Winter Storm in Oregon, January 9 to 10, 2024

Area Forecast Discussion
National Weather Service Medford OR
305 PM PST Mon Jan 8 2024

.DISCUSSION...Today into this evening will be relatively quiet with
spotty light precipitation expected into this evening.

A strong cold front will then push towards the coast late Monday
night bringing gusty winds and moderate to heavy rain. Moderate to
heavy precipitation is also expected along the coastal mountains,
western and eastern Douglas County, and the Cascades. Snow levels
Monday night are expected to hover around 5500 feet, therefore road
snow accumulations should be confined to Crater Lake, Diamond Lake
and Lake of the Woods.

The front will push into the area during the day Tuesday bringing
moderate to heavy precipitation, and heavy precipitation for the
coastal mountains and Cascades. Snow levels are expected to start
out around 4500 feet early Tuesday morning, but they will only come
down during the day to around 2500 feet late Tuesday afternoon. As
mentioned heavy precipitation is likely for the Cascades Tuesday
into Wednesday and this could result in snowfall rates exceeding one
inch per hour and possibly as high as 2 inches per hour. With that
said precipitation should not be heavy all the time, and there will
be times where precipitation eases up at times, but it will still be
moderate to heavy. Even so, storm total snow will be measured in
feet along the Cascades and west facing slops near and at the
foothills of the Cascades.

Another impact that was not part of the forecast prior is the
potential for snow near or at the valley floors Tuesday night into
Wednesday morning. There is growing evidence we could get a burst of
precipitation (which could be convective in nature) pushing into the
area late Tuesday evening, followed by a secondary shot late
Tuesday night into early Wednesday morning. Should this pan out this
will result in an enhanced area of precipitation allowing colder air
aloft to get dragged down closer to the valley floors. The net
result could ne accumulating snow in the valleys (similar, but yet
different) from what occured early this past early Saturday morning.
Confidence on snow in the valleys is not has high, but confidence is
higher over the higher passes (Hays Hill, Jacksonville Hill, Camas
Mountain), and the passes on I-5 from Grants Pass to Canyonville.
Because of the above mention reasoning. A winter weather advisory
has been issued to include most of the Rogue, portions of the
Illinois, Including Hays Hill and portions of the Umpqua Basin which
will include the I-5 passes between Grants Pass and Canyonville.
Please see WSWMFR for details on all of the Winter Storm Warnings
and Winter Weather Advisories.

Even though the Cascades will get the brunt of the snowfall, the
Siskiyous are not out of the woods and significant snow
accumulations are expected, including I-5, but storm total snow is
not expected to be as high. Additionally, moderate to strong winds
will be a part of the equation and this could result in near
whiteout conditions at times, especially in exposed areas along and
east of the Cascades. Anyone that plan on traveling during this time
should seriously wait until later in the week when the weather is
expected to be calmer.

Meanwhile, moderate to heavy rain is possible along the coast,
tonight into Tuesday morning and again later Tuesday night into
Wednesday morning. 42 hour storm total precipitation from tonight
into Wednesday afternoon could range from 1.50-1.75 inches north of
Cape Blanco and 2-3 inches along the south Oregon coast.

Another impact from will be moderate to strong winds, along and east
of the Cascades and possibly along the coast tonight and Tuesday
evening, although confidence on this is low and current data suggest
these winds will not be widespread enough to need a warning product,
but we will have to see how the models trend and consider a short
lead time one if things change. -Petrucelli

Overview:

Of note for the long term is the relatively light snowfall amounts
expected across mainly high elevation areas through the weekend, but
on Saturday higher amounts appear more likely and perhaps the most
impactful day in the long term.  Also of note is the potential for
breezy/gusty winds on the east side for both Thursday and Friday.

