What does the latest atmospheric river storm mean for Paso Robles Wine Country's rain year?

[Editor's note 1/10: I've posted a quick summary of the flooding and other impacts of our January 9th atmospheric river storm in a comment. We're posting regular updates on our Twitter, Facebook, and Instagram pages. And I'm planning a blog with a more comprehensive report next week.]

Our current atmospheric river storm, which isn't even over yet, has received a lot of press with even big east coast papers like the New York Times and Washington Post giving it front-page coverage. The San Francisco Chronicle is dedicating most of its homepage to stories about the storm and its impacts. Down here in Paso Robles we got 3.53" of rain yesterday and last night, and have received another quarter-inch of rain in showers this afternoon. With other storms just a day or two out, I thought I'd do a quick assessment of what the impacts of the rain have been so far and what we're expecting next.

The tl;dr for those of you who start meals by eating dessert: the impacts to this point have been essentially all positive for us. We've already surpassed our rainfall for the winters of 2019-20, 2020-21, and 2021-22. The ground is saturated, but we haven't seen either flooding or noteworthy erosion. And Las Tablas Creek is flowing for the first time since early 2019:

During a break in the storm Viticulturist Jordan Lonborg got down to shoot this video of Las Tablas Creek… and it’s moving fast, has filled up our reservoir and is now flowing through the spillway for the first time since early 2019! pic.twitter.com/mTWzT1o9hJ

— Tablas Creek (@TablasCreek) January 5, 2023

We're at just about 200% of our expected January 5th total for the rainfall year which started in July. Looking month by month, we more than tripled our normal December rain and finished just a fraction of an inch behind 2004 for our wettest December ever. And unlike last year, when we had a wet December and then an almost totally dry spring, it looks like we'll surpass our normal January rainfall this weekend. Here's what it looks like so far (January's total is through this afternoon, while the expected total is for the entire month):

For the rainfall year, we're up to 19.6" of total rain, with more than half the rainfall season to go. That's terrific. The fact that Las Tablas Creek is flowing is a great sign of the saturation of the soils; there are several irrigation ponds upstream from us, and other than some surface runoff that happens during storms, it's not until those ponds fill up and the top several feet of soil is saturated that the creek flows continuously. Today, the creek is flowing merrily into our lake:

In the vineyard, you can practically hear the cover crops growing. Although we move the sheep out of the vineyard during rain events (both to provide them shelter and to keep the soil compaction that they cause in very wet weather to a minimum) there will be ample grass whenever it dries out enough to let them back in:

You can get a sense of how excited they are by all this grass from the video we shared Tuesday on Twitter:

Our sheep are experiencing a couple days respite from the rain. They spend the rainy days under shelter, but we moved them out yesterday and on to fresh pasture where they are enjoying the results of a productive rainy season. pic.twitter.com/asV0SGaKVr

— Tablas Creek (@TablasCreek) January 3, 2023

Most people who haven't spent a winter in the Paso Robles area think of it as a desert climate. And it is, in the summer. But the six winter months are wet enough on average, at least in the western fringes of the AVA where we're located, to qualify as a temperate rain forest if those months were extrapolated year-round. That fact, combined with the hilly topography, means that we're pretty well set up for heavy rainfall events. You can get some localized stream flooding (though Las Tablas Creek hasn't flooded in the two decades that I've been out here). You can get some minor mudslides where the roads have been cut through the hills. And you can have downed trees from wind and wet soils that can knock out power. But our calcareous soils are exceptionally porous, which means that they transport massive volumes of water from the surface to deeper layers before they reach saturation. By the time they do saturate, the winter grasses tend to be well-enough established that erosion is minimal (as evidence, check out my photo essay from January 2017 after we'd broken our record for our wettest month ever). Finally, the hilly landscape means that the extra water by and large flows off and fills up our reservoirs rather than flooding our towns. Lake Nacimiento, into which Las Tablas Creek and the rest of our watershed empties, was up to 747.7 feet as of today, 32 feet higher than it was just over a month ago on December 1st, but despite the billions (yes, with a "b") of additional stored gallons of water, the reservoir is still at just 38% of its capacity. Lake San Antonio is at just 13% of its capacity. We can get a lot more rain before we have to start worrying about where it might go.

Looking forward, we're expecting another major Pacific storm Sunday into Monday. And it seems like there's another one lined up behind that later next week. But while we'll be watching the forecast we're not expecting the potentially dangerous impacts for which northern California is preparing. Some of that is because it seems like these storms will be aimed such that the largest precipitation totals will be a little north of us. But just as much, it's because our soils and topography are uniquely well suited to dealing with large amounts of water in a short time. After all, we got more than a dozen inches of rain in a single storm in January 2021, and the impacts were almost all positive.

So while I'll be checking our weather station's totals regularly it won't be with dread. The opposite, really. After consecutive drought-reduced crops (see my recaps for 2021 and 2022 if you want the gory details) I'm hoping for a historically wet winter: something that will replenish our aquifers and reservoirs, delay budbreak to a more normal time frame, and set us up for a couple of years. This has happened before, in winters like 2004-05, 2009-10, and 2016-17. And it feels like we're well on our way to a similar result this year. Let's keep it coming.