High Surf in Washington, November 25, 2020

Area Forecast Discussion
National Weather Service Portland OR
314 AM PST Wed Nov 25 2020

.SYNOPSIS...Showers are forming in the post cold frontal environment
as snow levels continue to drop. Precipitation expected through at
least Wednesday afternoon with the potential for isolated showers in
the evening. High pressure builds back in on Thursday through Friday.
Chance for a bit more active weather starting Saturday through early
next week.

&&

.SHORT TERM...Today through Friday night...The cold front that
brought an initial stronger shot of precipitation to the area has
since moved inland leaving behind a move convective environment it
it's wake. While the frontal precipitation and breezy winds have
passed, showers remain bringing periods of more intense rain and snow
showers to the Cascades. Snow levels are dropping as cooler air pools
in behind the cold front. Snow levels have lowered down to around
3500 ft with temperatures at 5000 ft around -3 degrees celsius. With
the lowered snow levels and persisting rain, can expect another
several inches of snow, especially above 5000 ft. As previously
mentioned, there is some lingering convection behind the front which
may produce some isolated weak thunderstorms along the coast line.

Overnight into Thursday, the remaining showers will dissipate as high
pressure over the Pacific builds. This ridge aloft stretches north
across British Columbia, while near the surface it is slightly
flatter. Because of the less amplified surface feature, winds will
generally remain fairly week and offshore. Expecting clearing skies
and dry conditions Thursday through Friday. With the clearing skies
and winds becoming light in the evenings, there is a strong chance
for fog development in many locations below 1000 ft. Fog likely will
become dense at times in more prone areas around the southern
Willamette Valley and backing up to the Coast Range foothills.

Do note that in addition to the Winter Weather Advisory currently in
place, there are high surf conditions present through Thursday. For
more information on sea states please refer to the marine discussion.
  -Muessle

.LONG TERM...Saturday through Tuesday night...In the long term is
where a bit of uncertainty lies. Many operational models are showing
a second front moving over the region late Friday night into
Saturday. This front will bring another round of precipitation to the
area starting Saturday morning. The challenge with this system is
both in the timing and track. Over the last 24 hours, the system has
shifted a bit further south and is weakening as it approaches the
area. Because of this, decided to trend towards a more moderate
solution with generally lower PoPs.

Another period of high pressure forms Saturday night through Sunday
which will likely again keep things dry and fairly settled...though
it will be short lived. On Monday however, conditions change. As it
stands, a long wave trough with a closed low at the base will advect
over northern California Monday morning, increasing precipitation.
Many long range models are suggesting at a similar solution but with
different tracks and outcomes. Ultimately time will tell how that
system will pan out but there definitely is a potential for more
active weather early next week.   -Muessle

&&

.AVIATION...Cool, westerly flow aloft will maintain unstable air
mass, with plenty of showers especially along the coast and over
the higher terrain. With this, will maintain a mix of VFR and
MVFR, with the lower conditions around showers. Also, with larger
breaks in the cloud cover and cool moist air mass, do have
pockets of fog through 16Z, mainly inland. A weak system over
western Washington will push inland today, with more clouds and
increasing showers, with more MVFR than VFR for sw Washington
southward to PDX/VUO area. Heavier showers will produce small
hail as freezing level holds near 3000 feet. Can not rule out an
isolated thunderstorm along the coast as well today.

Showers decreasing tonight, but still plenty of onshore flow.
This will maintain lot of clouds through 08Z, mostly VFR.

For detailed regional Pac NW weather information, go online to:
http://weather.gov/zse

KPDX AND APPROACHES...Mix of VFR and MVFR, along with occasional
showers today. Though, likely to see more MVFR than VFR this am,
especially between 12Z and 18Z. Stronger showers will produce
small hail, mainly after 18Z. Showers decreasing after 03Z, but
mix of MVFR and mostly VFR CIGS will continue.		/Rockey

&&

.MARINE...Cool unstable air mass over the coastal waters will
maintain plenty of showers today into tonight. But, pressure
gradients are not all that strong, so will see westerly winds
running 10 to 20 kt. With the showers, would expect some gusts 20
to 25 kt in spots.

West swell of 19 to 22 ft are still rolling through the coastal
waters today. These will gradually subside tonight into early
Thu, with seas dropping back to 10 to 12 ft during the day Thu,
then back under 10 ft Thu night.

High pressure will sit across the region for Thu and Fri, with
lighter winds, with seas mostly 8 to 11 ft. Another weak front
will push across the region Fri night. High pressure build over
the inland Pac NW this weekend, and holds through Wed.	/Rockey

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory until 4 AM PST Thursday for Central Oregon
     Coast-North Oregon Coast.

     Winter Weather Advisory until 7 PM PST this evening for
     Cascades in Lane County-Northern Oregon Cascades.

WA...High Surf Advisory until 4 AM PST Thursday for South Washington
     Coast.

     Winter Weather Advisory until 7 PM PST this evening for South
     Washington Cascades.

PZ...Small Craft Advisory until 10 AM Thu for Columbia River Bar.

     Small Craft Advisory until 6 PM Thu on all Coastal Waters
       from Cape Shoalwater to Florence.

&&

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