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Area forecast discussion 
National Weather Service Portland or
314 am PDT sun Aug 31 2014

Synopsis...clouds...cooler temperatures...and a few lingering
showers today on the backside of a departing trough. There will be
slight warming Monday with dry weather as a weak upper ridge moves
over the region. Another upper level trough will bring a return of
cloudy and cool weather Tuesday and Wednesday. Offshore winds and
warmer temperatures expected late in the week.

&&

Short term...today through Wednesday...water vapor imagery shows the
Pacific northwest sandwiched between an upper ridge over the east Pacific
and an upper trough over the inter-mountain west. Radar imagery shows
weak echos off shore and isolated showers are possible for the
coast...Coast Range and Cascades early this morning. Infrared imagery
shows areas of middle-level clouds offshore that will move over northwest
Oregon throughout the day...and help maintain seasonably cool weather
today.

The upper jet that helped produce lift over northwest Oregon on Saturday
has shifted to the north...resulting in a drier northwesterly flow
for the region. The storm track is also further north...such that the
approaching shortwave troughs embedded within the northwest flow...will
remain north of the Portland forecast area the next couple of days.
Therefore the shortwave that was expected to bring rain tonight and
Monday to the Portland forecast area will most likely not produce any
rain over northwest Oregon. Have therefore reduced probability of precipitation for tonight and
Monday across the region.

Weak upper level ridging will attempt to build in Monday...and the
daytime temperatures will warm closer to the seasonal normals. This
warming will be short-lived as another upper trough dropping south
from the Gulf of Alaska will bring additional cloudy and seasonably
cool weather for Tuesday. Most of the showers with this trough will
remain in central and northern Washington...but there may be a few
light showers across SW Washington Tuesday evening. Otherwise...a
deep marine layer will likely result in marine clouds pushing far
inland Wednesday morning.Tj

Long term...Wednesday night through Saturday...the upper trough
moves inland Wednesday night. An upper level ridge noses into western
Canada and northern Washington Thursday...but a low off of California
will maintain lower pressure over northwest Oregon. High pressure to the
north and east...with low pressure to the south and southeast will
result in offshore winds across the Portland forecast area. Expect
and increase in sunshine and afternoon temperatures Thursday through
next Saturday. Tj

&&

Aviation...weak pressure gradients across western Oregon and a
moist...but relatively unstable lower atmosphere should generally
keep conditions VFR inland...with periods of IFR and MVFR conditions
along the coast. However...there should be a period of VFR conditions
along the coast this afternoon...but timing and duration remains
uncertain. There is also a chance MVFR conditions will develop for
a few hours centered around 15z this morning...but confidence is low
at this point. Otherwise...additional IFR conditions will likely
redevelop along the coast Sunday night...but inland penetration
should be limited.

Kpdx and approaches...there is a chance MVFR conditions will develop
for a couple hours around 15z Monday...but otherwise...expect VFR
conditions through 12z Monday. /Neuman

&&

Marine...high pressure today will give way to a weakening front
on Monday. Few marine impacts are expected. High pressure will
then return to the northeast Pacific with thermal low pressure
strengthening over interior northern California. This will place
the waters in a familiar this Summer with periods of gusty northerly
winds. Expect seas to fluctuate generally between 4 and 7 feet with
the predominant swell remaining around 9 to 10 seconds out of the
northwest this week. /Neuman

&&

Pqr watches/warnings/advisories...
or...none.
Washington...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. The area is
commonly referred to as the forecast area.

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