Snow Predictions and South Coast Backroads

Yes, snow is predicted to start Tuesday evening, and some models are indicating that it could be quite the show. Before you plan your trip to the snow, know that ALL the backroads in the South Coast of Big Sur are closed with locked gates. The January rains did significant damage to all our dirt roads (and many paved ones as well) which are still in disrepair, although the USFS has started on drainage and culvert repair on the South Coast Ridge Road. There are locked gates on both the east and west sides of Nacimiento-Fergusson Road. The gate at the summit of Naci and South Coast Ridge Road is gated and locked, as is Plaskett at Highway 1 and Los Burros at Highway 1. The forest has been closed since the storms, but some people are trying to sneak in. Our local law enforcement officer is back, and the closure will be strictly enforced.

Now on to the forecast:

From Daniel Swain of Weather West:

In unusually dramatic fashion, there will be a sudden shift from mild, dry, and quiescent weather conditions essentially statewide for the past 7-10 days to a much colder and more active weather pattern on Tuesday. A very strong cold front (by California standards) will sweep from northwest to southeast across the entire state later on Tuesday, bringing widespread strong and gusty winds and rapidly colder temperatures. Despite its dynamic strength (in terms of the sharpness of temperature and pressure gradients), this initial cold frontal passage will be quite moisture-starved and will only produce patchy light precip (mainly in the form of mountain snow, although a few rain showers are possible at lower elevations). Some spots, however, may remain entirely dry with howling/locally damaging winds and lowering windchills. Winds Tue into Wed will be notably and locally damaging almost statewide with the passage of this (dry-ish) cold front.

The front, however, will be just the beginning of a very active and interesting weather period to come for all of California. Behind the front, very cold air aloft will filter across all of California for the remainder of the week. An unstable airmass, characterized by occasional spokes of vorticity rotating through a very cold offshore trough, will bring periods of convective showers and perhaps isolated thunderstorms statewide. Snow levels will progressively lower with each passing wave of showers from late Tuesday through early Friday. Just how low they will go has been the subject of much social media speculation in recent days, and I’ll discuss that in some detail below.

Rare combination of a very cold airmass aloft plus enough moisture/lift for precipitation = substantial accumulating snowfall below 1,500ft elevation

Per Daniel Swain, everything in the yellow will have snow by Thursday/Friday.


Lastly, and it has generated a lot of buzz on social media, the
chance for snowfall. The highest confidence remains in elevations
greater than 1500 feet seeing snow. While the airmass aloft will
be exceptionally cold, as will most morning temperatures, the
afternoon day time temperatures will still be mostly above
freezing which keeps the skepticism around. What makes
forecasting snow so challenging is not having a firm grasp what
the snow to liquid water ratio (and better known acronym SLR)
will be for system - and of course it rarely stays static through
an event. Higher SLRs result in snow totals in the Santa Lucia`s
over 24 inches between Wednesday and Saturday. Reduce the ratio
and end up seeing a less than 2 percent chance of snow over 12
inches and only a 20 percent chance over 4 inches. For now,
confidence remains in the North and East Bay higher elevations to
receive only light dustings with the Santa Cruz Mountains and the
Santa Lucia range the best chance to receive higher accumulations
that could eclipse the 12 inch mark. This is mainly due to the
strong winds over the ocean that can help release surface fluxes
more readily and allow convective processes to prevail because of
the relationship to the cold air mass aloft. That in addition to
the upslope flow right next to the source of moisture, the ocean.

To recap, this is a dynamic system that will impact the area from
Tuesday afternoon through Saturday morning with multiple hazards.
It is encouraged to enjoy the Monday holiday, but also
recommended to prepare for the upcoming unsettled conditions.