Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 240940
Area Forecast Discussion
National Weather Service Portland OR
240 AM PDT Sun Jul 24 2016
.SYNOPSIS...A weak upper trough will develop near the coast today
with weak westerly flow aloft over the Pacific Northwest through
Monday and Tuesday, bringing slight cooling and increasing low
clouds inland Monday and Tuesday mornings as compared to this
morning, along with some patchy morning drizzle along the coast.
After Tuesday, a stronger upper level ridge will build for the
second half of the week and bring inland highs well into the 90s
Thursday and Friday.
.SHORT TERM...(Today through Tuesday)...Despite model low level RH
forecasts, low clouds have been slow to develop early this morning.
Still expect some to develop but have eased back on the coverage this
morning. Any that do form will not last long and today will have more
sunshine than recent days. This will help push temperatures most
areas a bit above normal today, with mid 80s common inland this
The models continue to show a very weak baggy upper trough developing
today in a light westerly flow aloft that will persist into Monday
and Tuesday. The models indicate that this weak upper trough will
likely increase the coverage of low clouds the next two mornings,
with some surge inland both along the Columbia River and through the
southern coastal gap toward Eugene, with the two flows of low clouds
trying to converge on the central Willamette Valley. The clouds
should clear back to the coast in the afternoons each day. The
models also show some coastal drizzle Monday and Tuesday mornings as
The air mass aloft is rather dry and combined with the light westerly
flow suggests that any threat of thunder is very low and will
continue to be omitted from the forecast. Tolleson
.LONG TERM...(Tuesday night through Saturday)...No changes. Previous
discussion follows. A weak upper level ridge will dominate most of
the long term forecast. This will bring the familiar pattern of
morning clouds and afternoon sun, with temps in the interior rising
into the 90s late next week. Some relief is possible late next week
as models continue to show an increase in onshore flow.
It is worth noting that today`s 12Z GFS is showing some monsoonal
moisture streaming north on Saturday. If this pans out we could see
some thunderstorms develop in the Cascades, but confidence is low so
will leave it out of the forecast for now. /64
.AVIATION...Clouds have yet to form across the local area but still
think the coast will see MVFR cigs develop within the next few hours.
Less confident about any clouds inland and am leaning toward cigs
remaining near the coast, possibly making it to KKLS but not any
further. Overall the marine layer should be less deep so it will
dissipate sooner today, with VFR all areas by late morning. Coastal
winds increasing starting late morning as well. Gusts to 25 kt likely
along the coastline during the afternoon through early evening hours.
KPDX AND APPROACHES...Leaning more towards VFR through the forecast
period. If any MVFR cigs do make it to the terminal, it will be late,
closer to 15Z, and only last a couple of hours. Bowen
.MARINE...Main marine issue will be winds, which have decreased below
20 kt tonight but will pickup again late Sunday morning. It looks
like each day this week will be fairly similar with winds picking up
in the afternoon and evening hours and dropping off some overnight.
Upper ridge strengthens Tuesday, which allows for a stronger surface
gradient, which may allow gusts as high as about 30 kt during the
afternoon and evening hours.
Overall wave heights will be 4 to 7 ft through most of the workweek
with possible higher seas toward the end of the week and into next
weekend. Highest waves during the week will occur over the waters off
the Central OR coast where winds will also be strongest. Seas will be
dominated by fresh swell much of the week, so, as is typical for
summer, they will be a bit steep. Bowen
PZ...Small Craft Advisory for winds from 2 PM this afternoon to
midnight PDT tonight for Coastal Waters from Cape
Shoalwater WA to Cascade Head OR out 60 nm.
Small Craft Advisory for winds from noon today to 3 AM PDT
Monday 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. The area is commonly
referred to as the forecast area.