River Flood Warning 3, NWS Portland, OR

Area Forecast Discussion
National Weather Service Portland Oregon
931 AM PDT Mon Oct 17 2016

.SYNOPSIS...Westerly flow aloft will keep a seasonably cool
showery weather pattern through mid week. A weak ridge of high
pressure aloft moving across during the latter half of the week may
bring a brief respite from the showers late in the week or over the
weekend.

&&

.SHORT TERM...(Monday through Wednesday)...A series of
shortwaves extending west of the Pacnw is depicted well on water
vapor imagery.	the first one is now moving across over the CWA
producing showers and a few thunderstorms over the coastal waters
over the south Oregon coast. The leading edge of the next shortwave
is now near 129W and is projected to move across the CWA this
afternoon for an increase in shower activity.  Thunderstorm chances
is expected to extend from the coastal areas inland for the afternoon
and early evening, but a low threat is expected to continue overnight
into Tue over the coastal areas. Model soundings show weak shear and
potential for deep vertical development this afternoon so some
showers/thunderstorms may be quite active and produce brief heavy
rain.

Tue afternoon into Tue night models agree on weak ridging
aloft tending to stabilize the atmosphere as well as weakening the
moist onshore flow, so expect to see showers tapering off then. With
the flat ridge Wed, it is difficult to rule out a chance for some
rain or showers sneaking back in as models to varying degrees
suggest some weak isentropic lift reaching the coast, while ec
suggests some showers over the Oregon Cascades.

No significant hydro issues expected today but recent moderate to
heavy rain over the higher terrain in Pacific & Wahkiakum counties
have bumped up the Grays River to near bankfull.  Radar shows the
showers will be easing soon so do not expect too much more rise in
the river.

.LONG TERM...(Wednesday night through Sunday). No changes. Previous
discussion follows. A frontal boundary will move across the area
late Wednesday into Friday bringing more showers, but weaken as it
moves through. Models diverge a bit on the weekend, but Saturday
might be fairly dry with rain returning Sunday. tw

&&

.AVIATION...A moist and unstable air mass will help to maintain
scattered showers over the forecast area today and tonight, with
isolated thunderstorms possible west of the Cascades. Expect
predominately VFR conditions, with brief periods of MVFR cigs
and/or vsbys possible under heavier showers.

KPDX AND APPROACHES...Primarily VFR under scattered showers. Brief
periods of MVFR cigs and/or vsbys possible under heavier showers.
/64

&&

.MARINE...Low pres over the waters will continue to shift inland
today, with winds subsiding below 20 kt later this morning. Seas
are currently around 12 to 14 ft this morning, but are expected to
gradually subside to around 10 ft by this evening and hover in
this range through Tue, then maybe drop under 10 ft Tue night.

After a brief break Tue, another frontal system will arrive Wed
and Thu. First part will be a warm front that will lift across the
region on Wed, with gusty south to southeast winds generally 25 to
30 kt. Cold front will arrive on Thu, then winds ease again. Seas
look like they will rise to just above 10 ft. /64/Bowen

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Coastal Flood Advisory from 1 PM to 4 PM PDT this afternoon for
     South Washington Coast.

PZ...Small Craft Advisory for winds until 11 AM PDT this morning for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Small Craft Advisory for hazardous seas until 5 AM PDT
     Wednesday for Coastal Waters from Cape Shoalwater WA to
     Florence OR out 60 nm.

     Small Craft Advisory for Rough Columbia River Bar until 9 PM
     PDT this evening...and again from 3 AM to 9 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. The area is
commonly referred to as the forecast area.