High Wind in Oregon, January 7, 2023

Area Forecast Discussion
National Weather Service Medford OR
936 PM PST Fri Jan 6 2023

.DISCUSSION...Radar is indicating precipitation already beginning
across portions of southern Oregon and northern California,
largely at the Coast and a few light returns east of the Cascades.
Additionally, winds remain relatively breezy across the area,
particularly in the Shasta Valley where a wind advisory will
continue overnight.

One of the changes to the forecast was to account for newer
guidance spinning up a surface low which could bring additional
winds offshore as well as increase winds somewhat at the coast.
While guidance does not suggest the damaging winds are expected at
the coast, this surface low will create the potential for a
period of gusty winds on Saturday morning at the coast (as well
as a host of marine issues). A couple of isolated spots may see a
wind gust that could produce some damage to trees or powerlines,
but it is not expected to be widespread or sustained long enough
to warrant a High Wind Warning at the coast. Otherwise, the
forecast looks well enough on track inland with the winds and
went ahead and upgraded the High Wind Watch to a Wind Wind
Warning and added additional areas of wind advisories. One of the
trickiest parts about this update package as it relates to the
High Wind warnings is that the Strongest winds will be Saturday
morning into Saturday afternoon. These winds will calm slightly,
but remain at advisory status through Saturday night. However, for
simplicity of the warning product, have gone ahead and just issued
the warning out through 12Z Sunday. Subsequent shifts can make
adjustments once the complicated nature of this system becomes a
bit simpler. For more details on the forecast, please see the
previous discussion below. -Schaaf

&&

.AVIATION...07/00Z TAFs...Mainly VFR with some areas of MVFR
prevail across the region this afternoon. Low level wind shear
remains a concern into the overnight hours as the next system slowly
pushes onshore. The coast appears the most impacted location for
wind shear as winds aloft will be quite strong, but low level wind
shear is expected at all TAF locations west of the Cascades sometime
during the next 24 hours. Winds at about 2200 feet will be about 60
knots over the waters. Terrain obscurations will continue through
the TAF period, with cigs gradually lowering to MVFR from west to
east as the front pushes inland tonight into Saturday. Local areas
of IFR are possible in heavy rain. /BR-y

&&

.MARINE...Updated 900 PM PST Friday 6 January 2023...Strong
south winds will result in gales through Saturday morning. High
resolution models are showing a quick moving, compact surface low
moving through the waters early Saturday morning. While gales are
likely, there is the potential for a brief period of storm force
winds between 5 and 40 nm from shore between 3am and 7am local time
Saturday morning. If storm force winds materialize, expect very
steep and chaotic wind driven seas.

Winds will ease briefly Saturday afternoon, but remain strong into
next week as multiple fronts pass through the region. Seas remain
elevated, but become less steep for a brief period Saturday as the
period lengthens. Another front approaches the waters Saturday
evening and south winds increase again and could approach gales
Saturday evening into Sunday. With increased swell combining with
increased wind waves Hazardous Seas Warning criteria are possible
over all the waters Saturday evening into Sunday night. /BR-y

&&

.PREV DISCUSSION... /Issued 229 PM PST Fri Jan 6 2023/

SHORT TERM...Through Sunday Night...A warm front has moved
onshore and is directing a moisture plume on shore. This is
bringing showers to the area, one band along and east of the
Cascades, the other moving onshore now. Some isolated showers also
exist outside of these main bands as well. Amounts in the past
six hours from this current front are at 0.1" to 0.2" in the
Cascades and Siskiyous and less than 0.1" everywhere else. At the
moment road cameras show overall dry conditions and support these
more sparse rain accumulation observations.

As the warm front continues to push onshore the snow level will
hover between 5000 and 5500 feet. Precipitation amounts will pick
up in the coming hours as well, though most of the precipitation
will remain over NorCal. With the heavier precipitation rates in
NorCal, the snow level may drop at times down to 4500 feet. In
Siskiyou County, there is a winter storm warning for above 4500
feet to highlight the winter impacts. Please read the Winter Storm
Watch product for more details (WSWMFR).

As the cold front, currently well offshore, moves towards the
coast later this evening, winds will continue to increase. A wind
advisory is out for the Shasta and southern Rogue valley, as well
as a high wind warning for the coast. Driving conditions could
become difficult for high profile vehicles and weak tree branches
may fall.

