Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 290405

Area Forecast Discussion
National Weather Service Portland OR
905 PM PDT Sun Aug 28 2016

.SYNOPSIS...An upper trough off British Columbia will continue
tonight and early Monday, then dig south along the coast Monday
night and Tuesday, then swing onshore during the latter part of the
week. This will maintain onshore flow over the local area for at
least night and morning low clouds and cooler temperatures. Expect
showers especially Tuesday night and beyond.

.SHORT TERM...Tonight through Wednesday...An upper low was off the
British Columbia coast this evening with southwest flow aloft that
will maintain onshore flow across southwest Washington and northwest
Oregon. Low clouds cleared back offshore this afternoon except along
the central Oregon coast, and this nose of low clouds is beginning to
move north and expand onshore this evening. As a result, have slowed
down the arrival of the low clouds and patchy fog and local drizzle
along the north coast overnight, as well as the clouds inland Monday
morning compared to the model forecasts and our previous forecast.

This upper low will dig south along the coast, especially Monday
night and Tuesday, which should increase the low cloud coverage
Tuesday morning. In addition, the weak low off the California is
forecast to get lifted north through central and eastern Oregon
Tuesday and Tuesday evening. This could brush the higher Oregon
Cascades with a few showers or thunderstorms Tuesday and early
Tuesday evening.

Farther west, after some local drizzle along the coast Monday and
Tuesday, the models indicate a modest front will move onto the coast
Tuesday night and then inland Wednesday as the front weakens and
lifts out to the north. There is a decent chance a good part of our
forecast area will see some light precipitation from this feature. We
may see some light breezes along the coast as well.

Temps will still be around or just above 80 Monday, fall into the 70s
Tuesday, and then closer to 70 Wednesday. Tolleson

.LONG TERM...No Changes. Previous discussion follows...
Wednesday night through Saturday...Continued cooler and cloudier with
periods of light rain will be the general rule for the second half of
next week as various impulses rotate across the region around the
base of the mean trough to the north. However, timing and strength
differences remain among the forecast models with a fair amount of
spread among ensemble members. As a result, less confidence in the
precise periods of higher chances of rain. Regardless, afternoon high
temperatures will remain in the low 70s inland during the extended
period, several degrees below normal for this time of year. With cool
and moist conditions, it will feel like an early taste of fall.
However, overnight low temperatures will be more seasonable, in the
50s.  Bowen/Cullen

.AVIATION...Conditions generally VFR across the forecast area this
evening except for portions of the central coast south of KONP. MVFR
marine stratus will continue to solidify along the central coast over
the next couple of hours, with a period of IFR stratus possible
overnight. Low stratus is expected to build northward up the coast
tonight reaching KAST around midnight. Marine layer will once again
push inland overnight, but not expecting any reduced cigs in the
interior except for some patchy stuff in the far south valley. Any
stratus that forms in the interior will dissipate by late Mon
morning. Reduced flight conditions look to continue along the coast
Mon afternoon/evening.

KPDX AND APPROACHES...VFR tonight and Mon. Could see some patchy low
stratus develop along the Columbia River early Mon morning, but not
expecting any reduced flight conditions. /64

.MARINE...No changes. Previous discussion follows...Benign marine
weather concerns this week. Models have come to a better agreement
that winds will remain mostly out of the south through the week and
even into next weekend. A period of stronger gusty winds is possible
on Tuesday ahead of a cold front that will move through Wednesday
night, but otherwise no small craft for winds concerns across our

Seas will remain 5 feet or less through the weekend due to light
winds and a lack of any significant storm systems in the north
Pacific. /Bentley



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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.