Hazardous Seas Warning 73, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
932 AM PDT TUE OCT 25 2016

.UPDATE...A cold front that passed over the area overnight is east
of the Medford forecast area and has weakened. Several lightning
strikes were observed over the marine waters this morning due to
some lingering instability...expect any convection to diminish in
the next few hours.  Elsewhere, showers will continue this morning,
then decrease this afternoon, giving a short break in weather. A low
pressure system will move inside of 130W this evening. Expect
stratiform rain along the coast and coastal mountains as the
associated warm front passes over...and gusty winds in areas. The
forecast challenge for today will be determining how far east rain
will occur tonight... and the strength of winds this evening and
tonight. See previous discussion below for more information. -MSC

&&

.AVIATION...25/12z TAF cycle...IFR/LIFR in some of the valleys west
of the Cascades, including the terminal at KMFR, should lift to VFR
by late this morning. The remainder of the area will be MVFR or
better today with scattered showers near the coast, the adjacent
coastal waters and portions of the east side. An area of low
pressure will bring steady rain back to western Siskiyou County, the
coast and the coast ranges tonight with MVFR cigs/vis and terrain
becoming obscured west of the Cascades. However, downslope southeast
winds should keep VFR at KMFR with just isolated to scattered
showers. East side areas should also remain VFR. -Spilde

Note: The ceilometer at FAA site KOTH is out of service, so there
will be no ceiling observations available generally between the
hours of 04Z and 14Z.

&&

.MARINE...Updated 245 AM PDT Tuesday, October 25, 2016...South gales
and very steep seas this morning, especially north of Gold Beach,
will ease this afternoon and evening. However, conditions will
remain hazardous to small craft. Another storm will arrive from the
southwest tonight into Wednesday with another round of gales and
steep to very steep seas. Expect winds and seas to gradually subside
Wednesday night into Thursday, then remain low through Friday. The
next front will move in with increasing south winds and steep seas
Friday night into Saturday. -Spilde

&&

.PREV DISCUSSION... /Issued 510 AM PDT TUE OCT 25 2016/

DISCUSSION...25/00Z NAM/GFS/EC in.

The northern hemispheric pattern shows a wave number of five
around the globe. This is normally a progressive pattern, but with
a deep nearly cutoff trough off the west coast, progress will be
slow, at least initially.

That trough will remain in roughly the same location through this
week and beyond, as short waves diving down the back side of it
will force it to maintain its position. As long as it remains out
there, the Pacific Northwest will remain under southwest and
occasionally south flow aloft, and short waves ejecting from the
trough will push fronts onshore through the period. It will remain
relatively wet, but high temperatures will be 5 to 15 degrees above
normal for the most part. The exception will be the coast and
Umpqua Basin, where temperatures will be near normal.

The next short wave will move through the area Tuesday. The
associated front will be weak. It will move onshore Tuesday
morning, but retreat back offshore as an upstream system develops.
It will bring some gusty winds to the area though, and a Wind
Advisory will be issued for the Shasta Valley and some locations
east of the Cascades. Those winds will peak Tuesday night, then
diminish Wednesday afternoon.

The following short wave will move up from the south Wednesday...
but most of the associated energy will remain offshore and to the
north of the Medford CWA. The associated front will move onshore
Wednesday morning and become stationary through Wednesday night.
The coast and Coast Range will get significant rain from this
system, but not much will fall inland.

Yet another wave will move in Thursday. This one will come in from
the west and the energy is directed farther south. This will
reinforce the stationary front and this front will push inland
Thursday. Precipitation will move inland as well, but there won't
be a lot of it.

Another wave will come up from the south Thursday night into
Friday. This system won't be very windy, but it will bring quite a
bit of precipitation to the area beginning Thursday night.

Long term discussion from the Monday afternoon AFD...Friday
through Monday. Models start this time frame in fairly good
agreement with a closed 500 mb low at 39 N and 136 W at the same
indicated 544 height. This first system of the extended period
brings rain ahead of a warm front Saturday. The models remain in
good agreement as the upper low moves down to about 100 nm
offshore of Northern CA. This brings the triple point of this
system directly over our forecast area Sunday. From there, models
are in broad agreement with a deep upper level trough over the
coastal waters off of the Pac NW, and the timing of systems will
be impossible this far out and have broad-brushed chance pops
through the remainder of the extended. -Sven

AVIATION...25/12z TAF cycle...IFR/LIFR in some of the valleys west
of the Cascades, including the terminal at KMFR, should lift to VFR
by late this morning. The remainder of the area will be MVFR or
better today with scattered showers near the coast, the adjacent
coastal waters and portions of the east side. An area of low
pressure will bring steady rain back to western Siskiyou County, the
coast and the coast ranges tonight with MVFR cigs/vis and terrain
becoming obscured west of the Cascades. However, downslope southeast
winds should keep VFR at KMFR with just isolated to scattered
showers. East side areas should also remain VFR. -Spilde

Note: The ceilometer at FAA site KOTH is out of service, so there
will be no ceiling observations available generally between the
hours of 04Z and 14Z.

MARINE...Updated 245 AM PDT Tuesday, October 25, 2016...South gales
and very steep seas this morning, especially north of Gold Beach,
will ease this afternoon and evening. However, conditions will
remain hazardous to small craft. Another storm will arrive from the
southwest tonight into Wednesday with another round of gales and
steep to very steep seas. Expect winds and seas to gradually subside
Wednesday night into Thursday, then remain low through Friday. The
next front will move in with increasing south winds and steep seas
Friday night into Saturday. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 11 PM this evening to 8 PM PDT Wednesday for
     ORZ029>031.

CA...Wind Advisory from 11 PM this evening to 8 PM PDT Wednesday for
     CAZ083-085.
     Wind Advisory from 8 PM this evening to 5 PM PDT Wednesday for
     CAZ081.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT this evening for
     PZZ350-356-370-376.
     Gale Warning from 2 AM to 2 PM PDT Wednesday for PZZ350-356-370.
     Gale Warning from 11 PM this evening to 2 PM PDT Wednesday for
     PZZ376.

MSC/JRS/MAS