Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 202150

Area Forecast Discussion
National Weather Service Portland OR
250 PM PDT Wed Mar 20 2019

.SYNOPSIS...Low pressure moving into California will continue to
spread clouds across Northwest Oregon and Southwest Washington this
afternoon, with a slight chance of showers over the southern portion
of the forecast area. More seasonable temperatures will spread across
the forecast area Thursday, with a couple of lingering showers still
possible. Widespread rain is expected to develop Friday as a
better-organized frontal system moves onshore, with post-frontal
showers lingering into the weekend. The active weather pattern looks
to continue into next week.


.SHORT TERM...Tonight through Saturday...Satellite imagery continues
to show a negatively-tilted upper level trough slowly moving into
California this afternoon, spreading increasing mid and high clouds
over portions of the forecast area. Unfortunately, these clouds were
slow to arrive this morning so expect another round of record or near
record high temps this afternoon under weakening offshore flow.

We will continue to see a non-zero chance of showers across portions
of the forecast area this evening and tonight as wraparound moisture
from the upper level trough moving into California moves across the
forecast area, but given how dry our air mass is this afternoon don`t
think we will see a lot of moisture hit the ground. Expect much more
seasonable temps tonight and Thursday as onshore flow starts to
increase ahead of an approaching frontal system.

Guidance then shows a modest frontal system moving across the Pac NW
on Friday which should bring another round of widespread rain to the
region. Models remain in general agreement that rain will spread
onshore sometime Friday morning, then across the rest of the forecast
area Friday afternoon and evening, with conditions becoming more
showery by Friday night. Post-frontal showers look to continue into
Saturday as a weakly unstable air mass lingers over the region.

.LONG TERM...Saturday night through Wednesday...The effects of the
low that passes over the forecast area Friday will dissipate through
Saturday night. Sunday will be dry based on a short-wave ridge ahead
of the next large system. Sunday night shows a slow moving low off
the Oregon coast that will pass slightly south of the forecast area.
This system will bring precipitation Monday afternoon through
Thursday. The coldest temperatures during the day look to be on
Monday due to the cold front ahead of this system. Snow levels will
stay above 3000ft so only the Cascades will see snow as this system
passes. --BPhillips


.AVIATION...Weak front approaching from the southwest will push
variable mid and high clouds across region today through tonight,
but generally stays dry. Expect patchy IFR to low MVFR
conditions to move onto the central coast this afternoon and then
slowly spread north later this evening. Reduced flight
conditions look to continue along the coast through Thu morning
as onshore flow increases. Will also see an increasing chance of
MVFR cigs in the interior Thu morning.

KPDX AND APPROACHES...VFR with variable mid and high clouds today
into tonight. Offshore winds will weaken later today, with winds
becoming light south to southeast this evening. Expect an increasing
chance of MVFR cigs Thu morning. /64/Rockey


.MARINE...A very small scale surface low will bring frequent
gusts 20-25 kt this evening mainly to the inner central waters
and the northern waters inside of 25 nm. Seas may briefly touch
10 ft but feel they will predominantly stay 6-9 ft this evening.

Next front will push into the region later Fri. Likely to see
southerly winds 15 to 25 kt at that time. While small potential
of gusts up to 35 kt, think orientation of front being more
northwest to southeast does not favor such winds. So, will trend
to keep winds under 30 kt. But, will see building swell with the
front, with seas building above 10 ft Fri afternoon, and holding
at 12 to 14 ft Fri night through Sat night. Seas subside on
Sunday, but still near 10 ft. /JBonk/Rockey


PZ...Small Craft Advisory for winds until 11 PM PDT this evening for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     10 NM.Waters from Cape Shoalwater WA to Cascade Head OR
     from 10 to 60 NM.

     Small Craft Advisory for Rough Columbia River Bar until 8 PM
     PDT this evening.

     Small Craft Advisory for Rough Columbia River Bar from 5 AM to
     9 AM PDT Thursday.



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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. is the U.S. government's official web portal to all federal, state and local government web resources and services.