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Area forecast discussion 
National Weather Service Portland or
920 am PDT sun Jul 24 2016

Synopsis...a weak upper trough will develop near the coast today
with weak westerly flow aloft over the Pacific northwest through
Monday and Tuesday. Expect morning low clouds giving way to afternoon
sunshine and warmer but seasonable afternoon temperatures. A stronger
upper level ridge will build for the second half of the week and
bring inland highs well into the 90s Thursday and Friday, before the
next trough arrives to moderate temperatures next weekend.

Short term...(today through tuesday)...skies have cleared across
most of the forecast area this morning. However, a few pockets of
lower clouds remain along the eastern edge of the Willamette Valley
into the valleys of the Cascade foothills, as well as some of the
river valleys in the Coast Range and near the mouth of the Columbia
River. However, expect these clouds to clear in the next hour or so
this morning with a sunny and warm afternoon in store for the region.
Upper air data from Salem indicate that the 850 mb temperature has
increased from around 12c to nearly 16c from last afternoon to early
this morning, and forecast models suggest that the air mass will
warm a few more degrees by this evening. Expect afternoon high
temperatures in the mid 80s across the interior today.

A weak upper trough will then develop in light westerly flow aloft
later today, and this will persist over the region Monday and into
Tuesday. This may help bring an increased push of marine air the next
few mornings, which will in turn increase the areal extent of low
clouds inland both along the Columbia River and into the interior as
well as through the southern gaps into Eugene. This push may be
sufficiently strong to fill the Willamette Valley around daybreak as
the two bands of clouds converge near Salem. However, the clouds will
be relatively quick to clear back to the coast Monday, for plenty of
afternoon sunshine and temperatures right around seasonal norms. The
push Tuesday morning looks to be a little stronger and deeper, so
expect that the clouds will linger a few hours longer and also limit
some of the heating - particularly across the northern half of the

Long term...(tuesday night through saturday) changes. Previous
discussion follows. A weak upper level ridge will dominate most of
the long term forecast. This will bring the familiar pattern of
morning clouds and afternoon sun, with temps in the interior rising
into the 90s late next week. Some relief is possible late next week
as models continue to show an increase in onshore flow.

It is Worth noting that today's 12z GFS is showing some monsoonal
moisture streaming north on Saturday. If this pans out we could see
some thunderstorms develop in the Cascades, but confidence is low so
will leave it out of the forecast for now. /64

Aviation...patchy stratus is resulting in IFR conditions for the
South Washington and north Oregon coast this morning and MVFR cigs
for areas along the Columbia River and along the Cascade
foothills of the north and central Willamette Valley. These
clouds are shallow and will clear quickly for widespread VFR
conditions by this afternoon. North winds will increase along the
coast today with 20 to 25 kt gusts. The south and central Willamette
Valley will have gusts between 15 and 20 kt this afternoon.

Marine stratus will return to the coast this evening with IFR
conditions tonight. The stratus will likely push into the Willamette
Valley Monday morning from the south and north for MVFR conditions.

Kpdx and approaches...patchy MVFR cigs this morning will clear
quickly revealing VFR conditions through this evening. North to
northwest winds will persist today with a brief period with gusts
to 15 kt late this afternoon. MVFR cigs will return to the
terminal Monday morning around 15z. The stratus will be slightly
deeper than it was this morning with MVFR cigs persisting through
17 or 18z. Tj


Marine...north winds will persist through the week as high
pressure holds over the S Washington and north or waters and low pressure
remains over north California and S or. The thermal trough over California will
expand north in the afternoons and evenings for increased gusty
winds in the afternoons and evenings. Small Craft Advisory winds
south of Cascade Head this morning will expand north this
afternoon and evening. The winds will decrease late tonight for a
brief break in the gusty winds. The winds will increase again
mainly south of Cascade Head Monday afternoon and evening. The
seas will be primarily wind-driven and steep with little influence
of distant-sourced swells. Areas south of Cascade Head may have
brief square seas this evening with seas around 6 ft at 6 seconds.


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for winds from 2 PM this afternoon to
midnight PDT tonight for coastal waters from Cape
Shoalwater Washington to Cascade Head or out 60 nm.

Small Craft Advisory for winds until 3 am PDT Monday for
coastal waters from Cascade Head or to Florence or out 60



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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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