Gale Warning 5, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
854 AM PST Tue Jan 15 2019

.DISCUSSION...It is a quiet morning across southern Oregon and
northern California, but RADAR imagery shows an area of light
precipitation is making its way north into Siskiyou, Josephine,
and Curry counties. Meanwhile, fog has developed in the Umpqua
basin, the Illinois Valley, and the Rogue Valley near Grants
Pass. Have made a few adjustments to the forecast to account for
these factors, but no major changes were made. All other aspects
of the forecast look good this morning, so no other updates are
necessary.

Major focus of efforts this shift will be the upcoming snow, wind,
and surf that will arrive late today into Thursday. Currently,
several weather watches are in effect, and these will likely be
upgraded today. For more information on these and the rest of the
forecast, see the previous discussion below. -BPN

&&

.AVIATION...For the 15/12Z TAFs...Areas of LIFR cigs/vsbys in low
clouds and fog over portions of the Illinois Valley, Grants Pass
area, and the Umpqua Valley including KRBG this morning.
Expect the lower conditions to clear to VFR from late morning
through mid-afternoon.

Elsewhere, VFR conditions will persist into this afternoon. Then,
areas of MVFR cigs will spread into the area from the southwest
late this afternoon/tonight. Higher terrain will become obscured.
There will also be MVFR/IFR vsbys in areas of snow. -Spilde

&&

.MARINE...Updated 830 AM PST Tuesday 15 January 2019...South winds
and wind waves will increase late this morning over the outer
waters.  Then this evening, they will move in closer to shore
creating conditions hazardous to small craft.

Much stronger low pressure offshore will bottom out around 970 mb
near 43 N and 131 W Wednesday afternoon and will send a strong cold
front through the waters Wednesday night, then onshore Thursday.
This will likely bring a period of south gales Wednesday afternoon
into Thursday. Heavy west swell and wind waves peaking at 25 to 30
feet will bring chaotic seas, high surf and dangerous bar crossings
to the area during this interval that will subside late Thursday
night.

Yet another front though will move through Friday night into
Saturday, bringing another round of high winds and heavy seas to the
area. -Spilde/Smith

&&

.PREV DISCUSSION... /Issued 431 AM PST Tue Jan 15 2019/

DISCUSSION...Mostly quiet weather prevails over the forecast
area this morning. Radar indicates some light returns east of the
Cascades, and webcams show some light snow showers around the Bly
area. Fog and low clouds persist in the Umpqua Basin, and some
patchy fog is beginning to develop in the Illinois Valley.

Low pressure that has been lingering offshore the past few days
will move north through the area today, and today will be a
transition day back to a more active pattern. Snow levels will
start around 3500 feet this morning, rising to around 4000 feet
this afternoon. Precipitation will be relatively light and mostly
confined to northern California and along the coast. Snow levels
will hover just above Mount Shasta City proper, but surrounding
locations could see some light accumulations through this
afternoon, including Black Butte and Snowmans Summits where 1 to 3
inches will be possible.

The main event is expected Wednesday into Thursday morning.
Southerly flow will continue, and a stronger system will move into
the area. Strong winds and heavy snow will be the main concern
here. Strong southerly flow will bring ample amounts of moisture
to portions of Northern California and snow levels will hover
around 4500 to 5000 feet. Periods of moderate to heavy snow are
likely late Wednesday morning into Thursday morning. A Winter
Storm Watch remains in effect during this time period. It looks
like the period of heaviest snow is possible late Wednesday
afternoon and evening when 700 mb southerly flow of 55 to 65 kt
peaks before turning southwest to westerly later Wednesday night.
Snow levels look high enough to spare Mount Shasta City proper of
heavy snow, but it's not out of the question if perception rates
are high enough to see some snow mix down to around 4000 feet
during this time. The Cascades and Siskiyous will get their fair
share of snow as well, and it's possible some Winter Weather
Advisories will be needed.

Strong winds will be a concern with this storm as well. A High
Wind Watch remains in effect for portions of the Coast, east of
the Cascades, and the Shasta Valley. While pressure gradients
indicate high wind potential along the coast, the offshore
component north of Cape Blanco will limit the strength of the
winds there. So the best potential for strong winds remains south
of Cape Blanco. Inland, pressure gradients peak around -6.0 to
-7.0 mb and this typically equates to fairly breezy conditions in
the Rogue Valley as well as the Shasta Valley. Advisories will
likely be needed outside of the watch area for Wednesday afternoon
and evening.

In addition to possible strong winds and heavy snow, periods of
moderate to heavy rain are expected in the Coastal Mountains and
portions of western Siskiyou county. Three to four inches is
expected from late Wednesday morning through Thursday evening.
We're not expecting any flooding concerns at this time, but it
will be something to keep an eye on.

Beyond Thursday, a warm front will nudge it's way into the area as
ridging briefly passes over the forecast area. Active weather will
continue through the weekend. /BR-y

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Watch from Wednesday afternoon through Thursday
     afternoon for ORZ030-031.
     High Wind Watch from Wednesday afternoon through Thursday
     afternoon for ORZ021-022.

CA...High Wind Watch from Wednesday afternoon through Thursday
     afternoon for CAZ085.
     Winter Storm Watch from Wednesday morning through late Thursday
     night for CAZ080>083.
     High Wind Watch from Wednesday morning through Thursday
     afternoon for CAZ081.

Pacific Coastal Waters...Gale Watch from Wednesday morning through Thursday evening for
     PZZ350-356-370-376.
     Small Craft Advisory until 10 AM PST Wednesday for PZZ370-376.
     Small Craft Advisory from 4 PM this afternoon to 10 AM PST
     Wednesday for PZZ350-356.