These wind and snow impacts will continue into Saturday morning
with another warm and cold front right behind it. Snow levels have
trended down behind the cold front with this next system and
precipitation amounts again are expected to be focused along the
coast and over NorCal. We have issued a winter storm watch for
almost the same area of NorCal, except above 3000 feet this time.
In addition, this system will again bring gusty winds and we have
issued high wind watches for the Shasta Valley and higher terrain
of the East Side. We will wait for the warnings and advisories in
effect currently to drop before we upgrade the current watches.
There may also be a need for further wind advisories in the
greater area of the Shasta Valley and in the southern end of the
Rogue Valley.

With both today's series of fronts and tomorrow's, we expect rain
shadowing to occur in the west side valleys. So if you plan to
travel over the passes, do not be fooled by what is expected to be
dry conditions. Check the forecast and plan for at least lightly
wet, winter weather driving conditions.
-Miles

LONG TERM...(Monday through Friday). The pattern will
remain active for the foreseeable future with a parade of systems
moving  the area. The pattern that has set up over the Pacific
remains fairly consistent with systems lined up as far west as the
Aleutians.

The main challenge during this time will be the timing, intensity,
and track of each individual upper low trough, surface fronts and
surface low pressures. The main change from what was discussed
yesterday are that there is better clarity among the operational
ECMWF, GFS and there respective individual ensemble members.

Right now it looks like Sunday nights/Mondays storm will be the
strongest of the lot in terms of precipitation and winds. Even then
the bullseye of the precip will be in northern California, and
perhaps the southern coastal range. These areas have the best chance
of getting moderate to occasionally heavy precipitation from Sunday
night into Monday afternoon, although precipitation could end up
diminishing Monday afternoon along the coast and south coastal
range.

Another, but weaker storm will be on the heels of Mondays' storm and
impacting mostly northern California, however precipitation amounts
are not expected to be as significant, and it should not be as
windy.

Snow levels during this time will fluctuate, especially during
periods of when the warm front moves through where they can end up
around 5000 feet, followed by the cold front where they could lower
to around 4000 feet. Areas above 5000 feet are likely to have some
travel impacts. Thats' not to day areas above 4000 wont't but the
chances will be diminished some.

We'll catch "relative" break in the action as short wave ridging
builds in Tuesday night into Wednesday, before the next system
arrives bringing increasing precipitation and gusty winds.

One thing to note: A large upper trough west of Wednesday's system
is expected to dig which could result in the bulk of the
precipitation to remain along the coast and offshore Wednesday night
through Thursday, then by the time it makes its way inland we could
see a flow split which typically puts a cap on the amount of
precipitation and less concern for wind.

There is "some" evidence supporting the continued wet and windy
pattern through at least the middle of the month, followed by a
pattern change for the latter part of the month with troughing
developing in the eastern part of the U.S. with riding building over
the Pacific Northwest. A different data set (showing the same
parameters) were not as convincing yesterday, but today it's showing
some promise. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 AM to 10 PM PST Saturday for ORZ029.

     High Wind Warning from 7 AM Saturday to 4 AM PST Sunday for
     ORZ030-031.

     Wind Advisory from 7 AM Saturday to 4 AM PST Sunday for ORZ030-
     031.

     Wind Advisory from 7 AM Saturday to 4 AM PST Sunday for ORZ026.

CA...Winter Storm Warning until 4 PM PST Saturday above 4500 feet for
     CAZ080>083.

     Winter Storm Watch from Saturday afternoon through Sunday
     morning above 3000 feet for CAZ080>083-085.

     Wind Advisory until 7 AM PST Saturday for CAZ081.

     High Wind Warning from 7 AM Saturday to 4 AM PST Sunday for
     CAZ081.

     Wind Advisory from 7 AM to 10 PM PST Saturday for CAZ084.

     High Wind Warning from 7 AM Saturday to 4 AM PST Sunday for
     CAZ085.

     Wind Advisory from 7 AM Saturday to 4 AM PST Sunday for CAZ085.

PACIFIC COASTAL WATERS...Gale Warning until 7 AM PST Saturday for
     PZZ350-356-370-376.

     Small Craft Advisory from 7 AM to 10 PM PST Saturday for PZZ350-
     356-370-376.

     Hazardous Seas Watch from Saturday evening through late Sunday
     night for PZZ350-356-370-376.

&&