Hazardous Seas Warning 8, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
259 PM PST Thu Feb 2 2017

.DISCUSSION...We'll catch a relative break in terms of precipitation
this evening. The next impulse is offshore and this will reach the
coast early this evening and move onshore tonight. The main short
term concern will be winds. Gusty south winds are already occurring
in the Shasta Valley and portions of the Rogue valley with the
strongest winds near Ashland. Winds have picked up at Medford
recently and that has allowed the temperature to shoot up to 61
degrees. South winds will increase in both these areas tonight and
there is the potential for them to reach high wind criteria in the
portions of Shasta Valley later this evening through Friday night.
Gusty winds are also expected east of the Cascades, but not until
later tonight. Details on the wind products can be seen at NPWMFR.

As previously mentioned the next impulse will bring another round of
precipitation to the coast and coastal mountains early this evening,
then moving inland tonight. Followed be a second one late Friday
morning into Friday afternoon. Snow levels are expected to be around
5500 feet tonight, then may lower to around 5000 feet Friday
afternoon as the upper trough moves towards the coast bringing in a
cooler air mass. However it looks like most of road snow concerns
will be confined to the Diamond Lake and Crater Lake areas,
therefore have adjusted the winter weather advisory to this area.
Please see WSWMFR for more details. Snow will also accumulate in the
higher terrain in Siskiyou county, but they should remain above all
the passes. Because of this, have canceled the winter weather
advisories.

The highest precipitation totals from this evening through Friday
night are expected to be along the coast, coastal mountains, western
through southern Siksyou County and northern Cascades.

A large upper low west of Vancouver Island will continue send several
disturbances through the area Friday night through Saturday evening.
This will continue a wet onshore southwest flow aloft with higher
precipitation amounts Saturday into Saturday night...especially west
of the Cascades. Snow levels are expected to remain around 5000 to
5500 feet.

The models suggest a brief break is possible Sunday morning as weak
ridging builds ahead of an approaching shortwave trough, but
difference exist with respect to the details and timing. If nothing
else, showers will be far and few in between Sunday morning before
another round of moderate to heavy precipitation arrives at the
coast Sunday afternoon. Of note, the models show a surface low
moving northeast towards Oregon, but they disagree with the track.
THE GFS brings the surface low into central Oregon while the ECMWF
and NAM bring it into northwest Oregon. This is important because it
could have an effect on where the strongest winds will be,
especially over the marine waters and coast. For now leaned towards
the NAM, ECMWF solution, but confidence on this solution is low, so
watch for updates on this. -Petrucelli

...Long Term...Monday through Thursday Night...The blocking ridge
over Alaska will be the primary source of uncertainty regarding the
forecast during the extended term, as the models have not been
handling systems moving around or under this ridge very well. As a
result, model runs over the past several days have been very
inconsistent with the timing and strength of various waves and
frontal systems. While confidence in details remains low, the
general pattern does remain consistent. The forecast area will
remain under cyclonic flow aloft, and with several shortwaves
traversing or undercutting the ridge upstream, there will be periods
of showers and wind. Have therefore kept at least a slight chance of
precipitation in the forecast during each period, with higher
chances here and there to illustrate the best chances for passing
systems.

Snow levels and temperatures have also swung back and forth with
each subsequent run. The latest model tuns are producing a colder
air mass over the area Monday night into Tuesday morning, followed
by much warmer temperatures Wednesday into Thursday. The resulting
forecast places snow levels down to almost 1500 feet Tuesday
morning, then well above all but the highest peaks by Wednesday
evening. This is a new pattern in the model suites, so will need to
monitor the next few runs and update as necessary. -BPN

&&

.AVIATION...02/18Z TAF Cycle...Conditions are expected to remain
mostly VFR west of the Cascades, though isolated pockets of MVFR
ceilings and visibilities could accompany showers into this
afternoon. On the East side, periods of light snow and MVFR are
expected this morning and afternoon in upslope areas, mainly along
and near the Cascades. Later this evening and tonight, an
approaching frontal system will spread precipitation and gusty winds
across the region, with MVFR/IFR and terrain obscuration becoming
widespread. -BPN

&&

.MARINE...Updated 230 PM PST Thursday 2 February 2017...
Winds will strengthen and shift to the south over the next 12 hours
as a frontal system approaches the region. Very steep seas will
affect areas beyond 10 nm from shore initially...then southerly to
southwesterly gales are expected Friday with very steep seas closer
to shore.

Southerly gales are expected Friday morning with a likely brief
decrease in wind speeds early Friday afternoon before another round
of gales arrive late Friday afternoon and evening as the low center
pushes towards the coast.

Gales diminish Friday night but the pattern will remain
active into early next week with another strong front and possible
gales Sunday. Confidence is increasing in gales on Sunday, and we'll
be considering issuing gale watches or warnings in the next few
shifts. SK

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 1 AM Friday to 4 PM PST Saturday for
     ORZ030-031.
     Wind Advisory from 1 AM Friday to 4 PM PST Saturday for
     ORZ030-031.
     Winter Weather Advisory from 10 PM this evening to 10 AM PST
     Saturday ABOVE 500 FEET for for ORZ027.
     Wind Advisory until 4 PM PST Friday for ORZ026.

CA...High Wind Warning from 1 AM Friday to 4 PM PST Saturday for
     CAZ085.
     Wind Advisory from 1 AM Friday to 4 PM PST Saturday for CAZ085.
     High Wind Warning until 4 AM PST Saturday for CAZ081.
     Wind Advisory until 4 AM PST Saturday for CAZ081.

Pacific Coastal Waters...Hazardous Seas Warning from 4 AM Friday to 10 PM PST Saturday
     for PZZ350-356.
     Gale Warning from 4 AM Friday to 1 AM PST Saturday for
     PZZ350-356-370-376.
     Small Craft Advisory for hazardous seas until 4 AM PST Friday
     for PZZ350-356-370-376.
     Small Craft Advisory for hazardous seas from 1 AM to 10 PM PST
     Saturday for PZZ350-356-370-376.
     Hazardous Seas Warning until 10 PM PST Saturday for PZZ370-376.