High Wind in Oregon, November 18 to 19, 2016

Area Forecast Discussion
National Weather Service Medford OR
320 PM PST Fri Nov 18 2016

.SHORT TERM...A front is located about 150 miles off the Southern
Oregon coast. This front will gradually move inland across the
area tonight and Saturday morning. Ahead of and with the frontal
passage expect strong gusty winds over portions of the area. Also
southwest portions of the area, mainly Curry and Siskiyou
counties, will see moderate to heavy precipitation.

South winds have increased this afternoon in the Shasta Valley,
over the mountains and for areas east of the Cascades. South winds
have also begun to increase in the southern Rogue Valley. As a jet
aloft moves into the area this evening and tonight and the surface
pressure gradient increases, expect winds gusts up to 65 mph in
the southern Shasta Valley with winds gusting to 45-50 mph in the
Rogue Valley. Winds will increase during the evening and remain
strong overnight and into Saturday morning. Winds are expected to
lower behind the front late Saturday morning and Saturday
afternoon but remain breezy. East of the Cascades strong gusty
winds are likely over the mountains, including the Warners, Hart
Mountains and Summer Rim area, and in the Paisley to Silver Lake
area with winds peaking late this evening through Saturday
morning then continued gusty winds into Saturday night and Sunday
morning as another weaker jet max move into the area. For details
on the winds see the NPWMFR.

As the front moves inland tonight, moderate to heavy precipitation
is forecast into Curry and Siskiyou counties. Heavy precipitation
amounts around the Mount Shasta in south central Siskiyou county
combined with lowering snow levels will bring winter storm
conditions. Due to upslope effects from very moist air and a mid
level jet, snow levels are expected to lower to 4000 feet in the
Mount Shasta area during the evening then down to near 3500 feet
elevation late tonight and early Saturday morning. Snow
accumulation of 5 to 10 inches is expected above 3500 feet
elevation for southern Siskiyou County with higher amounts above
6000 feet elevation. Of note, a heavy wet snow is expected for
the 3500 to 4000 ft elevations and snow accumulations may vary
significantly with some areas seeing more and other less. This may
be of most concern near Mount Shasta City where snow accumulations
around 4 to 7 inches are possible. For mountain passes such as
near Snowmans Summit on highway 89, expect greater snow
accumulations tonight through Saturday with accumulations around 6
to 12 inches. For details on the winter storm warning conditions
see the WSWMFR for details.

West of the Cascades in Southern Oregon expect snow levels to
remain fairly high around 5000 to 5500 feet with a mix of light to
moderate precipitation. Over the Siskiyous and from the Cascades
east in Southern Oregon as well as into Modoc County expect snow
levels to lower to around 4000 to 4500 feet tonight and Saturday
morning with light precipitation. This will result some light snow
accumulation possible especially over the mountains.

Behind the front, an upper level trough moves into the region
Saturday afternoon through Sunday night. Shortwaves embedded in
this trough will move into the region late Saturday through Sunday
bringing additional precipitation with snow levels varying from
around 4500 to 5500 feet. During this period expect the focus for
precipitation to be from the coast into Siskiyou County for this
period but all areas will see period of light or moderate
precipitation.

Lastly, behind the frontal passage and with the upper trough
expect instability over the coastal waters with a slight chance
for thunderstorms tonight through Saturday.

Early next week, expect a break in the pattern with a shortwave
upper level ridge moving into the region late Monday with
diminishing shower chances over the area. This break in the active
pattern is expected to be brief though.

.LONG TERM...Tuesday through Friday Night...Models are in good
agreement regarding the wet and active pattern during the long term.
While there are some variations in the strength and timing of the
individual features, there is much less uncertainty regarding the
overall pattern. It would be very safe to say that the area will see
a continuation of the wet weather through the remainder of next
week.

Very deep troughing over Siberia will throw off several waves
during the week, each passing across the north Pacific in quick
succession. The first of the three systems expected during the long
term will arrive on Tuesday, followed by another Wednesday night
into Thanksgiving, and yet another Friday night. Each system will
have a brief break in between, but in some cases, this will be
barely noticeable. There are no particularly telling features
appearing in any of the model suites that would single out any of
these system as particularly strong or exceptional, but this could
easily change in coming model runs. For now, have trended the wind
and rain forecasts during each system towards values typical with
our normal wet season storms, with heavy rain and gusty winds at the
coast, and strong winds across the East Side and in the Shasta
Valley.

One item of note will be snow levels, which are expected to hover
between 3000 and 4000 feet throughout the week. This would mean that
each system will likely produce snow at most of our area passes.
This is particularly concerning when considering the upcoming busy
holiday travel. Those planning on traversing the area next week
would do well to stay up to date with the latest forecasts and make
the necessary plans to account for the likelihood of wintry weather.
-BPN

&&

.AVIATION...18/12Z TAF cycle...Areas of IFR cigs/vsbys will prevail
for most of the morning in the Umpqua Basin and portions of the
Rogue and Illinois Valley. VFR conditions should return to most
areas between 17-18z. A strong front will approach the region this
afternoon and evening, and pass overhead tonight. Ceilings will
gradually lower along the coast later this evening then inland
tonight with terrain gradually becoming obscured. Gusty south to
southeast winds will develop in the Shasta Valley, portions of the
Rogue Valley and over the east side this afternoon and evening.
There may be a period of low-level wind speed shear at North Bend
late this morning into this evening. There is also concern for wind
speed shear at Roseburg and Medford this evening and tonight. Once
the front passes, MVFR to IFR conditions are possible in the West
Side valleys, but confidence is low and will depend on winds and mid
to higher level cloud cover. Conditions should improve late in the
TAF period, but not significantly. -BPN/Petrucelli

Note: The ceilometer at FAA site KOTH is out of service, so there
will be no ceiling observations available generally between the
hours of 04Z and 14Z.

&&

.MARINE...Updated 200 PM PST Friday 18 November 2016...A strong cold
front has now moved inside 130W and will move through the waters
this evening then onshore early tonight. A scatterometer pass
earlier today showed widespread gales occurring ahead of the front,
so gales are certain over the vast majority of our waters over the
next 3 to 12 hours. We will probably also see a few hours of high end
gales and storm force gusts as a coastal jet forms just as the front
approaches the coast late this evening. Winds will drop below gales
later tonight as the front moves onshore, but seas will remain very
steep due to a mix of wind wave and fresh swell. Gales will redevelop
tomorrow afternoon and evening as another low pressure system moves
inside 130W and pushes a front toward the coast.

We will see a break in winds and seas Monday, but another front
brings south gales and very steep seas Tuesday. The stormy pattern
continues for the foreseeable future with cold fronts roughly every
other day all the way into next weekend. -Wright

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 10 PM this evening to 10 AM PST Sunday for
     ORZ026-030-031.

CA...Wind Advisory from 10 PM this evening to 10 AM PST Sunday for
     CAZ081-085.
     Winter Storm Warning from 10 PM this evening to 10 AM PST
     Saturday ABOVE 3500 FEET for for CAZ080>083.
     High Wind Warning until noon PST Saturday for CAZ081.

Pacific Coastal Waters...Small Craft Advisory until 4 AM PST Sunday for PZZ356.
     Gale Warning until 4 AM PST Sunday for PZZ350-356-370-376.

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