak upper ridging will maintain very warm inland
temperatures today. An upper level trough will increase night and
morning clouds and cooler temperatures this weekend. Brief high
pressure will move over the area Monday before another upper low
impacts the clouds and temperatures Tuesday and Wednesday.
.SHORT TERM...(Today through Monday)...Weak high pressure holds over
the area today and will limit the inland movement of marine clouds
this morning. Satellite imagery shows low clouds along the coast have
pushed into some of the coastal valleys of the coast range and up the
lower Columbia river valley early this morning. Do not think that the
low marine clouds will move much further inland this morning and will
likely stay west of kelso.
Valley temperatures (east of the coast range) are starting 5 or so
degrees warmer this morning than they were 24 hours ago. This
combined with the absence of inland marine clouds will lead to
another very warm day today with temperatures this afternoon very
similar to yesterday (Thursday). 500mb heights begin to lower this
afternoon and evening as an upper level trough approaches from the
northwest, but think the lowering heights will have little influence
on todays temperatures.
The marine layer will deepen tonight as the upper level trough nears
the Pacific northwest and the marine clouds will move further inland
Saturday morning, especially to the north. THe trough may also
produce drizzle along the Washington and North Oregon coast Saturday
morning. Daytime temperatures will cool closer to the seasonal
normals Saturday afternoon.
An even deeper marine layer is expected Saturday night with marine
stratus likely reaching the Cascades Sunday morning. Patchy drizzle
swill return to the coast and possibly push inland to areas along the
Columbia River. Seasonally cool weather will persist. There will be
brief weak ridging Monday as the area will be between two upper
troughs, and the marine stratus should stay west of the Cascades.
Otherwise there will be little change in the sensible weather Monday.
.LONG TERM...(Monday Night through Friday)...No changes. Previous
discussion follows...Models are coming into better agreement on an
upper low moving through Washington on Monday night and Tuesday. It
appears this low will drop far enough equatorward to bring the
potential for rain showers for northern Oregon and southwest
Washington. Therefore, introduced a slight chance PoP for these
northern areas Monday evening. Was hesitant to go much higher with
the PoPs as there has been a tendency for these waves to be less
amplified/further north through time and would not be surprised if a
similar trend begins with this wave. With that being said, with
models in good agreement on timing and strength of the wave, felt a
slight chance was justified. Do expect diurnal cu development along
the Cascade crests on Monday afternoon, but with a fairly shallow
convective cloud depth, do not anticipate any showers to develop.
Shortwave ridging will build in behind this low and bring fair
weather for the middle portion of next week. Beyond this, fair
weather will prevail for the remainder of the long term period.
ECMWF/GFS/GEM are all hinting at another upper low dropping down the
BC coast towards next weekend, but considerable differences remain
with regard to the timing and southern progression of this system.
.AVIATION...IFR stratus to persist at the coast through the early
morning hours. Clouds should burn back offshore by mid-to-late
morning, with mainly VFR at the coast through the rest of the day.
IFR stratus will push back into the coast again this evening. VFR
conditions will persist inland for the next 24 hrs.
KPDX AND APPROACHES...VFR through tonight. NW winds gusting to
around 20 kt during the late afternoon and early evening. Pyle
.MARINE...Surface high pres remains over the NE Pac with a thermal
low over the N Calif and S Oregon coast through the weekend and
much of next week. This will continue the pattern of gusty
northerly winds through tonight. The strongest winds will be over
the central Oregon waters, where winds may gust to 30 kt this
afternoon and evening. A small craft advisory is in effect for all
but the northern inner waters through 12Z Sat. Winds will weaken
slightly on Sat and even more on Sun as the NE Pac high weakens.
With north winds continuing for the next few days, seas will
continue to be dominated by steep locally generated seas. Will need
to hang on to the small craft for hazardous seas through Fri night
for the northern and outer waters due to square seas in the range of
7 to 9 feet. Locally driven wind waves will start to subside Sat as
wind speeds diminish, but a fresh swell from the nnw will keep seas
PZ...Small Craft Advisory for winds until 5 AM PDT Saturday for
Coastal waters from Cascade Head to Florence OR out 10 nm-
Waters from Cape Shoalwater WA to Florence OR from 10 to
Small Craft Advisory for hazardous seas until 5 AM PDT Saturday
for Coastal waters from Cascade Head to Florence OR out 10
nm-Waters from Cape Shoalwater WA to Florence OR from 10
to 60 nm.
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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.