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Area forecast discussion 
National Weather Service Portland or
907 am PDT Sat Jul 23 2016

Synopsis...weakly cyclonic northwest flow aloft will maintain some
onshore flow under weakly rising 500 mb heights today. A weak upper
trough will develop near the coast Sunday and remain over the region
Monday and Tuesday, bringing slight cooling and increasing low
clouds inland Monday and Tuesday mornings than on Sunday morning,
along with some patchy morning drizzle along the coast. After
Tuesday, upper ridging will bring warming from Wednesday through
Friday, with highs inland likely reaching well into the 90s Thursday
and Friday.


Short term...(today through monday)...weak west to northwest flow
aloft this morning has maintained a fairly deep marine inversion over
the region. Plenty of clouds over the northwestern third of the
forecast area - north of roughly Florence to Salem to Timothy Lake
line - but these are rotating and spreading south so may yet see a
more solid cloud deck across the southern Willamette Valley this
morning. Also have some lower clouds banked against the Lane County
Cascades and foothills that will gradually erode in the next hour or
two. With weak subsidence today and building 500 mb heights, expect
to see a clearing trend this afternoon. With the warming air mass,
temperatures inland should reach a few degrees warmer this afternoon
than yesterday. Also maintained a mention of patchy light drizzle
along the northern Oregon coast through the morning, but not
expecting any measurable amounts.

Expect some lower clouds to redevelop along the coast and perhaps a
weak push along the Columbia River late tonight and early Sunday,
though likely shallower and less extensive than today. With fewer
clouds, expect inland temperatures to increase a few more degrees on
Sunday - into the mid 80s. A weak upper trough developing on the
coast Sunday will increase onshore flow later in the day Sunday with
a decent surge of low clouds inland both along the Columbia River and
also through the southern coastal gaps into the southern Willamette
Valley for Monday morning. Cullen

Long term...(monday night through friday)...the weak saggy/baggy
upper trough lingers over southwest Washington and northwest Oregon
on Tuesday, and the models suggest Tuesday will be the coolest day of
the week with highs near or slightly below normal with some patchy
drizzle near the coast. After that, the upper ridge rebuilds, peaking
Thursday and Friday, with highs into at least the low to mid 90s
inland. The models suggest onshore flow may redevelop next weekend
for a bit of relief. Tolleson


Aviation...generally VFR across the area at 15z, except for areas
of MVFR cigs in southwest Washington and likely west slopes of the
Oregon Coast Range and north Oregon Cascade foothills. Expect VFR
to develop in the aforementioned areas by early afternoon. Marine
layer tonight through Sunday morning should be less deep, thus a
better chance for MVFR cigs along the South Washington and north
Oregon coast overnight and likely pushing up the Columbia River to

Kpdx and approaches...VFR conditions through 12z Sunday. 12z ksle
sounding and metars show the top of the marine layer around 4000
ft mean sea level. Marine layer to dissipate by noon. Likely to have some
gusty northwest wind late this afternoon into the evening hours.


Marine...not much change to the current forecast. Main marine
issue will be wind. Latest model guidance shows boundary layer
speeds up to 20 kt across pzz255 and pzz275 this afternoon. Will
maintain the Small Craft Advisory for wind across those zones.
Guidance also suggests Small Craft Advisory wind conditions will
spread into the north waters Sunday. Will likely go with an
advisory there in the afternoon forecast. May not need a small
craft Wind Advisory Monday as models show a weak impulse moving
north of the area, deepening the marine layer.

Overall wave heights to hover in the 4 to 5 foot range through
early next week. Highest wave heights over the south waters where
wind waves are larger. As is typical for this time of year, sea
state to be dominated by wind wave and/or fresh swell. Wave
heights show a steady increase the latter half of next week,
possibly reaching 7 to 8 feet. Weishaar


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for winds from 3 PM this afternoon to 2 am
PDT Sunday for coastal waters from Cascade Head or to
Florence or out 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.

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