Area Forecast Discussion
Issued by NWS Portland, OR

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924
FXUS66 KPQR 161644
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
944 AM PDT Wed Aug 16 2017

.SYNOPSIS...Northwest flow aloft will maintain onshore low level flow
across the region through the week that will keep temperatures near
seasonal normals. High pressure aloft strengthens over the weekend
for continuing dry weather. The region will remain in between two
upper level low pressure systems, one dropping south from the Gulf of
Alaska and a cut-off low off California. This will maintain
seasonable temperatures with typical morning clouds and afternoon
sunshine.

&&

.SHORT TERM...Today through Friday...This morning we are seeing some
marine stratus on the SW Washington Coast and the far N Oregon Coast
and in the Columbia River inlet west of Westport. Otherwise, the rest
of our area is clear and sunny this morning. Expect weather today
will be fairly similar to yesterday as the persistent pattern of
northwesterly flow continues with a near stationary ridge over the
Central Pacific. A weak trough riding along the top of the ridge will
rotate through tonight and the high pressure offshore will bring a
deeper marine layer into our area. This will create more stratus
along the Coast tonight and bring more stratus inland Thursday
morning. Temperatures Thursday afternoon will be a couple degrees
cooler than today across the area as a result.

On Friday there should be less low cloud coverage inland than there
was on Thursday, with the best chance in the north along the Columbia
River. There is a short wave moving through that will be increasing
the westerly onshore flow and the westerly flow aloft through the
day, keeping temperatures in check despite a decent amount of
sunshine, and setting the stage for increased low clouds coverage
Saturday morning much like on thursday morning. -McCoy

.LONG TERM...No Changes. Previous discussion follows...
Friday night through Tuesday...Models remain in fairly good agreement
for the weekend. An upper level trough approaches the region, and an
upper low cuts off from the flow off of northern California as it
rounds the broad high pressure over the eastern Pacific with the
upper ridge axis centered near 140W. This will leave the region under
diffluent flow aloft and weak onshore flow at low levels after
increased low clouds coverage Saturday morning. Continue to maintain
a dry forecast for Sunday through Tuesday with some overnight/morning
cloud cover. Embedded shortwave impulses ahead of the primary upper
trough may either increase cloud coverage, depending on their timing
and at this lead time confidence in the precise cloud cover remains
low to moderate. That said, there does seem a notable trend towards
at least somewhat favorable eclipse viewing conditions. The key area
of lower confidence at this point is just how thick and widespread
any morning clouds will be. Confidence will hopefully increase in the
next several days, and with all eyes focused on Monday`s eclipse,
continue to monitor the latest forecast with the expectation that
some changes will be made as the forecast is refined over the coming
days.    Cullen

&&

.AVIATION...Marine stratus will bring a period of IFR to low-end
MVFR cigs to portions of the coast north of KTMK. The stratus
will likely linger along the north coast today, but should lift
to VFR this afternoon. Based on recent trends, don`t think the
stratus will bring reduced cigs to the central coast. Expect
conditions similar to yesterday.

The interior will remain predominately VFR today and tonight.
Late tonight expect MVFR stratus to increase along the coast and
north interior.

KPDX AND APPROACHES...VFR the next 24 hours. Areas of stratus
possible after 12Z Thursday. /42

&&

.MARINE...High pres will remain centered over the coastal waters
through the weekend, with thermal low pres over northern CA and
south west OR. This will maintain the summer-time northerlies,
with breezy winds developing during the afternoon/evening hours
over the next several days, especially south of Newport. A small
craft advisory for winds is in effect this afternoon/evening for
the central OR waters. Expect additional small craft advisory
for winds through the weekend.

Seas will generally be around 5 to 7 ft through the period, but
may build to around 8 ft at times as the winds increase. Seas may
also become steep at times during the afternoon/evening hours.
/42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 3 PM this afternoon to
     10 PM PDT this evening for Coastal Waters from Cascade
     Head OR to Florence OR out 60 nm.

&&

$$

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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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