Small Craft Advisory 2, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
831 PM PST Sun Jan 6 2019

.DISCUSSION...Radar observations are showing light rain and snow
occurring over portions of Siskiyou and Modoc Counties in
California as well as most of Klamath and southern Jackson
Counties in Oregon. Meanwhile, a few light showers are occurring
in Josephine County as well as north of the Umpqua divide and the
Coast. The snow level has teetered most of the day, but is
generally going to land to be around 1500 to 2500 feet now that
the sun has set and precipitation will be coming to an end in the
next couple of hours.

Will be allowing the winter weather products (WSWMFR) continue, as
precipitation is not completely finished yet, and because we are
still expecting partial clearing tonight. This clearing could
allow temperatures to fall near or below freezing in many areas
(Roseburg, Elkton, and at and near the Coast are the
exceptions). This can lead to wet roads freezing and becoming
slippery. If you must travel overnight, please take extra
precautions. But it is safer to travel tomorrow once temperatures
rise above freezing. Regardless, am not making changes to the
forecast; and have left the previous discussion below which
details the ongoing active pattern quite well. -Schaaf

&&

.PREV DISCUSSION... /Issued 345 PM PST Sun Jan 6 2019/

Updated aviation discussion.

DISCUSSION...Showers will continue over most of the area through
this evening due to instability as cold air aloft moves overhead and
plenty of shortwave activity moves through. The upper trough is now
over the area and will remain there through this evening.

Another disturbance will arrive later this afternoon into this
evening which will enhance precipitation over most of the area. The
main concern this evening will be the potential for snow near 1500
feet west of the Cascades which will affect the passes on I-5
between Grants Pass and Canyonville, Hayes Hill Summit and
Jacksonville Hill. The general consensus is we could be dealing with
a 4-6 hour period of showers that could be moderate at times. The
concern is that any moderate shower could result in snow
accumulating on roads during this time period.

Late this evening and tonight, showers will decrease, but the
concern will then shift from accumulating snow to wet or slushy
roads icing up as temperatures drop near or below freezing,
especially if there's any clearing. This could result in difficult
driving conditions tonight through the morning commute. Because of
the above mentioned reasoning, the decision was made to make
adjustments to the Winter Weather Advisory west of the Cascades to
include areas above 1500 feet and put the end time at 9 am pst
despite the fact showers are expected to end before then. Confidence
on the snow levels and snow amounts west of the Cascades this
evening are low to medium. Upslope westerly flow should enhance
precipitation some on the west facing slopes of the Cascades, so
snowfall amounts could be higher in foothills in eastern Douglas and
Jackson County above 2500 feet.

The models are also in good agreement in beefing up qpf amounts east
of the Cascades, specifically in Modoc County, but also in eastern
Klamath and Lake County later this afternoon into tonight, so the
winter weather advisory has been be expanded to include these areas
as well.

The potential for heavy snow still exist the Mount Shasta region and
western Siskiyou county through this evening. The Winter Storm
Warning for elevations above 3000 feet in this area looks good. Some
of the higher elevations above 4000 feet could see more than a foot
of new snow. Confidence in snow impacting Interstate 5 near Mount
Shasta City through this evening is high, but confidence in the snow
level is a little less certain. Thats because it will be driven
mainly by precipitation rates. If the precipitation is heavy enough,
it could drag the snow level all the way down to Dunsmuir at times.
Generally snow levels should remain around 3000 feet and above, but
could lower down to 1500 feet at times in heavier showers through
this evening affecting portions of the Scott Valley and portions of
highway 96 between Seiad Valley and Happy Camp with the potential
for some road snow accumulations. Confidence is higher for some snow
to accumulate in the Scott Valley, but less near Happy Camp, so
we'll issue a winter weather advisory for the Scott Valley only.
Please see WSWMFR for more details on all the warnings and
advisories.

Moderate to occasionally heavy snow is also possible in the Cascades
around Crater Lake, Diamond Lake and northern highway 97 near
Chemult. The model consensus shows a window moderate to heavy snow
for about a 4-6 hour period late afternoon into this evening, with
precipitation decreasing later tonight as the upper trough swings
through and weak shortwave ridging starts to build in behind it.