Further Details:

Starting Thursday, models are indicating a broad long wave trough
across the CONUS, with northwesterly flow over the PacNW. We stay
consistently in this pattern through Friday with good agreement
between the global models. This will bring weak embedded pieces of
energy over the area which will result in light snowfall amounts for
higher elevations. Starting Saturday, we are expecting a change with
the next upper low making its way towards the area. Each of the
deterministic models (GFS, European, and Canadian) have a slightly
different solution/track with the next closed H5 low. This
discrepancy between model solutions brings a lot uncertainty because
the track has significant impacts on where exactly we will see the
highest precipitation and strongest wind speeds. The Canadian is
faster and more progressive through the region; however, the GFS and
European are both slower and each with a slightly different track.
The GFS is farther north as it comes on shore versus the European
which is farther south. Those details will matter for the finer
details, but as of now it looks like either of these solutions will
bring precipitation to the region if they hold. Some of our higher
elevations like the Cascades will likely get snowfall. Depending on
which track wins will determine what kind of wind speeds we will
have to deal with. Additionally, the track will ultimately affect
the moisture fetch and therefore overall snowfall amounts. The
takeaway here is that hazardous travel conditions will be possible
for mainly areas above 5000 feet starting as early as Friday night
and going through Saturday evening.

&&

.AVIATION...08/18Z TAFs...A warm front is bringing some light
precipitation to the region with a mix of MVFR/low end VFR cigs and
MVFR visibilities. Widespread terrain obscurations will persist
through the TAF period. Precipitation will taper off this afternoon
as freezing levels come up. Then a strong front will pass through
the region tonight, bringing increasing winds this evening that will
continue overnight into Tuesday. In addition, low level wind shear
will be a concern for areas west of the Cascades today as well. /BR-y

&&

.MARINE...Updated 215 PM Monday January 8, 2024...Gusty south winds
are persisting north of Cape Blanco. This is bringing areas of very
steep wind driven seas north of the cape with steep swell dominated
seas persisting south of Cape Blanco. Conditions will deteriorate
further later tonight as a strong cold front moves into the region.
This front will bring strong winds with gales expected north of Cape
Blanco and very steep and hazardous seas expected across all areas.
Initially, gales will be from the south, but there will be a quick
wind shift to west late tonight with westerly gales persisting into
early Tuesday morning.

Meanwhile, a very heavy long period swell (16 to 23 ft @ 14 to 15
seconds) will build into the waters by early Tuesday morning. This
heavy swell combined with very steep wind waves will likely lead to
dangerous and chaotic seas Tuesday into Wednesday. Northwest winds
will remain gusty into Wednesday and heavy seas will remain very
high and very steep through at least Wednesday night. Seas will
gradually subside Thursday into the weekend, however, another system
is expected late in the weekend which will bring another round of
building seas and gusty winds. /BR-y

&&

.BEACH HAZARDS...Updated 215 PM Monday January 8, 2024...Active
weather returns to the Oregon Coast this week with a heavy long
period swell arriving by early Tuesday morning. This will bring
dangerously large breaking waves of 23 to 29 ft to the coast and
shorelines of Curry, Coos, and Douglas Counties Tuesday into
Wednesday. All area beaches will be dangerous places to be during
this time as waves inundate beaches and surge into normally dry
areas. Additionally, infrastructure damage and significant beach
erosion can be expected. A High Surf Warning is in effect from 4 am
Tuesday through 10 pm PST Wednesday, and area beaches should be
avoided during this time.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning from 1 AM Tuesday to 4 PM PST Wednesday for
     ORZ029>031.

     High Surf Warning from 4 AM Tuesday to 10 PM PST Wednesday for
     ORZ021-022.

     Winter Storm Warning from 1 AM Tuesday to 4 PM PST Wednesday
     above 2000 feet for ORZ023>026.

     Winter Weather Advisory from 10 PM Tuesday to 9 AM PST Wednesday
     for ORZ023-024-026.

     Winter Storm Warning from 1 AM Tuesday to 4 PM PST Wednesday for
     ORZ027-028.

CA...Winter Storm Warning from 1 AM Tuesday to 4 PM PST Wednesday
     above 2000 feet for CAZ080>083.

     Winter Storm Warning from 1 AM Tuesday to 4 PM PST Wednesday for
     CAZ084-085.

PACIFIC COASTAL WATERS...Small Craft Advisory until 10 PM PST this
     evening for PZZ356-376.

     Hazardous Seas Warning from 10 PM this evening to 4 PM PST
     Wednesday for PZZ356-376.

     Hazardous Seas Warning until 10 PM PST this evening for PZZ350-
     370.

     Hazardous Seas Warning from 1 PM Tuesday to 4 PM PST Wednesday
     for PZZ350-370.

     Gale Warning from 10 PM this evening to 1 PM PST Tuesday for
     PZZ350-370.

&&