11:04pm UPDATE from Dave Hovde:
A blizzard warning was added for Santa Barbara County mountains from 4a Friday to 4pm Saturday
Winter Weather Advisories were added for much of the area not covered in other advisories until 1p Thursday. 2-4" of snow is possible with winds to 45mph.
So snow is looking likely now for any elevation above 2000ft, and possibly as low as 1000ft.
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It seems like we've been talking about the storm for weeks now and it is finally here. As expected, the first impact came from the strong NW Winds. Winds have already hit 50+mph for parts of the Central Coast and wind advisories are in place into early Wednesday for the winds which can gust to 55mph, and up to 65 or 70mph in the SW portion of Santa Barbara County where a high wind warning is in place into Wednesday morning. Even after this advisory/warning window drops it will still be quite breezy to windy thru Wednesday.
Scattered showers (rain/mix/snow) are possible at any time but the activity will increase on Wednesday. At first, the activity is very on and off but by Thursday into Friday, rainfall will become more widespread with thunderstorms possible due to the cold nature of this system. Highs for the next few days will struggle to hit the lower 50s and some places will not even get that warm.
This is all due to the upper air pattern which has backed a huge trough from the U.S. West out toward the Pacific. This will allow air from the Canadian plains to enter California. This trough is also a powerful jetstream that will spin up instability as it lingers over California into the weekend.
This is a pretty rare system for the Central Coast. While snow is somewhat common in the Santa Barbara high country each winter season, it is far less common in SLO county. And snow levels of 1000-2000ft are very rare. There were some significant snow events in the late 80s which delivered snow to the Southern Salinas River Valley floor but other than that we've seen more flurry events than accumulating snow events.
My forecast aligns with the National Weather Service of 1-6" of snow down to about 2000ft. I think the actual snow level goes lower than that but the question then becomes temperature and if snow could accumulate or just melt when it lands. The lows from the northern Cuesta Grade into Paso Robles are right around freezing so any kind of accumulating snow is a tough call. But by 2000ft this looks a lot more likely. Regardless there are winter storm warnings and a winter weather advisory in place for those interior and higher elevation locations, and those advisories go Saturday.
Yesterday it looked like Saturday the first system would kick out but it looks more like Sunday now with only a brief break before another system later Monday into Tuesday. There are also a series of other systems possible into and thru the first week of March as well. Please examine the graphics for some potential dates. This is a longer-term outlook so the timing and intensity of all of this could change a great deal.
Additionally, waves will be huge for the next day or so with max sets to 20ft possible for the west-facing Central Coast and 11ft in the channel. Advisories for high surf are also in place.
I should mention that rainfall rates will range from 0.50-1.0" per hour near the main frontal band on Friday bringing a threat of urban flooding and issues near recent burn scars.
The precipitation totals for the majority of the south Santa Barbara coast will be 1-3" and could be more than that.
For the Central Coast, the rainfall should be a little less in the .50-1.5" range.
Grapevine travel could get dangerous Friday into Saturday with some significant snow potential there. Above 4k feet, we could start to see feet of snow accumulating with this more powerful part of the storm Friday.
Saturday could also be convective, in other words: t-storms (waterspouts or small tornadoes), rain, hail, and brief heavy showers. Snow levels will be higher at about 3k feet but that is still pretty low.