Winter Storm in Oregon, January 6, 2024

Area Forecast Discussion
National Weather Service Medford OR
400 AM PST Sat Jan 6 2024

.DISCUSSION...The next 24 hours will be very active as a winter
storm brings large snow accumulations to the region. This snow and
gusty winds are expected to result in disruptions to daily life.

The storm that is bringing these conditions has already spread
over the coast with a roar. That is, isolated lightning was
observed along the leading edge of the front. Continued
isolated thunderstorm activity is expected throughout the day.
The combination of high surf resulting in dangerous breaking
waves and the possibility of a cloud-to-ground lightning strike
means that S. Oregon beaches will not be a safe place to be at
today.

Further inland, we are expecting snow accumulations of a foot or
more above roughly 4500 feet. Areas between 2500 and 4500 feet are
also expected to accumulate snow, but amounts will vary quite a
bit, so stay tuned to your specific local forecast for amounts.
Accumulations will be highest over the next 4 to 6 hours, and the
rate of snowfall combined with gusty winds will greatly reduce the
visibility, creating very difficult driving conditions on passes
and other mountain roads. Snow loaded trees will also have a
a greater chance of breaking under the moderately gusty winds.
The impact from the snow, wind combination mostly be above 5000
feet from the Cascades west, but will be more widespread east of
the Cascades; see the wind advisory (NPWMFR) for more details for
Lake County.

The storm activity will taper down tonight and showers will become
more scattered around sunset. However, this is also when the
Illinois, Rogue, and Applegate valley snow will be most likely.
The chance a shower moves over these locations is generally
between 40-70% (up a little from yesterdays forecast). It's not a
guarantee that the snow level will be low enough to produce snow,
though. Like the probability of precipitation going up, the chance
for snow also increased, with about 40% of model solutions now
showing conditions for snow at the lowest valley locations (Upqua
Basin not included). Other places in these valleys that are a
little higher in elevation like Ashland, Shady Cove, Jacksonville
Hill have higher chances to see snow closer to 80%.

Gusty west winds will linger east of the Cascades Sunday morning
as will rain/snow showers from the Cascades west. The snow level
is forecast to start around 1800-2200 feet, then rise up to
2300-2600 feet by the afternoon. New snow accumulations on Sunday
should be less than 5" in the Cascades and less than 1" in the
foothills.

A warm front will move through the region on Monday. The spread in
snow level is still quite variable, between 5000 and 6500 feet;
and our forecast leans closer to the higher end of that at 6000
feet. This will limit impacts from snow for all but the roads in
the Cascades. There has also been some questions about the chance
for freezing rain in valleys west of the Cascades Monday morning.
A review of sounding profiles showed the front moving through at
the same time as temperatures warm above freezing in the valleys
(4 AM to 10 AM). There were a small collection of model soundings
that show freezing rain was possible, but that is no more than 5%
of the total grand ensemble the NWS uses. Two places are an
exception to this though. First is in the Klamath River Valley
along highway 96 near the community of Klamath River, where the
chance for freezing rain is around 15%. The second is along Tiller
Highway (highway 227) between trail and Tiller, where the chance
for freezing rain is around 20%. Ice accumulations, if they even
occur, would most likely be no more than 0.05", and should not
lead to more than a localized traffic hazard with no risk to power
infrastructure.

A storm is expected to move through nearly every 24 hours through
this next week. Winter weather and wind related headlines are
expected to be in place frequently through this time. This may
not even be the end of the storm activity either because the
climate prediction center is calling for moderate risk (> 40%
chance) for further heavy rain & snow, and a high risk (> 60%
chance) for much below normal temperatures Jan. 13-19. 2024 is
coming in with a roar!
-Miles

&&

.AVIATION...06/12Z TAFs...A cold front moving through the region
from the northwest is bringing widespread rainfall that will last
through the TAF period, with most of the activity happening this
morning. Low level wind shear is possible as the front passes over,
with winds of 35 to 45 kts from the southwest possible through this
morning.

While activity will decrease into this evening, scattered rain and
snow showers are possible through the TAF period. Showery activity
can locally lower ceilings and visibilities as well as obscure
terrain. -Sven

&&

.MARINE...Updated 200 AM Saturday January 6, 2024...A strong frontal
system is moving through the waters this morning. This will bring
gusty south to southwest winds that will switch to gusty northwest
winds early morning. While sustained wind speeds are not expected to
reach gale force, a few isolated gale gusts are possible, especially
in and near any convective elements within the rain. Isolated
thunderstorms are possible. Very high and very steep, west-
northwesterly seas are expected from Cape Blanco northward tonight
into Saturday. These conditions are expected to result in dangerous
bar crossings as well as high surf along the coast. Seas will
gradually lower late Saturday night into Sunday but will continue to
be high and steep.

Seas will lower further Sunday night into Monday as west-
northwesterly swell diminishes. However, another front (a warm
front) on Monday may bring gusty south winds and areas of steep
seas. Long term guidance shows conditions deteriorating rapidly
Tuesday morning as yet another impactful front moves over the area.
This front will bring a potential for strong, gusty winds followed
by very high seas as large westerly swell builds into the waters.
-Sven

&&

.BEACH HAZARDS...Updated 200 AM Saturday, January 6 2024...Long
period WNW swell will continue to build into the waters with waves
in the 15-19 foot range and wave periods of 16 to 18 seconds. This
will result in dangerous breaking waves in the surf zone of 20 to 24
feet. A High Surf Advisory remains in place through today (please
see the CFWMFR for details). -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 10 PM PST this evening above 2500
     feet for ORZ024>026.

     Winter Weather Advisory until 10 PM PST this evening for
     ORZ029>031.

     High Surf Advisory until 10 PM PST this evening for ORZ021-022.

     Winter Storm Warning until 10 PM PST this evening for ORZ027-
     028.

     Wind Advisory until 4 PM PST this afternoon for ORZ031.

CA...Winter Storm Warning until 10 PM PST this evening above 2500
     feet for CAZ080.

     Winter Weather Advisory until 10 PM PST this evening for
     CAZ081>083.

     Winter Weather Advisory until 10 PM PST this evening for CAZ085.

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 4 PM PST this
     afternoon for PZZ350-356-370-376.

     Small Craft Advisory from 4 PM this afternoon to 10 PM PST
     Sunday for PZZ350-356-370-376.

&&