Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 270402
AFDPQR

Area Forecast Discussion
National Weather Service Portland Oregon
900 PM PDT Mon Sep 26 2016

.SYNOPSIS... A weak front will brush the forecast area late tonight
and Tue with more clouds, onshore flow, and spotty light
precipitation mainly near the coast. The forecast area will be in
between systems during the mid week period. The next low is expected
to affect the area later in the week and on next weekend.
&&

.SHORT TERM...Tonight through Thursday...No changes as all in on
track for a weak dying front to push across the region late tonight
and early Tuesday morning. Not much in way of moisture, but will keep
occasional drizzle on the coast into the coast mountains tonight as
the front draws closer. Clouds push inland later tonight, with spotty
drizzle or intermittent sprinkles from Salem northward, but again
best threat of any moisture will be against the Cascades foothills
and north of Portland. In any shape, rainfall will be a Trace to
maybe a few hundredths at best.

Clouds will break up Tue afternoon as drier air behind the front at
mid levels pushes into the region. Clouds will continue to break up
Tuesday night and Wednesday as we are in between systems. Southwest
flow aloft should keep some marine layer going along the coast for at
least some night and morning fog or low clouds. Inland looks as
though any morning clouds or fog will be patchier and more of the
radiational variety with a decent amount of sunshine during the day.
Temps should be a little above normal Wednesday.

Not much change in the night and morning cloud pattern and weather
Wednesday night into Thursday morning. A rather vigorous upper low
will be setting up off the Washington and Oregon coasts Thursday. The
main effect will be some possible convection late in the day near the
Cascade crest late Thursday into Thursday night, and the cooling
aloft that will lead to slightly cooler afternoon highs Thursday as
compared to Wednesday.   Rockellson

.LONG TERM...(Thursday night through Monday)...Expect increasing
clouds late Thursday night through Friday as the upper level trough
advances south and east into the far eastern Pacific just offshore.
The first round of rain will likely reach the coast by Friday
afternoon, before pushing onshore in the evening. Still some timing
differences for the various impulses rotating through the upper low,
so it remains too early to pinpoint the timing and location of
heaviest rainfall through the weekend, as well as just how much
rain, but alternating periods of steady rain and drier weather with
some lingering showers seem likely through the weekend. Another
disturbance may arrive later Sunday or early Monday. Temperatures
through the extended period will remain well below seasonal normals,
only reaching the lower 60s at best from Friday through early next
week. Snow levels begin quite high (generally above 8000 feet) on
Thursday night, but quickly lower to 5500 feet by around midday
Friday and remain between 5000 and 6000 feet through the weekend.
Cullen
&&

.AVIATION...VFR conditions expected in the interior through late
tonight. Meanwhile, IFR marine stratus returned to the coast this
evening. Marine layer is expected to deepen overnight so not
expecting much LIFR cigs along the coast tonight. Expect coastal
cigs to hover between IFR/MVFR tonight. MVFR cigs are likely to
spread into the north end of the Willamette Valley between 08z
and 12z tonight. There is a chance that MVFR cigs spread down into
the central and southern Willamette Valley after 10z, but
confidence not as high for clouds seeping into areas south of
Salem. Conditions in the interior improve to VFR by 19Z. A few
hours of VFR cigs likely along the coast Tue afternoon and
evening.

KPDX AND APPROACHES...VFR expected through 08z-10z tonight. Marine
clouds expected to seep into the Portland area between 8 and 10Z,
with MVFR cigs likely after 10Z. Conditions improve to VFR by 18Z.
&&

.MARINE...A weak front will continue to move across the waters
tonight. High pressure will strengthen late tonight into Tue. As a
result, north winds will strengthen later tonight with 20-25 kt
winds expected to spread into the far outer waters by daybreak
Tue. Expect gusts up to 35 kt over the outer waters later Tue into
Wed. Winds nearshore will not be as strong and likely remain just
under small craft advisory. Seas will build some and steepen as
the result of the winds, resulting in seas in the 6 to 9 ft range
Tue and Wed. A cold front will approach the area Thu with winds
around 20 kts.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds for late tonight through
late Tue night on all coastal waters from 10 to 60 nm
offshore.

&&


$$

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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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