First winter-like storm of the season for CA

A system is currently taking shape in the Eastern Pacific that will intensify as it approaches the coast tomorrow. A good moisture tap exists with an old Central Pacific tropical depression, and baroclinic instability will allow the system to spin up pretty quickly before moving ashore in NorCal tomorrow afternoon. Rain will develop with possibly a few embedded thunderstorms, though winds associated with this rain event will not be too impressive. The cold upper low will slide SE across the state on Friday, generating some showers and possible thunderstorms in the conditionally unstable airmass behind the main front. Rainfall of 1-2.5 inches is likely in the Bay Area, 0.75-1.5 inches  in the Central Valley, far North Coast, and most of SoCal. Mountain areas could see 1.5-3.5 inches of liquid equivalent, though all of this will be in the form of snow (snow levels drop to 3000 feet by Friday in the north). The ski season in the Sierras will really get going by later this weekend–there is currently no snow at all at the 8,000 foot level! This will be a very beneficial event for the state, outside of the potential for mudslides and debris flows near the recent wildfire burn areas in SoCal. Tstorm potential looks moderate at this time…with the outside chance of a severe storm in the Valley. Long term: no big storms on the horizon, for some cold northerly flow and possibly some unsettled weather are in the offing…