Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 221051
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
245 AM PST Wed Nov 22 2017

.SYNOPSIS...Wet and unsettled weather will continue this week.
A front will drift south as a weak cold front today for more rain,
especially near the coast and in the north interior areas. Snow
levels in the Cascades will remain relatively high. A better defined
cold front sweeps across on Thanksgiving with snow levels in the
Cascades lowering close to, but likely remaining above the passes
Thursday night and Friday. Showers linger Friday before the next
system arrives on the weekend with rising Cascade snow levels. Snow
levels lower back near the Cascade passes again Sunday night and
Monday.

&&

.SHORT TERM...Today through Friday...On the large scale, a stream of
moisture from the tropics arching from around 138W to the PacNW is
being squeezed between high pres of the CA coast and a trough in the
NE Pacific. 850 mb wind of 40-50 kt is efficiently pumping the
moisture toward the PacNW.  Satellite precipitable water (PW) values
is between 1 and 1.5 inches near the WA/OR coast. The heavier rain
persisted over the S WA coastal mountains last evening is caused  the
Grays River to go above flood stage. Rain has eased overnight but
there should be another round of moderate rain this morning in the
same area, but appears rain rates will be lower than last evening.

It will be a seasonally mild day with high temperatures in the low
60s which is close to daily records for the lowlands. Most of the
rain will be at the coast and north inland zones, with less rain in
the south and east zones.   Another round of rain starts as a cold
front drops in tonight and Thu.  Thanksgiving day will be wet across
the forecast area. For travlers crossing the Cascades on Thu snow
levels will be above pass levels. The front moves east of the area by
Thu evening with residual showers following. Snow level drop down to
the higher Cascade passes Thu night and Fri with snow amounts will
likely be less than an inch or two. For the lowland Fri could be a
dry day especially areas south of Salem.


.LONG TERM...Friday night through Tuesday...The models say the next
system spreads in with more rain Saturday as snow levels rising well
above the Cascade passes.   Snow levels drop back near the passes in
showers behind the front on Sunday. A cool system moves through
Sunday night and Monday with more rain and mountain snow, followed by
decreasing precipitation on Tuesday. Basically the unsettled weather
pattern will continue. Tolleson

&&

.AVIATION...Not much in way of changes today, as weather pattern
will be slow to change. Moist south to southwesterly flow aloft
will maintain plenty of clouds across region, with occasional
light rain. Generally, VFR across region with mix of MVFR and VFR
on the coast. Cold front offshore will slowly push towards today,
with rain gradually increasing later today into the evening.
Front will push increasing MVFR to coast after 22Z, with lower
cigs spreading inland later in the evening.

KPDX AND APPROACHES...VFR conditions through this evening, with
easterly winds 8 to 15 kt. Rain increasing this evening, with
cigs lowering to low VFR, or possibly MVFR by midnight. Rockey.

&&

.MARINE...Rather extensive pressure gradient across the coastal
waters, enough to maintain gusts 25 to 35 kt today, with stronger
winds stay well offshore. Cold front will slowly push across the
coastal waters tonight. This will bring the stronger gusts
closer to shore tonight. Will extend Gale Warning for all of the
coastal waters today through tonight. Southerly winds will be
just below gale force this am, winds will pick up again this
afternoon as the front draws nearer.

Seas generally 12 to 17 ft, but again, the higher seas will be
over the outer waters where the stronger winds reside.

Brief break in the weather for Thu and Fri, with winds generally
15 to 20 kt, and seas relaxing back to near 10 ft. But, another
strong front will bring southerly gales and higher seas again on
Sat into Sun.    Rockey.


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.

WA...None.

PZ...Gale Warning on all coastal waters today and tonight.

     Small Craft Advisory for Rough Columbia River Bar Conditions
  until 10 am today, and again 5 pm to 9 pm today.

&&

$$

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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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