Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 141104
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
303 AM PST Thu Dec 14 2017

.SYNOPSIS...Another chilly morning across the region. Increasing
clouds later today and tonight, as changes begin. A front will push
across the region on Friday, with occasional light rain. Then will
see plenty of clouds for a while, with spotty light rain throught he
weekend, but likely to remain dry to south of Salem. Increasing
southwesterly flow aloft next week will bring a series of fronts into
the region, with rain at times, along with mountain snow.

&&

.SHORT TERM...Today through Saturday..Generally, dry air mass remains
in place over the region today. Offshore flow will continue, though
winds about as strong as seen on Wed. Strongest winds will continue
to be in and around the Columbia Gorge, where easterly winds will
gust 45 to 60 mph. As usual, strongest winds will be in the Gorge to
east of Troutdale. Will see patchy fog in the Cowlitz valley, as well
as from Salem southward to Cottage Grove.

Models seemed to have settled down, and continue to show the front
pushing inland on Fri, with main rain moving across the region later
in the morning through the afternoon. Have boosted PoPs for Fri, and
decided to go with occasional light rain to reflect better character
of what should expect.Even so, 0.05 to 0.15 inch expected, with
heavier amounts over Willapa Hills and south Washington Cascades.

Now, earlier models had hinted at possibility of freezing rain east
of Cascade Locks and into the Hood River Valley. But, now seems
timing will make all the difference. Now feel moisture will reach
that area in the afternoon, after the temperatures have warmed a tad.
So, will remove threat of any freezing rain for the eastern Columbia
Gorge and Hood Valley.

Rain will transition to spotty showers Fri evening, and decrease
later Fri night. A warm front will well offshore Fri night will push
spotty rain back into Washington and far northwest Oregon on Sat and
Sat night. Will keep chance (30 to 50 percent) PoPs for the region,
with highest PoPs over southwest Washington. But would not be
surprised if get no precipitation to south of a Newport to Salem line
dry for Sat. Rockey.


.LONG TERM...Saturday night through Wednesday. Transient shortwave
ridging is quickly replaced by the next disturbance, with
precipitation chances back for at least the northern half of the
area. However, the models quickly begin differ in the evolution of
these disturbances over the weekend. For the first half of next week,
these model differences quickly accumulate to provide for even lower
than typical confidence in the details of the pattern that will
emerge. Nonetheless, utilizing ensemble data, there is broad
agreement in a generally more progressive pattern returning. Have
boosted PoPs and clouds across the region for Tue and beyond.

&&

.AVIATION...Offshore flow pattern in place with strong high
pressure east of the Cascades and weak thermal trough along the
Oregon Coast. Stronger east winds than Wed through the Columbia
Gorge this morning. Winds will ease later in the day, but in the
meantime with gusts around 40 kt for KTTD. Surface winds are
lighter PDX westward, resulting in areas of LLWS especially west
and north of downtown Portland due to the stronger winds above
500-1000 ft MSL. Light winds south of KSLE may allow for some
patchy fog later tonight/early Thu; especially around KEUG.
Otherwise VFR will likely prevail through late tonight.

PDX AND APPROACHES...VFR conditions through 12z Friday. Strong
easterly Gorge winds of up to 40 kt between 500 to 2500 ft MSL
may result in some LLWS at times on western approaches this
morning. The stronger winds extend all the way down to the
surface KPDX eastward into the Columbia Gorge. /mh Weagle

&&

.MARINE...Expect E-NE winds locally gusting 25 kt below gaps in
the coastal terrain, mainly near the Columbia River. Winds in
general should be a bit lighter than that. A weak cold front will
begin to break down the high pressure system this evening, then
move across the coastal waters early Fri morning. NW winds behind
the front may push winds up to SCA criteria later Fri/Fri night,
but it will be very marginal and most likely to impact the
northern waters. Swell energy from the WNW and SW will will
combine with an increasing wind wave component to push seas up to
7-9 ft Thu night/Fri. After a break in the swell Saturday and
early Sunday, swell energy from the Gulf of Alaska will push seas
back up toward 10 feet or slightly higher early next week.
Weagle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until 2 PM PST this afternoon for
     Central Willamette Valley-Lower Columbia-South Willamette
     Valley.

WA...Air Stagnation Advisory until 2 PM PST this afternoon for
     Greater Vancouver Area-I-5 Corridor in Cowlitz County.

PZ...None.

&&


$$

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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the CWA, or forecast area.


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