Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 171019
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
314 AM PDT Thu Aug 17 2017

.SYNOPSIS...Persistent surface high pressure over the NE Pacific
combined with low pressure east of the Cascades will maintain onshore
winds the next several days. Slight variations of the upper level
pressure pattern will result in slight variations in how expansive
nighttime/morning clouds will be through early next week. The clouds
should clear in the afternoons with temperatures remaining near the
seasonal normals. An upper level ridge is expected early next week
for less clouds and slightly warmer temperatures.

&&

.SHORT TERM...Today through Saturday...Stratus solidly on the coast
and pushing through lower gaps in the coastal terrain. The lower
level pressure pattern is more favorable for clouds to fill in over
SW WA into the interior lowlands.  Clouds have made it to the Salem
area and should also reach Eugene area this morning. A passing weak
upper level shortwave trough north of the area has deepened the
marine layer enough for some light drizzle or rain at the north
coastal zones early this morning.   Lowlevel winds become more
northerly as the day progress which will help clearing the clouds
later this morning inland and in the early afternoon at the coast.
Temperatures will again be near seasonal normals.

There will be little change in the weather Thursday night and Friday
as another upper level trough passes by to the north and low-level
onshore winds persist. The marine layer should deepen late Friday
night and early Saturday morning as an upper level trough develops
over NW Oregon for a better chance for more widespread clouds
Saturday morning.  Therefore the temperatures Saturday afternoon will
be slightly cooler. /mh ~TJ

.LONG TERM...No Changes. Previous discussion follows...Saturday night
through Wednesday. Overall, rather benign pattern with varying
degrees of onshore flow for the weekend. Weak system will pass to
over region on Saturday, but seems system is splitting. This will
keep local mostly dry, with threat of any showers staying well north
over British Columbia. But this system will allow for increased
onshore flow, with some spotty drizzle along the the coast. Mainly,
expect more in way of clouds around region for Sat, and again later
Sat night into Sun.

Now, for the big question...what about Monday?At this time, looks
like will slip back into the pattern we have had the past few days.
This will keep threat of late night and morning clouds along the
coast, mainly to north of Newport. But, interior looks to remain
mostly clear on Mon through can not rule a few clouds along and to
north of the Columbia River prior to 10 am. Temperatures staying
near seasonable.

But changes appear in store for the region for Tue and beyond. Upper
low off Calif coast will start drifting northward, bringing a return
to southerly flow over the region. This will allow for increasing
threat of afternoon/evening thunderstorms over the Oregon Cascades.
Temperatures still near seasonable levels.   Rockey.

&&

.AVIATION...Marine stratus will continue to bring predominately
MVFR conditions to the coast this morning, with brief and local
IFR fog possible. Guidance continues to suggest that the coastal
stratus will brief scatter out this afternoon for a few hours of
VFR, but would not be surprised to see reduced flight conditions
continue into tonight.

MVFR stratus will continue to fill into the interior this morning
and bring reduced flight conditions to most interior TAF sites.
Based on the current satellite imagery think KEUG may remain VFR,
but could see patchy MVFR stratus around the area. Expect stratus
in the interior to scatter out later this morning, with VFR cigs
possible after 18Z. MVFR stratus likely returns to the northern
interior late tonight.

KPDX AND APPROACHES...MVFR stratus will linger over the terminal
through late this morning. Stratus is expected to scatter out by
18Z, giving way to VFR conditions this afternoon. MVFR stratus
likely returns late tonight.

&&

.MARINE...High pres will remain over the coastal waters through
early next week, with thermal low pres over northwest California
and southwest Oregon. This will keep our summer-time northerlies
in place, with breezy winds developing in the afternoon/evening
hours for the next several days, especially south of Newport. A
SCA for winds remains in effect from this afternoon through early
Friday, with additional advisories likely this 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.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 1 PM this afternoon to
     5 AM PDT Friday 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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