Small Craft Advisory 100, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
400 PM PDT TUE OCT 11 2016

.SHORT TERM...
Winds... Wind headlines have been updated for the upcoming storm
system Thursday into Friday. Please see our web page and/or the
bottom of this page for further details. Specifically, strong winds
will begin to affect the area late Thursday morning, peaking at the
coast late Thursday afternoon and evening. High wind warnings have
been issued for the coast south of Bandon, as well as for the Shasta
Valley, and portions of the East Side. Advisory level winds are also
expected for much of the East Side and the Rogue Valley.

Regarding forecast confidence in warning level winds, confidence
is highest along and near the coast, with gusts over 60 mph
expected. In the Shasta Valley the rain spilling over from the
Mount Shasta upslope zone may cause frictional drag on the winds,
which could limit winds to below the 58 mph gust warning
threshold. However, more likely than not, these winds will occur
at some point during the warning period at Weed Airport or
Montague. For the wind advisories across the East Side and the
Rogue Valley confidence in advisory level winds is moderate to
high on the east side and low to moderate in the Rogue Valley. In
short, the strength of the south winds coming over the Siskiyous
could keep winds from reaching advisory criteria in the Rogue
Valley. Currently, there appears to be a 3 to 6 hour window
late Thursday afternoon to early evening where wind gusts of 45 to
55 mph are possible on from about the center of the valley
northeastward. For all areas, given that this is the first
significant wind event of the season and leave are still on the
trees in many areas, the potential for downed tree limbs and power
line is increased.

After a relative lull Friday, winds are expected to ramp back up
for another round of wind on par or possibly greater than the
first storms system for Saturday through Sunday as remnants of a
Western Pacific Ocean typhoon get ingested into the storm track
into the Pacific Northwest.

A third, but likely weaker, but still fairly strong, frontal
system is expected Monday into Tuesday. BTL

.LONG TERM...Thursday through Tuesday morning...We have no
significant changes to the expected big pattern shift toward very
active, windy, wet weather beginning Thursday, continuing through
the weekend and lasting into early next week. Confidence in this
pattern change is very high. The main forecast challenges will be
how much rain will occur and the potential for flooding, as well as
how strong winds will be. Several strong fronts will move onshore
from the Pacific during this time frame, each of which will bring
strong, gusty winds and very heavy rainfall. Rain amounts during
this stretch will likely be more than we would typically see during
the entire month of October! Expected total precipitation (QPF) from
Thursday morning to sunrise Monday morning is 10-15 inches in the
Brookings area and the Curry Coastal Mountains, 5-10 inches in other
portions of the coastal counties, 3-6 inches in much of Douglas
County and the Cascades and Siskiyous, 5-7 inches in the Mount
Shasta area, 2-3 inches in the usually drier Bear Creek portion of
the Rogue Valley and Central and Northern Shasta Valley, and 1-3
inches on the East Side. If we get the expected 5-day precipitation
total we currently have in the forecast for the Medford Airport, it
would be the wettest 5-day period in the month of October in Medford
since 1962.

Since we are coming out of the dry season, many area rivers, creeks
and strems are running very low and therefore, can absorb a lot of
this moisture. However, with it coming in such a short period of
time, we expect some shorter term hydrological concerns, with the
possibility of flooding/slides on or near recent burn scars and in
areas where drains clog from fall debris. Right now, it's a good
idea to prepare for the incoming rainfall by cleaning gutters and
storms drains to lessen the risk of them backing up.

We'll also have some very strong winds with these storms. Thursday
through Friday morning high winds will be possible along the coast,
in the Shasta Valley and over the mountains, as well as in the
Summer Lake area. Advisory level winds are possible in portions of
the Rogue Valley from parts of Ashland to Medford during that time
period, as well. Please see the high wind product (NPWMFR), which
outlines the details concering this first high wind event.
Additional windy periods are anticipated from successive storm
systems, primarily Saturday and possibly again early next week, so
stay tuned for updates regarding those.

Snow levels look to be above 8kft for the bulk of this precipitation
event, but could dip to near 7kft in heavier bursts of precipitation
and on the tail end of individual frontal systems through Saturday
night. Sunday through Monday snow levels are expected to lower to
near 6kft. Anyone planning to venture onto the Cascade Peaks should
very much take this into consideration, as white-out conditions and
high winds at or above hurricane force above treeline, will occur,
at times.

Beyond that, model guidance is indicating that we'll get a break
around the middle of next week as a ridge aloft builds in. This may
present the opportunity for frost/freeze concerns on the west side
at some point. Spilde/BTL

&&

.AVIATION...11/18Z TAF CYCLE...Expect mostly VFR conditions
during the day with skies scattering and light winds under high
pressure at all TAF sites. Early Wednesday morning, expect coastal
fog and low stratus supported by moist southerly winds and high
pressure aloft. In the Umpqua Basin, expect IFR to LIFR
conditions...whether due to low stratus or to fog is uncertain and
depends on the amount of surface mixing. Elsewhere...expect VFR and
light winds through the TAF period. -MSC

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 230 PM PDT Tuesday, October 11, 2016...
Weak high pressure builds remains over the area tonight, then slides
east tomorrow as the first in a series of fronts approaches. This
will result in continued relatively light winds and seas through
tomorrow.

Confidence is high a series of storms will move through the water's
Thursday through next weekend. Winds will become south and increase
as the first front approaches Wednesday. The models show low
pressure developing along the front Wednesday night, then rapidly
deepen as it moves from the southwest to northeast Thursday
afternoon. There are still differences among the models regarding
the track and strength of the low, but either way, at least gale
force winds will occur over much of our waters Thursday afternoon
and evening. There is also concern that the low could deepen enough
to produce storm force winds in a strong coastal jet just prior to
frontal passage Thursday evening. Confidence on this is not quite
high enough to upgrade the watch to a warning, so we'll keep the
gale and storm watches going. In addition the wind, seas will be
extremely dangerous with at least 20 to 25 foot wind waves expected,
and some guidance suggests seas over 30 feet.

There may be a relative break in winds and seas Friday, but they
will still be at least small craft advisory level over much of the
area. Then an even stronger low may move by to our north and produce
even stronger winds and higher seas Saturday. While this storm could
be worse than the first, in order to avoid confusion, we'll continue
to cover it with a marine weather statement as opposed to additional
watches. If current trends continue, expect further watches to be
issued for the Saturday storm. -Wright/Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 2 PM Thursday to 5 AM PDT Friday for
     ORZ029>031.
     Wind Advisory from 11 AM to 2 PM PDT Thursday for ORZ029>031.
     High Wind Warning from 11 AM to 11 PM PDT Thursday for
     ORZ021-022.
     Wind Advisory from 11 AM to 11 PM PDT Thursday for ORZ026.

CA...High Wind Warning from 2 PM Thursday to 5 AM PDT Friday for
     CAZ085.
     Wind Advisory from 11 AM to 2 PM PDT Thursday for CAZ084-085.
     High Wind Warning from 2 PM to 11 PM PDT Thursday for CAZ081.

Pacific Coastal Waters...
- Gale Watch from late Wednesday night through Thursday evening
  for PZZ356-376.
- Storm Watch from late Wednesday night through Thursday evening
  for PZZ350-356-370-376.

BTL/MAS/DW/Petrucelli