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Area forecast discussion 
National Weather Service Portland or
858 PM PDT Mon Aug 29 2016

Synopsis...an upper trough will move through Tuesday which will
bring rain showers to areas west of the Coast Range and the
potential for thunderstorms in the Lane County Cascades. Shower
chances will remain for the remainder of the week with the best
chances in the north Oregon Coast Range and Willapa Hills.

&&

Update...marine clouds pushing inland from the coast will reach much
of the Willamette Valley by Tuesday morning. With clouds overhead and
dewpoints in the 50s, temperatures will only drop into the 50s once
again tonight, likely struggling to drop below 60 in the Portland
Metro. Will see some drizzle along the coast and possibly in the
Coast Range tonight through Tuesday morning. Overall, forecast looks
like it is on track with only minor sky cover changes with the
evening forecast update. Bowen

Short term (previous)...marine stratus should be quite successful
with its inland push tonight as a wave located near 38n and 135w
lifts towards the area and increases onshore flow. The added lift
associated with this system will be enough to squeeze some drizzle
out of the marine layer for areas west of the Coast Range. Focus
during the day Tuesday will shift to the potential for thunder in the
central Oregon Cascades. While instability appears relatively weak,
sufficient lift ahead of a quick moving wave may be enough of a
catalyst for an isolated rumble of thunder. This threat will come to
an end rather quickly as the wave quickly moves NE of our area by
00z.

Along the coast, persistent shower chances will remain through the
short term period as several weak waves move through the flow. The
strongest of these waves will push through during the day on
Wednesday where pops have now been increased to 70-80% over the north
Oregon Coast Range and Willapa Hills. /Bentley

Long term...no changes. Previous discussion follows...chance pops
remain for the remainder of the week and into the weekend as the long
wave trough axis waits until late in the weekend to shift east of the
Pacific northwest. Both the European model (ecmwf) and GFS agree on the arrival timing of the
upper low Thursday night, but they differ in intensity and speed. The
European model (ecmwf) remains more progressive and shifts east quickly while the GFS
slows down and cuts off an upper low over Washington. The latter
solution will definitely be more wet than the former, but until
models come into better agreement, have kept pops in the 30-50% range
during the period. /Bentley

&&

Aviation...MVFR marine stratus will continue along the coast
tonight and most of Tue, with patchy IFR cigs and vsbys over the
central coast. The interior will remain VFR under passing high
clouds through late tonight. Expect a solid marine push overnight
with MVFR cigs developing in the interior between 10z and 12z.
While inland cigs should lift to VFR and begin to thin around 18z,
clouds will be more stubborn around the coastal areas and the
extreme lower reaches of the Columbia River. An approaching front
will bring a chance of rain starting Tue night.

Kpdx and approaches...VFR under passing high clouds through late
tonight. Expect MVFR stratus deck around 2500 ft to arrive by
around 12z, persisting through around 17z before lifting and
eventually scattering by late morning or midday. /64/Cullen

&&

Marine...no changes. Previous discussion follows...south winds
continue across the waters this afternoon, but generally remain
around 15 kt. A few gusts near advisory criteria may occur over
the far outer coastal waters (beyond 35 nm from shore) this
evening, but these are not expected to be frequent or widespread
enough to warrant an advisory. Stronger gusts possible later
Tuesday as a weak front reaches the waters. Will hold off on an
advisory for now, but may end up needing a short advisory for
winds over the outer waters. Winds will vary between south and
southwest for the remainder of the week as a few more weak fronts
reach the waters. Then stronger north winds return over the
weekend as high pressure rebuilds over the NE Pacific and a
thermal low builds up the Oregon coast.

Seas will remain generally 4 to 6 feet through much of the week,
largest during the periods of gustier winds. Seas are a mix of
long period (14 second) south swell and northwest swell at around
8 seconds. Cullen

&&

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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