Hazardous Seas Warning 46, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
848 AM PDT FRI JUN 10 2016

.DISCUSSION...Low clouds are banking up against the mountains this
morning and we have updated the sky grids to reflect this trend.
Across northern California there is a clear area in the Scott and
Shasta Valley but otherwise sky were mostly cloudy in the lower
Klamath River Valley from Seiad Valley south. Sky is also mostly
cloudy from the Cascades east but this is due mainly to higher
clouds. The main low pressure over Vancouver Island shows little
sign of eastward movement and the frontal boundary just west of
our marine zones will remain semi-stationary throughout today
before dissipating. Onshore flow today will keep the temperatures
cool with scattered light showers.

We are still forecast tonight's low temperatures for areas east of
the Cascades to be in the lower to mid 30s. The Frost Advisory has
been issued and confidence is high that we will see those low
temperatures tonight.

The thermal trough sets up quickly along the coast with NE winds
in the coastal range and north winds for the Shasta Valley and
most of northern California this weekend. /FB

&&

.AVIATION...For the 10/12Z TAF cycle...As a front departs to the
east and an upper low approaches from the northwest, clouds are
producing a mix of MVFR and VFR cigs across the area. Everything is
expected to lift to VFR by mid morning, but scattered showers will
develop over the west side. In addition, gusty northwest winds are
expected today, especially on the east side. -Wright

&&

.MARINE...Updated 200 AM PDT Fri 10 June 2016...Relatively light
winds and seas will continue through Saturday morning as a weak
surface front and pressure trough move through. There will be a
slight chance for thunderstorms over the waters as an upper trough
passes this afternoon and evening, and gusty winds will be the
primary threat to mariners.

A thermal trough will develop along the coast Saturday afternoon and
bring moderate to strong north winds and wind driven seas to the
area south of Cape Blanco through Sunday evening. Gales are fairly
likely to occur south of Gold Beach, but there remains some question
as to how close to shore they get. The preponderance of model
guidance suggests they will get inside buoy 27, so a gale watch has
been issued from roughly buoy 27 west for Saturday afternoon through
Sunday evening. Winds gradually diminish Sunday night and Monday
morning with lighter and more variable winds continuing through the
rest of the week. A series of fronts may bring elevated winds at
times, however. Seas are expected to be mainly swell driven next
week except during frontal passages when wind waves will briefly
increase. -Wright

&&

.PREV DISCUSSION... /Issued 454 AM PDT FRI JUN 10 2016/

AVIATION...For the 10/12Z TAF cycle...As a front departs to the
east and an upper low approaches from the northwest, clouds are
producing a mix of MVFR and VFR cigs across the area. Everything
is expected to lift to VFR by mid morning, but scattered showers
will develop over the west side. In addition, gusty northwest
winds are expected today, especially on the east side. -Wright

PREV DISCUSSION... /Issued 417 AM PDT FRI JUN 10 2016/

DISCUSSION...Forecast confidence is high through Tuesday.
A Low pressure trough over the Pacific Northwest coast will be the
driver of conditions today. It will weaken as it moves inland east
to northeast on Saturday but produce a cold start to the day.
Brief ridging will bring warming Sunday then another cold upper
trough will move southeast along the Canadian coast early next
week. This trough may linger offshore for much of the
week...blocked by high pressure east of the Rockies. The
position/evolution of this low will make a big difference in the
temperature and probability of precipitation forecast. It is not
unusual to see the model differences in the long term regarding
the positioning and strength of the trough. But it can be said
that temperatures will likely be at least a little below normal
and there will be a higher than normal probability of showers.

Specifically...a weak cold front brought light rain to much of
Coos, Curry, and Douglas Counties overnight and is now tracking
across the east side. There is a slight chance to a chance that
this front will produce additional light showers over Lake County
today. It will also lead to high temperatures around a dozen
degrees cooler than yesterday. Meantime...a surface trough
associated with the axis of a cold upper level trough will sweep
eastward and bring additional light showers to the coast. There is
also a slight chance of afternoon and evening thunderstorms over
the northern portion of the coastal waters into Coos and western
Douglas Counties. There is a higher probability of thunderstorms
closer to the center of the low...into the northern Oregon coast.

The trough will move inland tonight with a slight chance of
showers north of the Umpqua Divide. Low and mid level clouds will
be extensive in that locale but mostly clear skies on the east
side will aid cooling. A frost advisory has been issued for east
side valleys on Saturday morning...quite a change from the recent
heat wave.

The probability of showers will diminish on Saturday as the trough
moves away from the area. Ridging on Sunday will lead to warming
with only scattered coverage of high clouds. Another marine push
of low clouds is expected into the coast and Umpqua Basin Sunday
night into Monday morning with the potential for light coastal
and Umpqua Basin showers or drizzle. This push will be in advance
of the next broad cold and slow moving upper trough. Most of the
area will be dry on Monday with near normal temperatures.

A series of disturbances are likely to rotate around the slow
moving trough from Tuesday into the end of the week. As mentioned
above...the timing and strength of individual waves is uncertain.
The GFS generates more rainfall during the week than the ECMWF. At
this early juncture there is little reason to favor one solution.
This will not be a pattern to produce persistent rain but it is
one to allow periods of showers.

MARINE...Updated 200 AM PDT Fri 10 June 2016...Relatively light
winds and seas will continue through Saturday morning as a weak
surface front and pressure trough move through. There will be a
slight chance for thunderstorms over the waters as an upper trough
passes this afternoon and evening, and gusty winds will be the
primary threat to mariners.

A thermal trough will develop along the coast Saturday afternoon and
bring moderate to strong north winds and wind driven seas to the
area south of Cape Blanco through Sunday evening. Gales are fairly
likely to occur south of Gold Beach, but there remains some question
as to how close to shore they get. The preponderance of model
guidance suggests they will get inside buoy 27, so a gale watch has
been issued from roughly buoy 27 west for Saturday afternoon through
Sunday evening. Winds gradually diminish Sunday night and Monday
morning with lighter and more variable winds continuing through the
rest of the week. A series of fronts may bring elevated winds at
times, however. Seas are expected to be mainly swell driven next
week except during frontal passages when wind waves will briefly
increase. -Wright

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 2 AM to 9 AM PDT Saturday for ORZ029>031.

CA...Frost Advisory from 2 AM to 9 AM PDT Saturday for CAZ084-085.

Pacific Coastal Waters...Gale Watch from Saturday afternoon through Sunday evening for
     PZZ356-376.

FJB/FJB/TRW