Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 102151

Area Forecast Discussion
National Weather Service Portland OR
248 PM PDT Mon May 10 2021

.SYNOPSIS...Upper level high pressure will result in another multi-
day stretch of dry weather and above average temperatures this
upcoming week. The next chances for rain hold off until the weekend
and do not really start to climb until late next Sunday/Monday.


.SHORT TERM...Tonight through Thursday...Water vapor imagery
confirms models have a good handle on the current upper level ridge
over the region. This low amplitude ridge, now centered at 135-140W,
will slowly drift eastward this week to bring temperatures warming
into the mid to upper 70s. Temps peak on Wednesday before slowly
cooling off toward the weekend. Surface thermal low pressure over
California and another stronger low over the Great Basin will bring
a very typical diurnal summertime pattern to the region. Expect
areas of morning clouds followed by afternoon sun. Seabreeze winds
will generally pick up by early afternoon and become gusty through
the evening, especially near gaps in the Coast Range. This natural
air conditioner effect will also help moderate daytime temperatures
and bring pleasantly cool nights. Unfortunately, no precipitation is
on tap, although the daily onshore flow regime will keep dew points
from becoming overly low and humidity from getting too dry. /JBonk

.LONG TERM...Thursday night through Monday...Unfortunately not much
precipitation to look forward to for the rest of this week and
weekend. Models and related ensembles continue to keep our forecast
area dry on Thursday through Saturday by digging a trough well
offshore and then developing into a cutoff low off the southern
California coast. It then moves east to leave the PacNW under a
fairly dry split flow aloft. The only PoPs in our forecast now
Saturday to account for some uncertainty with how far south the
closed low actually develops and potential weak instability.

Models then move a broad/low amplitude trough south from the Gulf of
Alaska Sunday through early next week. There is enough uncertainty
that the full envelope of model data from the NBM keeps some slight
chance PoPs for Sunday and Monday. Given trends over the last few
weeks, am finding it hard to get excited until we see these modeled
troughs make an appearance in the front half of the forecast package
instead of gradually disappearing as time draws closer. /JBonk


.AVIATION...High pressure aloft continues to build into the
region. At the surface, onshore flow will continue for the next
few days, this will bring MVFR stratus to the coast overnight
into the early morning hours, but may persist a bit longer for
areas KTMK northward. MVFR stratus should develop along the lower
Columbia River to near KTTD for a few hours Tue morning. Expect
cloud cover inland to be less than today. Winds this evening will
be gusty particularly along the central coast. Winds then ease
tonight then pickup again Tue afternoon.

For detailed regional Pac NW aviation weather information, go online

KPDX AND APPROACHES...VFR conditions prevailing through at least
12Z Tue, then a decent chance for MVFR cigs for a few hours Tue
morning especially for towards KTTD. /mh


.MARINE...High pressure will be the dominant feature over the
coastal waters through at least Friday. At the same time, a
surface thermal trough will persist from northwest CA to the
south OR coast for a prolonged period of northerly winds over
the coastal waters. Winds will be strongest during the afternoon
and evening hours. Have extended the small craft advisory for PZZ
255 & 275 through Tue night, but may see marginal small craft
advisory wind extend into the north. In addition to the winds,
seas will be fairly choppy of the central coastal waters next
couple of days.


PZ...Small Craft Advisory until 11 PM PDT this evening for coastal
     waters from Cape Shoalwater WA to Cascade Head OR out 60

     Small Craft Advisory until 3 AM PDT Wednesday for coastal
     waters from Cascade Head OR to Florence OR out 60 NM.



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