Small Craft Advisory 2, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
1000 AM PST Thu Jan 4 2024

Updated AVIATION Section

.DISCUSSION...A Winter Storm Watch /PDXWSWMFR/ has been issued for
early Saturday morning into Saturday evening at elevations above
2500 feet in Josephine, Jackson, eastern Douglas, far western
Klamath, and western Siskiyou counties. Snowfall of 5 to 12
inches is expected for the Cascades and Siskiyou Mountains. The
foothills will have a wide range of 2 to 10 inches expected, with
the higher amounts just a bit higher in elevation, above 3000
feet. Meantime, amounts of 1 to 5 inches are expected Saturday for
the remainder of Siskiyou County above 2500 feet, and areas east
of the Cascades.

Immediately behind this cold frontal passage, the lowest snow
levels of the season so far are expected with a relatively lengthy
period of lighter snow showers, occurring mainly in Oregon, late
Saturday night into Sunday evening. Snow levels are forecast to
drop from 2500 feet Saturday evening to around 1500 feet early
Sunday morning, then nudge up to 2000 to 2500 feet with the modest
heating of the day as snow showers taper off late Sunday
afternoon. During this second event, particularly during Sunday
morning, an accumulating snow of an inch or two is expected for
the northern Josephine/southern Douglas County passes on
Interstate 5, east Medford, and Ashland. Meantime, the southern
Oregon Cascades and Siskiyou Mountains are forecast to receive an
additional Advisory level accumulation of 2 to 6 inches.

There is also a High Surf Advisory /PDXCFWMFR/ in effect for
southern Oregon beaches from early Friday morning to early Sunday
morning. Please see the Beach Hazards section below.

First, a weakening warm front will move across our area today,
then the trailing cold front tonight, with light to locally
moderate precipitation. The snow level is rising from around 4000
feet up to 5500 feet today, then falling to as low as 3000 feet by
the time the last few showers end late tonight. Precipitation
amounts at around a tenth of an inch to a half inch will be
highest in western Oregon. The higher intensity precipitation is
expected mainly on the west facing slopes of the Oregon Cascades.
Up to a tenth of an inch of precipitation is expected elsewhere in
our area.

High pressure on Friday will provide the only real break in the
weather during the next week. This will result in favorable
conditions for valley low clouds and fog, particularly on the west
side during the late night and morning. Otherwise, high clouds
will arrive late in the afternoon in advance of Saturday's
impactful frontal system.

Beyond Sunday, a very brief break between systems is expected
Sunday night, with valley low clouds and fog into Monday morning.
Another warm front is expected to spread rain to the coast and
Coast Range by the start of Monday morning. This disturbance is
likely to result in another episode of light to locally moderate
precipitation on Monday, mainly in Oregon, while snow levels rise
to around 5000 feet.

Forecast confidence drops a notch from Monday night onward. But,
there is a high likelihood of a continued wet, active pattern at
least into Friday. After Monday's warm front, the trailing cold
front of uncertain (but likely stronger) strength is likely Monday
night into Tuesday. This will likely be not quite as cold as
Saturday's front, with the highest probability for snow levels
falling to around 3000 feet. Like the aftermath of its weekend
predecessor, there is a potential for both a trailing trough
around Tuesday night or Wednesday, and another trough around
Thursday into Friday to be characterized by much colder air with
low snow levels/the potential for additonal snow, including in
some west side valleys.

&&

.AVIATION...04/18Z TAFs...Weak warm advection is bringing plenty of
cloud cover over the area this morning with areas of MVFR/IFR, light
rain and widespread terrain obscuration. Freezing levels will be
mostly 4500 to 6000 feet. A weak cold front will push through from
NW to SE later this afternoon and tonight and this should result in
lowering freezing levels, but also with precipitation decreasing
from NW to SE. Low-level moisture will linger behind the front with
some low clouds/fog (IFR/MVFR) remaining or forming in the
stabilizing air mass. Best chance for lower ceilings/fog is over the
west side valleys. -Spilde

&&

.MARINE...Updated 230 AM Thursday January 4, 2024...Steep seas in
all waters are going to continue today under the influence of
continuing westerly swell. Wave heights will increase slightly on
Friday morning as long-period swell arrives in all waters. A frontal
system arriving on Saturday morning will further unsettle the seas
as well as bringing gusty winds that will continue into Saturday
night. Currently northwest winds of 20 to 25 kts with gusts up to 35
kts are expected in all waters through the day Saturday. Peak seas
look to be 15 to 18 feet at 16 to 17 seconds.

A current Small Craft Advisory has been extended until Friday at 10
PM to reflect continuing steep seas. Steep or very steep and
hazardous seas are expected to continue with the arrival of the
front on Saturday morning. Current outcomes would have a short
period of very steep and hazardous seas in waters beyond 30 nm from
shore for a short time. Additional observations and guidance will
help to solidify the timing and impact of the arriving front.

Seas will decrease through Sunday and Monday under stable
atmospheric conditions and lower swell. Long term guidance shows
conditions deteriorating rapidly on Tuesday morning due to an
impactful front moving over the area from the northwest. -TAD

&&

.BEACH HAZARDS...Updated 230 AM Thursday, January 4 2024...A
long period swell will arrive Thursday night and continue through
the weekend. Current projections show peak seas of 13-17 feet at 19
seconds on Friday morning. On Saturday, an approaching front will
bring gusty northwest winds, building peak seas of 15-20 feet at 17
seconds Saturday morning and continuing into the evening. This will
increase the risk for high surf along all southern Oregon beaches. A
High Surf Advisory will be in place from Friday at 4 AM through
Saturday at 10 PM to reflect hazardous conditions along southern
Oregon beaches. This pattern of steep swell and active weather will
likely bring dangerous conditions to all area beaches. -CC/TAD

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Watch from late Friday night through Saturday
     evening above 2500 feet for ORZ024>026.

     High Surf Advisory from 4 AM Friday to 4 AM PST Sunday for
     ORZ021-022.

     Winter Storm Watch from late Friday night through Saturday
     evening for ORZ027-028.

CA...Winter Storm Watch from late Friday night through Saturday
     evening above 2500 feet for CAZ080.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 PM PST Friday
     for PZZ350-356-370-376.

&&