Gale Watch 3, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
243 PM PST Mon Feb 6 2017

.DISCUSSION...Current satellite and radar images are already showing
the white of the eyes with precipitation already starting to reach
the northern California/southwest Oregon coast. This will increase
over time and will spread into northern California early this
evening and later this evening and tonight in Oregon. Colder air is
still in place and snow levels are lower. This will result in the
potential for significant snow in northern California early this
evening and later this evening for the Oregon Cascades and eastside.
Thus have issued a winter storm warning for portions of these areas.
The timing of when the warm from moves through and snow levels come
up will is going to be a key factor in storm total snow. For
example, if the warm front lifts north quicker, then snowfall
accumulations will end up lower than what's currently forecast.
Right now, the models are in pretty good agreement with the timing
of the warm frontal passage. In addition we could be looking at a 4-
6 hour period of heavy snow with snowfall rates anywhere between 1-3
inches per hour in the Siskiyous, Cascades, portions of the eastside
and the Warners east of Alturas.

The tricky part west of the Cascades is whether or not we'll get any
snow down to the lower passes north of Medford tonight. Model
guidance is divided in just how low snow levels will be, with the
GFS/ECMWF staying up above 2500 feet for the event. The NAM12 is
notably colder as precipitation arrives this evening and with some
wet-bulb effect expected, heavier precipitation rates could lower
the snow level more than the global models indicate. Right now, it
looks like there could be a slushy inch of wet snow at Sexton,
Smith, Stage Road and Canyon Creek passes before precipitation
changes to rain by Tuesday morning. It isn't out of the realm of
possibility that we see snow reach all the way down to places like
Hayes Hill Summit and Barton Road on I-5, which are both closer to
1500 feet. These areas have all been known to do that from time to
time. Please see NPWMFR for more details.

Once the warm front moves through, snow levels will shoot up rather
quickly to 6500 to 7000 feet early to mid morning Tuesday in
northern California and late morning or early afternoon in Oregon
and snow will quickly change over to rain. Precipitation will
gradually decrease Tuesday afternoon and we should catch a relative
break in rainfall Tuesday night into early Wednesday morning.

Another round of moderate to heavy precipitation with tropical
connection could impact the area Wednesday afternoon through
Wednesday night. Snow levels will be high, so the only areas that
may get impacted from road snow should be around Crater Lake. Also we
could be dealing with another round of moderate to strong winds at
the coast and east of the Cascades. This is still a ways out so the
details could change. there could be a concern for flooding on
creeks and streams. Mainstem rivers will heed to be monitored
closely. Given we have several headlines out, decided to hold off
on any wind headlines at this time. -Petrucelli

.Long Term...Friday through Monday...By Friday, the atmospheric
river from the short term will have sagged well south of us.
However, the main upper low and its attendant secondary cold front
will move through Friday and bring another round of moderate
precipitation. Snow levels will be much lower than preceding days,
dropping to 4500 feet Friday morning and then 3500 feet by day's
end. This may lead to some travel issues from snow in the mountain
passes and portions of the east side. An end to our latest spate of
stormy weather is in sight by next weekend, however, as an upper
ridge builds in over the PacNW. It looks like a dry and potentially
mild weekend coming up depending on the amount of fog and low cloud
we get in the valleys. -Wright

&&

.AVIATION...06/18Z TAF Cycle...Conditions will remain unsettled
behind a cold front today. Expect showers and occasional MVFR
conditions to be mostly confined to the mountains, coast, and Umpqua
basin today. Gusty winds will affect most areas this afternoon. A
strong warm front will bring moderate to heavy rain and MVFR to IFR
conditions to west side locations (including KRBG and KMFR) tonight
into Tuesday morning. Conditions may not be quite as poor at KOTH
due to downsloping and offshore winds, but confidence is lower
there. In the mountains above 2500 feet and across the east side
(including KLMT) moderate to heavy snow with IFR to LIFR conditions
will develop tonight and continue into Tuesday morning. -Wright

&&

.MARINE...Updated 230 AM PST Monday 6 February 2017...Very steep
hazardous seas dominated by wind seas and fresh swell will continue
through early this morning then very steep hazardous seas will
mainly affect areas north of Cape Blanco this morning and afternoon
with steep seas elsewhere. Southwest winds are expected to increase
during the morning and into the afternoon and reach small craft
advisory levels across the waters. Winds will lower this evening and
seas will gradually lower below small craft advisory levels tonight.
Another strong front is expected to bring strong winds and building
seas Wednesday night and Thursday. South winds may rise to gale or
storm force with this front Wednesday night and Thursday.
Additionally, very steep hazardous seas of 16 to 22 feet dominated
by wind seas and fresh swell are possible. Weaker fronts will follow
Thursday night into Friday. /CC

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 10 PM this evening to 10 AM PST
     Tuesday for ORZ029>031.
     Winter Storm Warning from 10 PM this evening to 10 AM PST
     Tuesday for ORZ029>031.
     Winter Weather Advisory from 10 PM this evening to 10 AM PST
     Tuesday ABOVE 2000 FEET for for ORZ023>026.
     Winter Weather Advisory from 10 PM this evening to 10 AM PST
     Tuesday for ORZ027-028.
     Winter Storm Warning from 10 PM this evening to 10 AM PST
     Tuesday for ORZ027-028.

CA...Winter Weather Advisory from 7 PM this evening to 7 AM PST
     Tuesday for CAZ082.
     Winter Storm Warning from 7 PM this evening to 7 AM PST Tuesday
     for CAZ082.
     Winter Weather Advisory from 7 PM this evening to 7 AM PST
     Tuesday ABOVE 3500 FEET for for CAZ080-081.
     Winter Weather Advisory from 7 PM this evening to 7 AM PST
     Tuesday for CAZ083>085.
     Winter Storm Warning from 7 PM this evening to 7 AM PST Tuesday
     for CAZ083-085.

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