Small Craft Advisory 36, NWS Medford, OR

Area Forecast Discussion...Corrected
National Weather Service Medford OR
1205 AM PDT Mon Apr 9 2018

Corrected time for Marine section...

Updated Aviation and Marine...

.UPDATE...Current observations are showing mostly clear skies
across the area. Temperatures today will be well above normal, but
we're likely not looking at many records. That being said, one or
two of our climate sites may come close to record values. That
being said, the current forecast looks on track, and have made no
changes for this update.

The main challenge for this forecast will be refining the winds
for the advisory tonight and tomorrow, as well as the snow
forecast for Wednesday. -Schaaf

&&

.AVIATION...09/18Z TAF CYCLE...
VFR conditions will prevail under thin cirrus clouds through this
evening. A strong, but weakening, cold front will increase southerly
winds tonight into Tuesday, greatest along and near the coast and
from the Cascades eastward. A brief period of low level wind shear
is possible around the time of frontal passage in the 12Z-18Z time
frame, mainly along the coast. Partial terrain obscurations are
expected, especially from the Cascades westward, Tuesday morning.
Valley areas away from the coast will experience VFR and localized
MVFR with and shortly after frontal passage. MVFR is expected, at
times, Tuesday morning along and near the coast. BTL

&&

.MARINE...Updated 830 AM PDT Monday, 9 April 2018...
High pressure over the area, centered inland, will continue to
weaken this evening. A strong cold front will bring a period of gale
force winds to portions of the coastal waters late tonight into
Tuesday morning. The remainder of the area will see small craft
advisory conditions. Seas will remain hazardous after the winds
subside. Another cold front will move through Wednesday with another
round of gales for some of the area. Heavy west swell will develop
behind the front, and seas will peak Thursday night around 20 feet
at 16 seconds. BTL

&&

.PREV DISCUSSION... /Issued 504 AM PDT Mon Apr 9 2018/

DISCUSSION...The main forecast change was to issue a Wind
Advisory /NPWMFR/ from early Tuesday morning through Tuesday
afternoon for portions of Lake County, eastern Klamath County, and
eastern Modoc County. This includes the Winter Rim, Warner
Mountains, and Highway 31 from Paisley to Silver Lake. Also, a
slight chance of thunderstorms has been introduced to the coastal
waters and immediate coast on Wednesday night.

There will be an active, wet and windy weather pattern for the
next week with breaks expected today through this evening, Tuesday
night, and Friday afternoon through Saturday night. It will be
unusually warm and dry this afternoon with highs around 10 to 20
degrees above normal. Southerly winds increase and precipitation
is likely to develop early Tuesday ahead of a cold front. The
front will weaken as it moves inland. The next frontal system will
then affect the area Wednesday through Thursday with higher
precipitation amounts and snow levels falling from around 5500
feet to 2500 feet msl. A warm front will brush past to the north
late Thursday night through Friday with light rain, mainly in
southwest Oregon. The next frontal system is then likely on Sunday
into Monday.

The forecast from now through Thursday is largely consistent with
the inherited forecast. The bulk of precipitation with the first
front will be light and occur during Tuesday morning through
early Tuesday afternoon with snow levels falling from around 6500
to around 5000 to 5500 feet msl. A couple of shortwaves in the
southwest flow aloft may bring a very light shower or two on
Tuesday night, mainly near the coast.

Model agreement on timing and strength has improved regarding the
next cold front that will pass through the area Wednesday morning
into Wednesday evening. One change is that the GFS and NAM have
trended slightly weaker with associated southerly wind speeds.
That said, portions of the east side may still receive another
bout of advisory strength southerly winds. Light to moderate
precipitation still looks to be widespread with heavy rain for
Curry County into western portions of Josephine and Siskiyou
Counties. A showery air mass will follow Wednesday night through
Thursday with the potential for an advisory level snowfall in
portions of the Cascades and Siskiyou Mountains.

There is also better model agreement on the timing and strength of
the warm frontal passage late Thursday night through Friday, and
also the strength of ridging on Saturday. Rain will be focused
north of our area, but the highest amounts in southern Oregon will
likely be in Coos and western Douglas Counties. It is looking
more likely that all of southwest Oregon and northern Klamath
County would at least have a measureable amount of very light
overrunning rain on Friday morning. High pressure will follow
with rapidly improving conditions likely on Friday afternoon.

Model agreement decreases beyond Saturday. But, the pattern looks
to turn active yet again with a cold front Sunday into Sunday
night and a showery post-frontal air mass early next week.

AVIATION...09/12Z TAF CYCLE...VFR conditions will prevail into
Monday evening, except for patchy IFR cigs/vsbys in fog early this
morning in some of the valleys.  Areas of MVFR cigs in rain and fog
will develop over the coastal water Monday evening, spreading to the
coast and Coast Range Monday night with higher terrain becoming
obscured.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 4 AM to 5 PM PDT Tuesday for ORZ030-031.

CA...Wind Advisory from 4 AM to 5 PM PDT Tuesday for CAZ085.

Pacific Coastal Waters...Small Craft Advisory from 2 AM to 11 AM PDT
Tuesday for      PZZ350-356-370-376.      Small Craft Advisory for
hazardous seas from 11 AM to 11 PM PDT      Tuesday for PZZ350-356-
376.      Gale Warning from 2 AM to 11 AM PDT Tuesday for PZZ350-356-
370-376.      Hazardous Seas Warning from 11 AM to 11 PM PDT Tuesday
for      PZZ350-356-370-376.

BMS/BTL/DW