Hazardous Seas Warning 66, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
943 AM PDT SUN SEP 18 2016

.UPDATE...
Updates to the forecast for today through this evening have been
made and sent. These updates were to adjust precipitation
probabilities upward across portions of Douglas and Coos Counties
where precipitation is being observed and generally downward south
of Roseburg and Crater Lake National Park. Cloud cover has been
scaled back for much of the day, as well, for areas east of the
Coast Range and south of the Umpqua. High temperatures have been
nudged upward due to the expectation of lesser cloud cover. BTL

&&

.DISCUSSION...
Rainfall amounts overnight through this morning have been up to
0.28" at Charlotte Ridge and 0.10" to 0.20" at some other locations
Coos County. Otherwise, just a few hundredths have been observed
in portions of Curry, Douglas, and Coos Counties eastward up to
about the northwestern edge of Crater Lake National Park.

For the rest of today, short range model guidance and model trends
indicate the front today will be weak and primarily along the
edges of our land area, with rain and mostly cloudy conditions
remaining confined to the areas along and west of the Coast Range
and from the Cascades westward north of Crater Lake National Park.
Thus, for most inland areas in our area, it will be another very
warm and dry late summer day, albeit breezy late this afternoon
and evening. BTL

&&

.AVIATION...18/06Z TAF CYCLE...IFR/LIFR ceilings and visibilities
are expected along the coast into Sunday morning with occasional
light rain or mist. Lower conditions will also push into the Umpqua
Valley by 12z, but probably MVFR at KRBG. Some light rain will also
spread into areas north of the Umpqua Divide and to the Cascades
north of about Mt. Mcloughlin. Improvement is expected during the
afternoon to MVFR at the coast and VFR inland. The rest of the area
will remain VFR with just some high and mid level clouds. -DW

&&

.MARINE...Updated 230 AM PDT Saturday 17 September 2016...A cold
front will move onshore this morning. South winds ahead of the front
will veer to northwest by late morning. Seas will build and become
dominated by moderate west swell of 6 to 8 ft at 14 to 15 seconds.
Areas of steep seas are expected to develop late this afternoon and
and continue into early Monday for areas south of Cape Blanco.
Monday afternoon, gusty north winds will develop with winds
increasing to small craft advisory levels for areas south of Cape
Blanco. With continued west swell of 7 to 8 feet at 12 to 13 seconds
combined with building short period wind chop, expect a mix of steep
to very steep seas to develop south of Cape Blanco. The most
hazardous conditions are expected from Gold Beach southward from 5
to 40 nm from shore. Winds and seas may lower slightly on Tuesday
and Wednesday. -CC

&&

.FIRE WEATHER...230 AM Sunday 18 September 2016...A cold front
will move over the area today and brings a cooler and more humid
airmass in from the north and west. Some showers are possible along
the coast and into the Umpqua valley and Southern Oregon Cascades
today with this front. Gusty west winds are expected from the
Cascades eastward late this afternoon and this evening. Tuesday, an
upper trough will move towards the area then move inland on
Wednesday. This trough will bring additional cooling and a slight
chance of showers Tuesday night and Wednesday. Also expect
additional gusty winds from the Cascades east during the afternoons
and evenings Tuesday and Wednesday. With the trough remaining in
place through Thursday, expect a continued cool and more moist air
mass. Also expect a slight chance for showers over east side areas
on Thursday. -CC

&&

.PREV DISCUSSION... /Issued 316 AM PDT SUN SEP 18 2016/

DISCUSSION...With the main belt of Westerlies lying over the
Pacific Northwest, and a cold front brushing by just to our
north, conditions are ripe for precipitation. Despite the radar
currently overshooting much of the action, current observations
from several sites along the coast show rain is indeed occurring.
Up to 0.25" of rain could fall along the Coos and Douglas coasts
by late this morning, with locally heavier amounts in the coastal
mountains. The Cascades north of Crater Lake could receive just as
much through this afternoon, but the south coast and the Umpqua
basin are only likely to see a few hundredths. The rest of the
region should remain dry, but increased cloudiness and slightly
cooler temperatures will be noticeable just about everywhere
within the forecast area.

Model solutions continue to show all of the energy and moisture
associated with the swift upper level flow remaining well to our
north tonight through Tuesday. Due to this, the forecast area will
remain dry, with a gradual cooling trend throughout. A cold front
will slide through the region Tuesday, while an upper level low
digs south and takes up residence overhead by Wednesday morning.
This should result in a drastic drop in temperatures for Wednesday
and Thursday. The frontal passage looks mostly dry at this point,
but a few model runs are hinting at the potential for showers over
the higher terrain Tuesday evening through Thursday as the trough
deepens, closes off, then slides to the east. Snow levels look
like they will drop into the 6kft to 7.5kft range Wednesday night
and Thursday, so it is possible that the high peaks could see a
dusting should the showers materialize. The cold air may also
bring the first frost of the season to many of the West Side
valleys midweek, but that will depend greatly on whether or not
the skies clear overnight.

Ridging is then expected to build in over the area for the weekend
once the trough departs. However, there is a possibility of some
light precipitation along the coast and into the Umpqua and northern
Cascades Friday night into Saturday morning, as the trialing end of
a front, associated with a low pressure center far to our north,
deals the forecast area a glancing blow. Otherwise, with the ridge
overhead and thermal troughing to our south, it seems as though we
will return to a warm and dry pattern for the remainder of the
forecast term. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

Pacific Coastal Waters...
- Hazardous Seas Watch from Monday afternoon through Monday
  evening for PZZ356.
- Hazardous Seas Watch from Monday afternoon through Tuesday
  morning for PZZ376.
- Small Craft Advisory for hazardous seas from 5 PM this
  afternoon to 2 PM PDT Monday for PZZ376.

BTL/BPN/CC