154 
FXUS66 KPQR 030520 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
919 PM PST Wed Jan 2 2019

Aviation section updated.

.SYNOPSIS...A warm front will bring a return of rain and Cascade snow
mostly to the north tonight and Thursday morning before a cold front
supports more widespread rain and Cascade snow Thursday night and
Friday. This front will also produce strong winds along coastal
beaches and headlands Thursday and Thursday night. A low moving south
of Oregon will continue a chance for showers through the weekend,
with snow levels remaining near the Cascade passes.

&&

.SHORT TERM...Tonight through Saturday...The leading warm front
associated with the next low pressure system is now evident on
satellite and NWS radar as it continues to move closer to the Pacific
Northwest. Light rain will move across the region tonight, mostly
north of a Tillamook to Mt. Hood line, with the highest accumulations
remaining north of the Columbia River. There will be a small window
for freezing rain in the Upper Hood River Valley and portions of the
South Washington Cascades late tonight through early Thursday morning
if temperatures hold below freezing until after the moisture arrives,
though it still seems that any accumulation of ice will be minimal,
if any. Overall, moisture will be limited with this front due to most
of the moisture moving north into Western Washington. Snow levels
will begin around the Cascade passes this evening and we could see a
few inches of snow, but snow levels will quickly rise to 6000 feet by
Thursday morning.

A cold front follows close behind and will produce strong gusts for
the coast Thursday night, and more widespread precipitation across
the region. Snow levels will fall to around 4000 feet in the cold air
mass behind the front, and the best moisture behind the front will be
in the South Washington Cascades where 4 to 8 inches of snow can be
expected. Meanwhile, winds will increase on Thursday and Thursday
night along the coast as the cold front approaches. Gusts around 50
or 55 mph will impact the beaches and headlands, but winds are
expected to remain short of high wind criteria and significant
impacts are not expected.

A low pressure system develops over the eastern Pacific and moves
north off the California coast. This will allow some continued
showers in the flow around the low early in the weekend, though there
does remain some uncertainty in where this low will track.  

.LONG TERM...Saturday night through Wednesday...The 12z GFS and 12z 
ECWMF look to be in overall agreement through the extended period. 
Saturday night has our area sandwiched between a low that has made 
landfall around Vancouver Island, and a offshore California low. 
This set up will keep temperatures above normal, as well as keep 
precipitation chances up in the area. Sunday has the California low 
making landfall around the Oregon/California border. This low is 
tied to an atmospheric river pattern, which will keep temperatures 
on the warmer side, in addition to keeping precipitation chances on 
the higher side. Snow levels over the weekend are still going to be 
at or around pass level (~4000 ft), which will still enable snow 
fall and accumulation at higher elevations during this time period. 
As Monday approaches we see a low once again pointed towards 
Vancouver Island, with the associated front keeping the area well 
saturated through the early part of next week. /42

&&

.AVIATION...Rain moves onto the coast 09Z-11Z with MVFR CIG.  
This rain will spread gradually east overnight, impacting all the 
terminals except EUG by Thursday morning, but conditions are more 
likely to stay VFR inland. The back side of this warm front moves 
through around 18Z inland, meaning a break in the rain and a return 
to predominantly VFR CIGs for anywhere that drops to MVFR with the 
front. With this break, we will see southerly winds start to 
increase, with gusts up to 20 to 25 kt inland, and gusts up to 30 to 
35 kt at coastal terminals.

KPDX AND APPROACHES...Should see VFR conditions next 24 hours. Small 
chance of high MVFR with rain between 12Z and 18Z. Southerly winds 
increase after 18Z, gusting as high as 25 kt. Bowen
-McCoy

&&

.MARINE...Winds are ramping up over the waters this afternoon,
with gusts to 27 kt already being observed at buoy 29, and
approaching 20 kt at buoy 50. As the warm front continues to lift
north, will see winds ramp up across our northern waters, with
gales for the zones north of Cascade Head starting around 8 PM
this evening. Farther south will probably not see gales until the
cold front gets closer around 3 AM Thursday. Expect winds to peak
Thursday afternoon and evening just ahead of the cold front, 
when we will see gusts up to 45 kt, and perhaps a few occasional 
gusts up near 50 kt. Winds will drop off fairly quickly behind
the front and turn southwesterly, though there will be a second
round of lower-end gales Friday morning where a trough following
the front brushes our northern zones. 

Seas are starting to build, already up around 8 to 9 feet. Seas
will continue to build, rising above 10 feet over the next few
hours, and peaking Friday morning in the low 20s. Surf heights
are starting to approach High Surf Advisory criteria, so we may
even need a High Surf Advisory for late Thursday night and Friday
morning with the large seas, as the wind wave transitions to more
of a westerly swell. 

Winds finally drop below 20 kt Friday afternoon, with a break in
the weather pattern as the next system stays well to our south.
Seas drop below 10 feet late Saturday afternoon or Saturday
evening. The next system to impact our waters could bring another
round of gales Sunday night into early Monday. -McCoy

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.

WA...None.

PZ...Small Craft Advisory for winds until 8 PM PST this evening for 
     Coastal Waters from Cape Shoalwater WA to Cascade Head OR 
     out 60 NM.

     Gale Warning from 8 PM this evening to 6 AM PST Friday for 
     Coastal Waters from Cape Shoalwater WA to Cascade Head OR 
     out 60 NM.

     Small Craft Advisory for winds until 3 AM PST Thursday for 
     Coastal Waters from Cascade Head OR to Florence OR out 60 
     NM.

     Gale Warning from 3 AM Thursday to 4 AM PST Friday for Coastal 
     Waters from Cascade Head OR to Florence OR out 60 NM.

     Small Craft Advisory for Rough Columbia River Bar from 10 PM 
     this evening to 6 AM PST Friday.

&&

$$

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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.