Bay Area on snow watch: Some snow possible to near sea level on Monday morning

  San Ramon Hills @ 8am Monday: Our puppy Riley investigates snow.

There aren't many weather patterns that can bring snow to near sea-level around the Bay Area, but its looking like we'll see precisely that to start the week.

A very cold airmass is dropping down the coast, with air cold enough to support snow levels approaching 500 feet in the North Bay and down to 1,500 feet around San Jose and the southern end of the Bay Area.

There are a couple things working for this system to drop low snow:  1) obviously the source of the cold air: dropping down out of Canada from north to south mainly over land (that offers little modification versus our typical pattern that brings in moisture off the more mild Pacific ocean), 2) the time of day the best dynamics with this system kick in - during the early morning hours of Monday until midday coinciding with the coolest time of day.

If the system tracks more over the coast/ocean, we may end up seeing slightly heavier rainfall totals .33" to 1.5" in spots vs. the .10 to .50" expected with the chilly, relatively drier air.

The NWS office in Sacramento issued a Winter Storm Warning for the Central Valley due to anticipated accumulations to near 3" in places that would make for a challenging morning commute in many areas should the snow totals verify. 

The Bay Area being closer to the ocean and the water of the inner bay region will see slightly more mild air at the surface that may limit accumulating snowfall closer to water.  However, inland valley locations like the TriValley, Napa Valley and southern end of the Santa Clara Valley will be far enough away from this marine influence to see a better chance for some snow mixed with rain at times, especially under heavier or convective showers that could drop a dose of "thundersnow" - that is thunder mixed with snowfall.

Those who use mountain drives and hilltop commutes like Hwy 17 (summit near 1,700 ft.) will need to closely monitor road conditions Monday through the afternoon.  Again on Tuesday morning, road conditions could be tough not from snow but rather a chance of icy conditions as snowmelt and rain from the day before freeze overnight.  Lows Tuesday morning Bay Arew wide will likely be in the 20s inland, with mid 30s closer to the inner Bay where Bay water temps should keep things a tad more mild.

The folks @ Mavericks Surf had been closely monitoring a decent long-period swell reaching the coastline beginning Tuesday.  Wave heights are not expected to be as high as previously thought, and the ongoing breezy and on/off rainy conditions prompted organizers to pass on this opportunity this week.

The second half of the week should will bring in a series of weather system undercutting a ridge of high pressure to our northwest.  The Thursday system appears to be pulling in remnant moisture from former Typhoon Nida, that could bring in locally heavy rains especially in orographically enhanced regions like the Santa Cruz and North Bay mountains.  Temps should slowly moderate through the week, that will yield rising snow levels but low enough to pump up some solid snow totals in the Sierra.

Snow levels will likely range from 500-1,500 on Monday to near 3,000 feet on Wednesday to 4-5,000 feet by Thursday.

For More Information:

CalTrans Roadway Information, National Weather Service Monterey