High Wind in Oregon, October 15, 2016

Area Forecast Discussion
National Weather Service Medford OR
514 AM PDT SAT OCT 15 2016

.SHORT TERM...Today through Monday night. This will be a good
weekend to stay indoors. The big picture of the short term
forecast is consistent with the previously issued forecast. A
strong storm will impact our area this morning into this evening
with hazardous/damaging winds, high surf, a slight chance to
chance of thunderstorms, and moderate to heavy precipitation.
There is the potential for flooding where rain will be heaviest.
That will be much the same area that had the heaviest rain with
the storm on the day before yesterday...Coos, Curry and western
Josephine County. There is also the potential for flash flooding
in burn scarred areas of western Siskiyou County.

A rapidly strengthening cyclone is now centered offshore near 41N
130W. It will continue to strengthen through the day while
tracking northeast to Vancouver Island. The strongest southerly
winds and highest rainfall rates will accompany the frontal
passage at the coast between 8 AM and Noon with gusts of 80 to 100
MPH forecast at headlands and sustained winds of 35 to 50 MPH
elsewhere in the coastal zones. The snow level will be near 7000
feet as the front tracks inland and inland winds reach their peak
during the late morning and afternoon. Inland winds will range between
advisory and warning strength with the strongest winds over the
higher terrain, in the Shasta Valley, east side Valleys, and the
southern portion of the Rogue Valley. These winds will be strong
enough to produce downed limbs and trees that may produce power
outages.

While the focus has rightly been on today's extreme weather, a
cold front to follow on Sunday will pack it's own wallop with its
main impact in the form of additional moderate to heavy
precipitation. The cumulative impact of the series of storms could
produce new or additional flooding at the coast and Josephine
County. Compared to today's system, the parent low will be farther
from our coast and weakening rather than strengthening as it much
more slowly moves east toward Vancouver Island. This will result
in winds that will not be as strong, though still noticeably
breezy to windy during the day-time and evening hours. Between
the two storms from today through Sunday night, the coastal
locations that received 3 to 7 inches of rain on Thursday are
forecast to receive an additional 4 to 10 inches of rain.
Elsewhere in southern Oregon, 48 hour amounts of around 2 to 4
inches are expected. Also, 1 to 2 inches of rain on the east side,
and 2 to 8 inches in western and central Siskiyou County with the
highest amounts in the far western and southern portions of the
county. The snow level on Sunday will be around 6000 feet and fall
to 5500 feet as showers decreasing in number on Sunday night.

A slow moving upper level trough will remain anchored off the
coast of Canada through Monday night then move inland on Tuesday.
It will send a series of disturbances eastward across our area
with frequent showers that will run the gamut from weak to
moderate to strong intensity.

.LONG TERM...Tuesday through Saturday. The 00Z GFS and ECMWF are
in good agreement through Thursday night on a transition to a
pattern of active but not stormy weather. An upper level trough
and associated front will move across the Pacific Northwest on
Tuesday. This will produce light precipitation across most of the
area...except occasional moderate intensity in the morning in Coos
and Douglas Counties where the highest rainfall amounts will
occur. The models have trended weaker with ridging that is
expected to build northeastward from offshore of southern and
central California on Tuesday night. With a stabilizing air mass,
coastal and west side valley low clouds will develop into
Wednesday morning as well as a slight chance of mainly coastal
light over-running drizzle/showers. The GFS indicates colder
valley low temperatures on Wednesday morning, which may be
moderated a bit more than the model indicates due to the valley
low clouds.

The ridge will push the storm track farther north. On Wednesday, a
warm front looks to reach southwest Oregon with a slight chance
to chance of light showers...with the highest probability once
again for the coast and Douglas county. The ridge is expected to
build Wednesday night into Thursday. The strengthening of the
ridge should result in less cloud cover, colder morning low
temperatures, and warmer afternoon high temperatures rising to a
few degrees above normal. But, an inversion is likely to lead to
patches of mainly west side valley morning low clouds and fog.

Model agreement rapidly deteriorates beyond Thursday night. The
ECMWF solution flattens the ridge somewhat but keeps it
sufficiently strong to maintain dry weather into the end of the
week. Meantime, the GFS suggests a stronger trough in the Gulf of
Alaska will more substantially weaken and kick the ridge farther
inland. The GFS would keep the storm track aimed north of our
area, but the southern end of the first in a new series of fronts
could brush our area. As a result, a slight chance of showers is
forecast in Coos and Douglas counties and the temperature forecast
has been nudged down a bit to be closer to normal.

&&

.AVIATION...15/06Z TAF CYCLE...MVFR conditions within showers
will continue through tonight. We've also observed some lightning
along the coast, and more is possible through this evening.

As we move into Saturday, wind shear will be a concern as the next
storm system approaches. Clouds and winds will increase through the
early morning hours, with very high winds arriving at the coast by
mid morning. These winds will then spread across the rest of the
area, along with heavy rain, and persist through much of the day.
Expect lowered flight conditions, strong winds, heavy rain, and
mountain obscurations across the region, with mountain wave
turbulence likely along and east of the Cascades. The front will
move onshore late Saturday afternoon and will move out to the
east of the area late Saturday night. Winds will diminish...but
areas of MVFR cigs will develop behind the front from the Cascades
west Saturday night.

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 AM PDT Saturday, October 15, 2016...The latest
forecast is on track with another very strong storm affecting the
area today. This is from the remnants of typhoon Songda and is
quickly moving along in a fast wind flow aloft. It's going to deepen
rapidly and bring a chance of thunderstorms as it recurves to the
north off the Pacific Northwest coast this afternoon. We expect
strong Storm Force winds with gusts up to and above Hurricane
Force across all of the coastal waters as the storm passes
through. Waves will also become very high and steep. Although
winds will weaken behind the front, seas will remain very high and
steep through Sunday, only gradually weakening through the first
half of next week. -FB

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 11 AM this morning to 2 AM PDT Sunday for
     ORZ029>031.
     Wind Advisory from 11 AM this morning to 2 AM PDT Sunday for
     ORZ029>031.
     High Surf Warning until 11 AM PDT Sunday for ORZ021-022.
     High Wind Warning until 5 PM PDT this afternoon for ORZ021-022.
     Flood Watch through this evening for ORZ021-022-024.
     Wind Advisory from 8 AM this morning to 8 PM PDT this evening
     for ORZ023>026.
     High Wind Warning from 8 AM this morning to 8 PM PDT this
     evening for ORZ027-028.
     High Wind Warning from 8 AM this morning to 8 PM PDT this
     evening for ORZ026.

CA...High Wind Warning from 11 AM this morning to 2 AM PDT Sunday for
     CAZ084-085.
     Wind Advisory from 11 AM this morning to 2 AM PDT Sunday for
     CAZ084-085.
     Wind Advisory from 8 AM this morning to 8 PM PDT this evening
     for CAZ080>082.
     Flash Flood Watch from 11 AM PDT this morning through this
     evening for CAZ080.
     High Wind Warning from 8 AM this morning to 8 PM PDT this
     evening for CAZ081.
     High Wind Warning from 8 AM this morning to 8 PM PDT this
     evening for CAZ083.

Pacific Coastal Waters...High Surf Warning until 11 AM PDT Sunday
     for PZZ350-356.
     Storm Warning until 8 PM PDT this evening for PZZ350-356-376.
     Hurricane Force Wind Warning until 8 PM PDT this evening for
     PZZ350-356-370-376.
     Hazardous Seas Warning until 5 AM PDT early this morning for
     PZZ350-356-370-376.

DW/FJB/CZS