Winter Weather in Oregon, December 14, 2020

Area Forecast Discussion
National Weather Service Medford OR
902 AM PST Mon Dec 14 2020

.DISCUSSION...No updates are needed for this morning. There will
be a brief break in the weather today as a period of shortwave
ridging moves through the area. Isolated showers continue along
the coast and north of the Umpqua Divide this morning, but this
activity is expected to wane as we head into the afternoon hours
today. Despite widespread cloud cover west of the Cascades, most
areas will see some sunshine today. This break in the weather will
be shortlived, however, as the next front in the active pattern
moves into the area late tonight into Tuesday morning. For more
details on this, see the previous discussion below. /BR-y

&&

.AVIATION...For the 14/12Z TAFs... Just a few showers persist this
morning as the low moves through the region.  There are pockets of
MVFR ceilings and obscured terrain over most of southern Oregon.
It's hard to tell how much there is because of a large VFR cloud
deck overhead this morning.  For the most part VFR will prevail for
the majority of the TAF sites this morning. There are hints at some
isolated fog and low level stratus in some of the valleys this
morning.  So there is a low probability some of that forms over some
of the TAF sites.  However, the air mass seems rather unstable a few
hundred feet above the surface, so the probability of fog forming is
quite low.

Otherwise, VFR will prevail shortly after sunrise with VFR cloud
ceilings.

-Smith

&&

.MARINE...Updated 850 AM PST Monday 14 Dec 2020...Seas are
expected to remain high and very steep this morning, with large
breaking seas and hazardous bar conditions. Seas will lower later
this afternoon, but remain hazardous to small craft through Monday
night.

South winds will increase ahead of the next front tonight into
Tuesday and will be followed by another very high and very steep
long-period westerly swell of around 20 feet Tuesday into Wednesday
morning. We upgraded the hazardous seas watch as we fell confident
seas will reach and exceed 18 feet Tuesday night.

Yet another strong front will move in Wednesday followed by another
very high swell Wednesday night into Thursday.   This swell group
looks like it will be lower compared to the one moving through
Tuesday.  Right now guidance is suggest wave heights around 14 to 18
feet.

Even though there may be a brief break late this week, it won't stop
there as models show another strong front arriving next weekend.

-Sven

&&

.PREV DISCUSSION... /Issued 342 AM PST Mon Dec 14 2020/

DISCUSSION...Showers are on the decrease across the forecast area with
snow levels hovering in the 3500 to 4000 foot range. Temperatures
have been mostly steady this evening across the area at the
surface, but they continue to cool aloft. Some holes opening in
the overcast along and near the coast and to the lee of the Marble
Mountains and Siskiyous under a general flow from the west-
northwest will get wider and expand across the area allowing for 5
to 15 degrees of cooling overnight through the morning.

With roads being wet in many areas and temperatures cooling,
expect that some icy spots are likely to form, especially in areas
with snow around. Fog and low clouds are possible, but a recent
look at the atmospheric profile indicates that fog is unlikely to
be widespread at the surface due to lingering instability from
the continuing cold air advection through sunrise.

A brief period of ridging today should stabilize the region
enough for patchy, to localized areas, of fog to develop tonight
into Tuesday morning. Most west side valleys, aside from Scott and
Shasta valley of Siskiyou county where freezing fog is possible,
are expected to remain just above freezing. Freezing fog is also
possible in the Klamath basin and north in the low laying areas on
the east side of the Cascades along route 97.

The front on Tuesday continues to trend weaker once it interacts
with the coast as QPF and snow amounts decreased slightly again
with this mornings update. A challenge with this front is that at
the heaviest expected snowfall, snow levels will be rising from
4,000 feet before noon to about 5,500-6,000 feet by late afternoon.
This will lead to more mixed phase precipitation and rain by
evening, increasing the potential for ice concerns with refreezing
overnight. Snow amounts on Cascade roads, like route 140, 230,
and 138, are likely between 0.5" and 1.5", before switching over
to mixed phase and liquid precipitation later. Snow should be
fairly wet and heavy, coming down in a fairly condensed timeframe
creating its own driving hazard, before the possibility of ice
later.

While the Tuesday front trended weaker the Wednesday evening
system has trended stronger. Snow amounts in the Cascades are now
nearing watch/warning criteria. Amounts range between 12" and
22". Amounts in the Siskiyous are still nearer to advisory levels,
but a change to how quickly the leading warm air mixes out or an
increase in total QPF will quickly tip the snow amounts to warning
levels. Snow amounts across the east side are generally just
under advisory criteria. However, amounts in the Warners are near
advisory criteria and with the last two systems, QPF was
underestimated until the 36-48 hour time range. There seems like a
good chance this will happen again, so anticipate amounts
increasing here with later updates. Expect strong winds with the
front and for them to remain elevated through Thursday.

Further unsettled weather is expected next weekend after what
should be a relatively calm Friday, aside from some possible
fog/freezing fog in the morning. -Miles

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory until 4 PM PST this afternoon for ORZ021-022.

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 4 PM PST Tuesday for PZZ350-356-376.
     Hazardous Seas Warning from 4 PM Tuesday to 10 AM PST Wednesday
     for PZZ350-356.
     Hazardous Seas Warning until 10 AM PST this morning for
     PZZ350-370-376.
     Small Craft Advisory until 4 AM PST Tuesday for PZZ370.
     Hazardous Seas Warning from 4 AM Tuesday to 10 AM PST Wednesday
     for PZZ370-376.

MNF/MB/CZS

PRELIMINARY LOCAL STORM REPORT
National Weather Service Medford OR
516 AM PST MON DEC 14 2020

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

0513 AM     HEAVY RAIN       SSW GOLD BEACH          42.41N 124.42W
12/14/2020  M1.00 INCH       Curry              OR   TRAINED SPOTTER

            24HR TOTAL FROM 5AM TO 5AM PST. HEAVIEST RAIN OVERNIGHT.

&&

MBLISS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MEDFORD OR
802 AM PST MON DEC 14 2020

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

0801 AM     HEAVY RAIN       6 E GOLD BEACH          42.42N 124.31W
12/14/2020  M1.35 INCH       CURRY              OR   TRAINED SPOTTER

&&

SBN