High Wind in Oregon, December 11, 2021

Area Forecast Discussion
National Weather Service Medford OR
353 AM PST Sat Dec 11 2021

.DISCUSSION...Winter weather moving in this morning and
significant impacts are likely across much of NorCal and SW Oregon
through next week. Snow is still expected to be measured in feet
through next week in the mountains above about 3000-4000 foot
elevations during this time period and lower in the Mount Shasta
area. Additionally, Monday night through Thursday, lower elevation
snow will be possible. Please see our web page, social media, and
the discussion, below, for further details.

A strong frontal system has moved into the forecast area with
increasing winds along and near the coast. A High Wind Warning
is in effect for portions of the coast today. A High Wind Warning
and some wind advisories are in place for some areas east of the
Cascades into early Sunday morning. Wind advisories are are in
effect some lower elevation areas of the east side, as well.

Winter storm warnings are in effect for much of Siskiyou County
as well as the Oregon Cascades and Siskiyous for 10 to 20 inches,
but locally much higher amounts, for Saturday afternoon through
Sunday afternoon. Snow levels are likely to be in the 2500-4500
foot range during this time period and heavy, wet snow is likely
in the Mount Shasta area. We also expect significant snowfall
impacts in the Weed area in NorCal, on Siskiyou Summit, along
Highway 140 near Lake of the Woods, and in the Crater and Diamond
Lake areas down to between 3kft and 3.5 kft Saturday afternoon
through Sunday.

Winter storm watches in NorCal have been upgraded to warnings
from Sunday evening through Monday evening for portions of
Siskiyou County, including the Mount Shasta area, as another wave
of low pressure moves through the area and focuses on Northern
California. Snow levels Sunday night into Monday are likely to
rise a bit, into the 3500 to 4500 foot range, and snow could,
therefore, change to rain for some of that time period in and near
Mount Shasta City. Also, additional significant snowfall is
likely in other areas of SW Oregon through Tuesday, though the
focus of the heaviest snow is likely to remain in the Mount Shasta
area.

Monday night through Thursday ensembles indicate the possibility
of a couple more low pressure systems, but have differed on the
details, especially related to how far inland moisture makes it
with cold temperatures in place. From Monday night through
Wednesday there is a possibility of impacting low elevation
snowfall for areas west of the Cascades, to include the lower
valleys of Jackson and Josephine counties.

&&

.AVIATION...11/12Z TAFs...From the Cascades west...VFR
conditions are expected at the start of the TAF period with low
level wind speed shear at Roseburg and Medford. Ceilings will lower
to MVFR with the higher terrain becoming obscured as precipitation
develops as a cold front pushes into the area, especially from the
Umpqua Divide north. Medford will continue to see VFR ceilings into
this afternoon, but the higher terrain could be partly obscured
after 20z. Low level wind shear will diminish this morning as
surface winds increase. The exception will be Roseburg where it
could persist into the afternoon hours. Tonight, MVFR and occasional
IFR conditions are expected until the end of the TAF period.

East of the Cascades...VFR conditions will prevail through the
morning, but higher terrain will become obscured late this morning.
Low level wind shear will be a concern until the stronger winds
surface around 19z at Klamath Falls. The TAF shows gusts to around
30 kts late this afternoon, but they could end up higher, close to
35 kts. MVFR conditions are expected this evening through the end of
the TAF period as precipitation in the form of snow moves into the
area. -Petrucelli

&&

.MARINE...Updated 200 AM PST Saturday 11 December 2021...Moderate to
strong south winds are being observed ahead of a strong cold front
which are expected to continue for most of the morning. Gale force
winds are likely with gust up to storm force this morning. Winds
will shift from south to southwest as the front pushes south through
the waters late this morning through the afternoon. Once the winds
shift southwest, they will diminish below gales, but very steep and
hazardous seas will persist as a long period northwest swell builds
into the waters this afternoon into Sunday. This swell will peak
Sunday night at 15 to 18 feet at 16 seconds.

Low pressure will send another front through the waters and onshore
Sunday night into Monday. Steep seas will persist over the waters
early next week. Another strong front will approach the waters
Tuesday night and move onshore Wednesday morning with moderate to
strong south winds expected ahead of the front, shifting southwest
and diminishing once the front moves onshore Wednesday morning.
-Petrucelli

&&

.BEACH HAZARDS...Updated 200 AM PST Saturday 11 December 2021...A
high surf advisory remains in effect beginning at 4 PM PST Saturday
and lasting through 4 PM PST Monday. An incoming long period high
WNW swell will bring breaker heights in the surf zone of 20 to 25
ft, increasing the risk for high surf at area beaches Saturday
evening through Monday evening. These large breaking waves will
create hazardous conditions along and within the surf zone, and
could inundate beaches and low lying shorelines. Beach erosion is
possible, and exposed infrastructure may be damaged. Jetties are not
the place to be in these situations, stay far away from them.
-Spilde/Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 10 AM this morning to 4 PM PST
     Sunday for ORZ028>031.
     Winter Storm Warning from 10 AM this morning to 4 PM PST Sunday
     for ORZ027-030.
     High Wind Warning until 10 AM PST Sunday for ORZ031.
     Wind Advisory until 10 AM PST Sunday for ORZ031.
     High Wind Warning until 4 PM PST this afternoon for ORZ021-022.
     High Surf Advisory from 4 PM this afternoon to 4 PM PST Monday
     for ORZ021-022.
     Winter Storm Warning from 10 AM this morning to 4 PM PST Sunday
     above 3500 feet in the for ORZ025.

CA...Winter Weather Advisory from 10 AM this morning to 4 PM PST
     Sunday for CAZ083>085.
     High Wind Warning until 10 AM PST Sunday for CAZ085.
     Wind Advisory until 10 AM PST Sunday for CAZ085.
     Winter Storm Warning from 10 AM this morning to 10 PM PST Monday
     for CAZ080-081.
     Winter Storm Warning from 1 PM this afternoon to 10 PM PST
     Monday for CAZ082-083.

Pacific Coastal Waters...
     High Wind Warning until 4 PM PST this afternoon for PZZ356.
     Gale Warning until 4 PM PST this afternoon for
     PZZ350-356-370-376.
     Hazardous Seas Warning from 4 PM this afternoon to 4 PM PST
     Monday for PZZ350-356-370-376.

SBN/SBN/SBN