High Surf in Oregon, January 4 to 6, 2023

Area Forecast Discussion
National Weather Service Medford OR
234 PM PST Wed Jan 4 2023

.DISCUSSION...The area is in the midst of a potent winter storm
that will continue into Thursday. Although snow level continue to
climb above most of the major passes along I-5, and soon over the
passes over the Cascades with the air temperature at Lake of the
Woods at 35 degrees at this time, colder temperatures remain in
the Mount Shasta region. This is most likely due to the higher
precipitation rates combining with cold air pooling, but more due
to the cooling with the higher precipitation rates. This is
resulting in continued snow along 89 and Snowman Summit and Black
Butte Summit in spite of the higher snow levels outside of this
area. With this in mind am keeping with the current ending of the
lower level advisory as snow levels rise very early this evening
with just the warning above 4500 ft elevation remaining into late
evening, then further rising above 5500 feet and above elevations
where warnings are issued.

Otherwise the main event with this system is winds, which are
affecting almost all of the region. Winds are starting out with a
southeast component, resulting in lighter winds at the coast.
However, winds over the rest of the region have been strong, with
a gust to almost 100 mph at Squaw Peak RAWS today. winds will
continue to increase later this afternoon with southerly 700 MB
winds increasing to around 80 kt shortly. Where the winds have
been surfacing over the west side, other than in the Shasta Valley
and southern Rogue valley near Ashland, has been somewhat random
and resulted in numerous power outages west of the Cascades. Of
course much of these power outages are related to trees falling
onto power lines, and trees are much more numerous west of the
Cascades. Although the pressure gradient between Redding and
Medford loosens overnight, the BL to 850 MB winds become more
southerly and aligned with the valley, and though winds should
subside a little bit, they are expected to remain strong into
Thursday. The very strong ridge winds finally taper off Thursday
from west to east, dropping to below advisory over all of the
region by mid to late afternoon. Sven

.Long Term...Friday 1/6 through Wednesday 1/11...

The wet and windy pattern will continue throughout the long term
forecast period. The pattern that has set up over the Pacific
remains relatively consistent, with a large low spinning just
southwest of the Aleutians acting as a "cannon," firing system after
system across the Pacific and into the West Coast.

How each system affects southern Oregon and northern California will
depend on the track and intensity of each individual upper level
trough and associated surface low. There is a great deal of spread
across the ensemble suites, so it is very difficult, even
impossible, to nail down the details at this time. That being said,
we can expect the wet and windy pattern to continue, with frontal
systems passing every one to two days.

The first of these systems arrives Friday, with a weaker surface low
passing to  our northwest. A second system follows on Saturday, and
previous model runs suggested this would be a strong event, similar
to the one occurring today and tomorrow. In the latest runs, the
system has weekend and tracked farther south, impacting northern and
central California much more than southern Oregon. Additional
systems are then lined up through Wednesday, although their strength
and track change significantly across model suites and model runs.
Throughout this time, snow levels should remain around or above 4000
feet, so some travel impacts are likely for the higher mountain
passes, but not elsewhere.

There is little reason to believe that wet conditions will end soon,
as the far long range models continue this active pattern through
next week and into the second half of January. As a result, the CPC
expects above normal precipitation for the entire forecast area
through the majority of the month. -BPN

&&

.AVIATION...04/18Z TAFs...The main hazard will be low level wind
speed shear at North Bend, Roseburg and Medford for most, if not
through the TAF period. Stronger winds have surfaced at Medford, and
is expected to last through tomorrow morning, although they will
diminish some later this evening and tonight. Peak gusts earlier
this morning reached 44 kts and it's not out of the question peak
gust could be around 40 kts. Strong winds are also likely at Klamath
Falls through the TAF period. Right now, low level wind speed shear
is not expected but it could get close tonight as surface winds
diminish slightly.

Ceilings are expected to remain VFR through the TAf period. The
exception is at Klamath Falls where light snow has resulted in
reduced visibility and lower ceilings (MVFR). However both should
improve once the precip changes from snow to rain this afternoon.
-Petrucelli

&&

.MARINE...Updated 200 PM PST Wednesday 4 January 2023...

An exceptionally strong storm will move through the coastal waters
tonight through Thursday. Winds this afternoon have reached gale
force but they will continue to strengthen and reach storm force
tonight and continue at least through Thursday morning before
gradually decreasing back to gale.

When combined with continued very steep south wind seas and fresh
swell, seas will peak Thursday between 30 and 35 feet with the
highest seas farther from shore. Large breaking seas and
exceptionally dangerous bar conditions will occur. Very high and
very dangerous seas will then continue behind the front late
Thursday into Thursday night as a long period (15 to 17 second) west-
southwest swell builds into the region.

Yet another low will build up out of the south and strengthen as it
moves towards Canada around Friday.  Gale force winds are likely
during this period.  Beyond Friday, the weather looks very unsettled
with storms strengthening over the Pacific into next week.  The
period between storms systems look fairly brief. -Smith/Sargeant

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 4 PM PST Thursday for ORZ026.

     Wind Advisory until 7 PM PST Thursday for ORZ029>031.

     High Wind Warning until 4 PM PST Thursday for ORZ030-031.

     High Wind Warning until 4 PM PST Thursday for ORZ021-022.

     High Surf Warning until 10 AM PST Friday for ORZ021-022.

     Wind Advisory until 4 PM PST Thursday for ORZ023>026.

     High Wind Warning until 4 PM PST Thursday for ORZ027-028.

CA...Winter Storm Warning until 10 AM PST Thursday above 4500 feet
     for CAZ080>083.

     High Wind Warning until 4 PM PST Thursday for CAZ081-082.

     Winter Weather Advisory until 7 PM PST this evening for
     CAZ081>083.

     Wind Advisory until 7 PM PST Thursday for CAZ083>085.

     High Wind Warning until 4 PM PST Thursday for CAZ085.

PACIFIC COASTAL WATERS...Storm Warning until 7 PM PST Thursday for
     PZZ350-356-370-376.

     Gale Watch from Friday morning through Friday evening for PZZ350-
     356-370-376.

&&

SBN/SBN/SBN