Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 260959

Area Forecast Discussion
National Weather Service Portland OR
257 AM PDT Thu May 26 2016

.SYNOPSIS...Onshore flow with threat of showers will continue today
into Sunday, with highest chance of showers being on Friday. Appears
may see a dry day on Monday, with temperatures close to seasonable
levels. Appears will see dry and warmer weather next week as high
pressure builds over the region.

.SHORT TERM...(Tonight through Saturday)...Not a lot of change in the
overall pattern for next few days. A deep marine layer remains
entrenched across northwest Oregon and southwest Washington with
plenty of clouds across the region. Combined with the onshore flow,
will see areas of drizzle across on the west and northwest slopes of
higher terrain this am. Also, a weak upper level disturbance moving
over the region today will keep a 20 to 30 percent chance of showers,
though best threat will be over the Coast Range north of highway 6
and the Willapa Hills.Overall, today will be a lot like yesterday,
with clouds very slowly breaking apart later in the afternoon, and
temperatures mostly in the upper 50s to middle 60s.

Next system now over the Gulf of Alaska. Models have been persistent
in sliding this system inland over the Pacific NW on Friday and on
into the northern Rockies Saturday and Sunday. Will keep overall
forecast similar to past trends, with decent threat of showers over
the region on Friday and Friday evening, though best threat will be
north of a Tillamook to Santiam Pass line. Plenty of clouds on Friday
so temperatures may have a hard time getting out of the 50s on the
coast and foothills of the Cascades, while likely on in the lower 60s
over the interior lowlands.

Once the Friday system moves east of the region, will see rather
zonal flow off the Pacific into the Pacific NW. This will maintain
plenty of clouds over the region. Problem is that will still have a
few weak disturbances embedded in the flow, with one moving across
our area on Saturday afternoon. So, even though may see some breaks
in the clouds on Saturday, seems will also have some showers around
the region. Will keep a chance of showers in the forecast for
Saturday into Saturday evening. Areas to south of Salem will have
least threat of showers, and perhaps may escape all showers on
Saturday. But due to some uncertainty, will keep a slim chance of a
showers for those areas.

.LONG TERM...Saturday night through Wednesday...While still some
uncertainty concerning the depth and precise strength of the upper
low, confidence continues to increase that the upper level low
moving south from B.C. over the weekend will take a more inland
track. However, with the upper level trough remaining over the
region on Sunday, a reinforcing shortwave will bring the potential
for some showers across the area. By late Sunday into early Monday
the trough shifts east as a upper ridge near 135W amplifies and
heights begin to rise over the region. Maintained a slight chance
PoP across the extreme northern coastal zones as well as portions of
southwestern Washington for Monday, but suspect that Monday will be
largely dry and warmer, back to near or a few degrees above seasonal
normals. As the upper ridge strengthens and moves over the region
during the early part of next week, expect temperature to further
warm - possibly nearing 80 degrees inland on Tuesday and Wednesday.
However, some differences emerge in the forecast models by midweek
with the GFS suggesting a slightly cooler pattern, so confidence is
only moderate for the end of the long term period.    Cullen

.AVIATION...Cloud deck near 035 MSL is filling in across the
forecast area this morning, with tops around 050-060 MSL. Expect
CIGs to lower a bit over the coming hours; KEUG is already
reporting a BKN019 layer shortly after 08z. More areas of MVFR
will develop toward sunrise, yielding a mix of VFR and MVFR across
the forecast area between 12z-18z. Likely exception will be along
the coast, where areas of -DZ or -RA could result in some patchy
IFR this morning. Improved mixing during the day should allow
conditions to improve after 18z, with some MVFR in showers but
otherwise VFR prevailing during the afternoon.

PDX AND APPROACHES...Solid cloud deck near 3500 ft will persist
through the morning hours, possibly dipping just below 3000 ft at
times as NW winds ease 12z-18z. Some breaks could develop during
the afternoon, but there will also be localized MVFR in isolated
afternoon -SHRA...especially near the Cascades. Light to moderate
W-NW flow expected to prevail through the afternoon.  Weagle

.MARINE...Finally decided to cancel the SCA for winds this
morning as Buoy 46089 remains near 15 kt with gusts to 20 kt. The
buoy report is echoed by a 04z ASCAT pass, which showed NW winds
near 15 kt as well. A couple gusts to 25 kt still cannot be ruled
out for our far NW waters, but these should be too few and far
between to warrant an SCA.

Overall, expect little change in the big picture of our weather
pattern through Saturday. High pressure will remain anchored over
the NE Pac, while a trough of low pressure remains over British
Columbia. A series of weak disturbances will slide down the BC
coast, brushing the Pac NW coastal waters. 00z/06z NAM develop one
of these disturbances into a weak surface low and front Fri night,
which will likely cause winds to back southerly across much of our
waters by Sat AM. Gusts up to 25 kt are shown by the 06z NAM along
the WA/far N OR waters Saturday, so a SCA for wind may eventually
be needed. Seas will remain fairly benign through the weekend;
generally 4-6 ft, primarily comprised of fresh NW swell and/or
wind wave. Strong ridge of high pressure is expected to build
across the waters early next week, with a thermal trough building
up the coast from CA. This should eventually induce some gusty N
winds for the Central/Southern OR waters by Tuesday.  Weagle




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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. is the U.S. government's official web portal to all federal, state and local government web resources and services.