Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 212105
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
204 PM PDT Mon Aug 21 2017

.SYNOPSIS...Onshore flow will produce varying degrees of morning
clouds, afternoon sunshine, with inland temperatures in the 70s and
80s for much of this week. Today and Tuesday will likely be the
warmest days of the work week as a flat upper ridge moves through. A
weak system will bring significant cooling to the forecast area late
Wednesday and Thursday, as well as more clouds and a few light
showers to the forecast area Wednesday night and Thursday. Expect
drying as temperatures warm back to well above seasonal normals
levels next weekend, possibly up into the 90s inland.
&&

.SHORT TERM...Tonight through Thursday...Things settling down after
the eclipse. We posted nice loop of the shadow from GOES-16 imagery
on Facebook and Twitter as it moved through Oregon.

Skies are mostly clear this afternoon with some low clouds and fog
hugging part of the coast. Some light offshore flow is transporting
the smoke from the Whitewater fire and the fires in eastern Lane
county to the southwest into the Willamette Valley south of about
Salem. An upper ridge building into the area will push temps into the
upper 80s to near 90 inland.

The upper ridge shifts east a bit tonight and Tuesday with some
southwest flow aloft developing. This will cause the marine clouds
and fog to spread back onshore along the coast this evening and
tonight, but the inland penetration will be limited Tuesday morning.
The clouds will clear back to near the coastline Tuesday afternoon,
while inland areas will be mostly sunny Tuesday except for local
smoke around. The flow turns onshore inland Tuesday afternoon which
should help decrease the smoke after that. Inland temperatures will
again be very warm Tuesday, in the upper 80s to around 90.

Southwest flow increases Tuesday night and Wednesday as an offshore
system approaches. This will keep the marine layer solid along the
coast, but the models all say there should be a decent push of low
clouds inland Wednesday morning, especially along the Columbia River
into the northern valley areas, and possibly in the southern coastal
gap areas into and around Eugene. The inland clouds should burn off
in the afternoon, but expect the temperatures inland to cool off
closer to 80.

The system that approaches Wednesday moves through our forecast area
Wednesday night and Thursday for increasing clouds, cooler
temperatures, and a few showers. Temperatures will cool off to below
seasonal normals, with 70s common inland. Tolleson

.LONG TERM...Thursday night through Monday...Friday will be a
transition day of drying and warming as westerly flow aloft with
slowly building 500 mb heights spreads in, bringing plenty of
sunshine to the area after areas of morning low clouds. The upper
ridge builds over the weekend and should push inland temperatures up
into the 90s over the weekend and possibly into early next week.
Tolleson
&&

.AVIATION...Satellite and surface observations show VFR conditions
inland and the coast this afternoon, which will persist into the
early evening. Models indicate the marine stratus will move back into
the coastal region in the 03-05z time frame with IFR cigs and vsby
through early Tues morning. The inland penetration of the marine
stratus will be similar to this morning, up the Columbia River to
near Kelso and partially up some coastal river drainages. The stratus
along the coast should retreat back to the coastline mid to late
morning on Tues.

KPDX AND APPROACHES...VFR conditions tonight and Tuesday.
&&

.MARINE...A persistent weather pattern will result in little change
in the marine weather the next few days. High pressure will continue
over the NE Pacific. Models show winds in the 20-25 kt winds near the
surface this afternoon into early evening. Once we get past this
evening, winds should be below small craft strength through the
remainder of the week before northerlies strengthen again by the
weekend as the thermal trough strengthens again. Seas will remain
small but steep through the period. Dominant periods will remain
between 8 and 10 seconds. Rough bar conditions expected on the
Columbia River Bar again Tuesday morning with the very strong ebb. tw
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 11 PM PDT this evening for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Small Craft Advisory for Rough Columbia River Bar from 4 AM to
     8 AM PDT Tuesday.

&&

$$

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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 forecast area.



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