Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 221014
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
314 AM PDT Sat Sep 22 2018

.SYNOPSIS...Mild and showery today. Showers limited to mountains
Sunday morning. Dry and warmer weather returns next week.

&&

.SHORT TERM...Today through Monday...Front moved through last evening
dropping a modest amount of rain. As of 2 am coastal areas and north
Cascades had 0.15-0.20" while the north interior under a 0.10".  More
showers are on the way today as an upper trough offshore approaches
the area.  Model soundings show a fairly unstable air mass this
afternoon so some showers could produce brief moderate to heavy
rainfall. Model soundings show a cap just around the freezing level
so do not expect there will be enough ice will be present in the
showers to generate lightning.Most of the showers will be north of
about Salem and in the mountains.  The upper trough moves through
tonight with showers becoming more confined to the mountains. During
the day on Sunday, drier north to northwesterly flow will overspread
the region and result in decreasing clouds, but a rather pleasant
fall-like day. Shortwave ridging will begin to build eastward over
the Pacific Northwest Sunday night and Monday, which should result in
interior locations warming into the 70s. Breezy northerly winds may
develop along the coast and in the Willamette Valley as thermal low
pressure begins to strengthen over southwestern Oregon. /mh /Neuman


.LONG TERM...Monday night through Friday...The long term part of
the forecast can be characterized as a brief return to summer or
first real taste of Indian Summer. The operational ECMWF, GFS and
CMC in good agreement through the period. In addition, the WPC
forecast is close to the GFS and its ensembles. A 590 dm 500 mb high
pressure center will be centered out near 45N 130-135W Tue and Wed.
North to Northeast 700 mb flow and a Northeast to East 850 mb wind
regime will result in a dry air mass over the area. Model forecast
850 mb temps Tue and Wed are 15 to 18C. These values would typically
produce mid to upper 80s for the interior valleys. However, with
shorter days and stronger night and morning inversions, full mixing
will likely not be realized. In any event, inland valleys should
still reach the lower 80s. The offshore low-level flow will aid in
warming, especially along the coast. A thermally-induced surface
trough is expected to reside near the coast Monday night then drift
to the interior valleys Tue. The offshore gradient Tue and Wed does
not appear to be all that impressive, but would still expect locally
breezy to windy conditions.

By Thu the CMC and GFS show the forecast area within a col area. The
500 mb high center closes off out near 140W with a closed low
directly to the south. Thus, would expect above-normal daytime
temperatures to continue Thu, but with weaker offshore low-level
flow. 12Z operational models then start to retrograde the strong
north 500 mb flow forecast to be present over the Northern Rockies.
This would bring cooler air through Eastern Washington and Northeast
Oregon. Some of this would slip through the Central Columbia River
Gorge and the Upper Hood River Valley. Bottom line: No precipitation
expected through the period and above-normal daytime temperatures.
Weishaar


&&


.AVIATION...Southwesterly flow aloft will turn more westerly
later this am. Generally, MVFR and low VFR with cigs 2500 to 3500
ft across region, with pockets of IFR CIGS along the coast. Will
continue to see spotty showers early this am. But, as cooler air
offshore spreads inland, expect scattered showers to increase
along the coast early this am, and spread inland through 19Z.
Generally, VFR after 18z, with brief MVFR under heavier showers.

KPDX AND APPROACHES...Mostly VFR this am with occasional MVFR
CIGS, with few showers around the ops area. Not much change
today, though will see showers increasing after 16Z as air mass
becomes bit more unstable.      Rockey.

&&

.MARINE...Cold front has pushed onshore this am, with gusty south
to southwest winds on the waters. Winds will gradually ease
later this am into the afternoon. Seas still rather steep and
wind chop dominated at 6 to 8 ft. But seas will subside a bit
later today as well.

Rather benign weather for tonight into Sun. But, thermal low
pres will build along the south Oregon coast early next week,
setting up tighter pres gradients. This will result in gusty
northerly winds on the waters, with gusts 20 to 30 kt at times
later Mon, along with more choppy wind driven seas, mainly to
south of Newport. This pattern will hold into most of next week.
Rockey


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until noon PDT today for Coastal
     Waters from Cape Shoalwater WA to Cascade Head OR out 60
     NM.

     Small Craft Advisory for hazardous seas until 10 PM PDT this
     evening for Coastal Waters from Cape Shoalwater WA to
     Cascade Head OR out 60 NM.

     Small Craft Advisory for winds until 5 AM PDT early this
     morning for Waters from Cascade Head to Florence OR from
     10 to 60 NM.

     Small Craft Advisory for Rough Columbia River Bar until 6 AM
     PDT early this morning.

     Small Craft Advisory for Rough Columbia River Bar from 2 PM
     this afternoon to 6 PM PDT this evening.

&&

$$

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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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