We'll catch a one day break Monday with weak upper ridging over the
area. Most, if not the whole day will be dry, then another system
will bring more precipitation Monday evening. Snow levels with this
one will start out higher, therefore snow impacts could be mainly
confined to the higher elevations. -Petrucelli

A pair of low pressure systems well offshore, moving towards the
coast, will dictate much of the weather over the forecast area
through Friday. Deep southerly flow is expected over the region
ahead of the first low Tuesday into Wednesday, and this will result
in moderate to heavy precipitation over Siskiyou County and the
Southern Oregon Coast/Coast Range. Breezy to windy conditions are
possible mainly in the mountains, East Side, and in the Shasta
Valley with 700mb winds reaching values much higher than normal, at
50-70kts by late Tuesday. Strong winds are most likely to surface in
the Shasta Valley Tuesday into Wednesday, so we've issued a High
Wind Watch for this area. The air mass will be warmer than recent
days, so snow levels should be around 5000 feet, so we don't expect
a repeat snowstorm like we're seeing now in Mount Shasta City along
I-5.

The first low will weaken and move north along the coast and away
from the area late Wednesday, and another low will follow a similar
path, weakening and moving to the northeast through the coastal
waters Friday and away from the forecast area Friday night. A break
in precipitation is expected Thursday in between lows, and then
precipitation chances increase again Friday as the next low
approaches. Due to southerly flow ahead of the low, precipitation
will again be focused over Siskiyou County and the Southern Oregon
Coast/Coast Range. Snow levels will again be 5000 feet and higher.
Yet another front arrives Saturday night into Sunday, and models are
in general agreement on the precipitation shield with this front,
affecting much more of the forecast area than the previous few
systems. Snow levels should be much lower with the Sunday system.
-NSK

AVIATION...For the 07/00Z TAFs...Overall, expect widespread MVFR
this afternoon and evening with terrain obscured in periods of
rain/snow, though there can also be periods of VFR. Heavy snow will
bring IFR/LIFR conditions to the Mount Shasta Region. IFR conditions
in fog are possible in inland valleys late tonight into Monday
morning, but timing will depend on when winds decrease and when
higher cloud decks dissipate. This is mostly likely after 12z
Monday. Snow will likely impact KLMT through the late afternoon
hours. VFR conditions are expected in most areas by Monday
afternoon. -Spilde/Keene

MARINE...Updated 245 PM PST Sunday, 6 January 2019...Very steep,
hazardous seas this evening will subside overnight, but remain steep
through Monday. Mainly light west winds tonight will become
southerly ahead of a deep upper level trough and surface low
pressure offshore. This system will slowly approach the area late
Monday into Tuesday, but will stall out just to the west. As a
result, an extended period of south gales and very steep, wind
driven seas are likely beginning Monday evening and continuing
through Wednesday, when the system finally weakens and exits the
region.

Conditions will improve late in the week, but will remain unsettled
through the weekend as several more frontal system make their way
into and through the region. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 9 AM PST Monday for ORZ029>031.
     Winter Weather Advisory until 9 AM PST Monday above 1500 feet in
     the for ORZ023>026.
     Winter Weather Advisory until 9 AM PST Monday for ORZ027-028.

CA...Winter Storm Warning until 10 PM PST this evening above 3000
     feet in the for CAZ080.
     Winter Storm Warning until 10 PM PST this evening above 3000
     feet in the for CAZ082-083.
     Winter Weather Advisory until 10 PM PST this evening for CAZ080.
     High Wind Watch from Tuesday morning through Wednesday morning
     for CAZ081.
     Winter Weather Advisory until 9 AM PST Monday for CAZ085.

Pacific Coastal Waters...Small Craft Advisory for hazardous seas until 4 PM PST Tuesday
     for PZZ350-356-370-376.
     Hazardous Seas Watch from Tuesday afternoon through Wednesday
     afternoon for PZZ350-356.
     Hazardous Seas Warning until 10 PM PST this evening for
     PZZ350-356-370-376.
     Gale Watch from Monday afternoon through Wednesday afternoon for
     PZZ370-376.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
847 PM PST SUN JAN 6 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0846 PM     HEAVY SNOW       MOUNT SHASTA            41.32N 122.31W
01/06/2019  M12.0 INCH       SISKIYOU           CA   TRAINED SPOTTER

            STORM TOTAL SNOWFALL. CONDITIONS ARE ALSO
            VERY FOGGY AND ROADS/SIDEWALKS ARE FROZEN.

&&

BS