Dec. 3 Storm Update: Yes, We Just Got Soaked

Final update, 10:15 a.m. Wednesday (Dec. 3): Just catching up on our December Deluge. Overnight Tuesday into Wednesday, the storm performed as forecast, hitting the North Bay particularly hard. Novato, in northern Marin, got about 4½ inches overnight. But there were rain totals well over an inch throughout the Bay Area. And coming after Tuesday's dousing and a high tide that occurred at the height of the morning commute, the storm led to widespread flooding of highways and viaducts.

Meteorologist Jan Null reported early Wednesday that San Francisco's rainfall since early Tuesday -- 2.97 inches at midmorning and counting -- was the highest two-day total in at least five years.

As we noted last night, the storm was a little slow and a little sparse in bringing rain to the state's biggest reservoirs -- Shasta Lake on the upper Sacramento River system, and Lake Oroville on the Feather River. That changed overnight, with many locations in the Shasta drainage getting close to an inch of rain and sites above Lake Oroville getting close to 2 inches. In context, that's far from a historic rainfall. But it could help the reservoirs begin to make up their drought deficit.

To conclude, for now, here's a Storify pulling together social media reporting on the storm so far:

View the story "Major Storm Brings Heavy Rains to Bay Area" on Storify

Update, 5:15 p.m.: Tuesday: The Bay Area's in the midst of a break from the steady rain that fouled up the morning commute and prompted a flood advisory for the region earlier in the day. But the storm that rolled ashore just after midnight Tuesday morning is not done. Forecasters say that rain will return later this evening and continue much of Wednesday. Mountains in the North Bay and south of Silicon Valley, which have already gotten 2 inches of rain or more, will see another 2 to 3 inches. Lowland areas on the coast and near San Francisco Bay, which have gotten between 1 and 1.8 inches today, could get another inch.

The National Weather Service also says that winds will pick up later Tuesday evening. That raises the possibility that drought-stressed trees now standing in saturated soils could topple.

According to statistics from meteorologist Jan Null, Tuesday has been San Francisco's fourth-rainiest day since early 2009, before the current drought began.

As forecast Monday, the highest rainfall totals Tuesday were recorded far to the south of the Bay Area. Some mountain sites in Santa Barbara, Ventura and Los Angeles counties reported more than 2 inches of rain.

If you're thinking about the impact of the current round of storms on the state's overall drought and water storage picture -- and who isn't -- it's worth mentioning that the areas feeding into California's giant Northern California reservoirs have gotten comparatively modest amounts of rain. Through 4 p.m., less than half an inch of rain had fallen in the Shasta Lake drainage. The highest amounts recorded so far in the watershed above Lake Oroville, which has been rising slowly in the wake of recent storms, are just over half an inch.

Update, 7:55 a.m. Tuesday: This morning's heavy rain has prompted the National Weather Service's regional forecast office in Monterey to issue a flood advisory for the entire Bay Area through 7:30 p.m. Tuesday. This is *not* a warning about a major flood event, but advice that we're likely to see ponding or flooding on roads and in low-lying areas with poor drainage. Also possible: mud and rock slides.

Update, 7:40 a.m. Tuesday: The much-anticipated storm rolled into the Bay Area just after midnight Tuesday morning and has kept up a steady pounding rain for several hours. In the storm's early hours, anyway, the state's heaviest rain totals appeared to be on the San Francisco Peninsula.

As of 7 a.m., rainfall totals from NOAA's California-Nevada River Forecast Center showed Redwood City with 1.29 inches, San Francisco International Airport with 1.17, and "downtown" San Francisco -- actually Mission Dolores the U.S. Mint at Market and Buchanan streets -- with 1.05. St. Mary's College in Moraga, one of the East Bay's consistently rainiest spots, recorded an even 1 inch. Palo Alto has been the rainiest spot in the South Bay so far with .95 of an inch. We'll update totals for the region as the morning goes on.

And yes, the storm is creating problems for both short-distance and long-haul travelers. The California Highway Patrol has reported dozens of traffic incidents in the early part of the morning commute, including a car that somehow managed to crash onto the sidewalk on the west side of the Golden Gate Bridge (that's the side facing the ocean -- the side that's generally closed to pedestrians). The rain and low cloud ceilings have also caused incoming flights into SFO to be delayed by almost four hours, according to the FAA and airport officials.

Update, 4:40 p.m. Monday: Well, the rainy weekend is over and the sun has returned. Next up: a wetter and windier storm that should arrive in the Bay Area Tuesday morning -- and deliver a real deluge to much of Southern California.

The National Weather Service says the storm could bring about an inch and a third of rain to San Jose, 2 inches in San Francisco and 2.5 inches in San Rafael and Santa Rosa by late Wednesday. Forecasters say higher totals will fall in the Santa Cruz Mountains and upland areas of the North Bay. The storm will also feature winds gusting up to 40 mph near the coast and in the region's hills. Isolated thunderstorms are also possible.

Forecasters say the incoming storm will tap into an "atmospheric river," a plume of very moist air, wafting up from the subtropical Pacific. The weather system is expected to hit Southern California dead-on and has prompted the National Weather Service to post a flash flood watch for extensive areas of San Diego, Orange, Riverside, San Bernardino, Los Angeles, Ventura and Kern counties. Watches have also been posted for burn areas near Yosemite and for the area near September's King Fire west of Lake Tahoe.

The National Weather Service says the storm could deliver as much as half an inch of rain an hour Tuesday to mountainous areas of Southern California. The Santa Lucia Mountains, stretching along the Big Sur coast and south, are also expected to get very heavy rain.

The storm is forecast to dump heavy snow throughout the Sierra Nevada, with 2 feet or more expected above 7,000 feet or so.

Over the weekend, hills and mountains south and north of San Francisco Bay saw the most rain, with the highest reported total Monday morning being 4.22 inches on Mount Hamilton. Several locations in the Santa Cruz Mountains and in the hills of the Russian River drainage in Sonoma County got more than 3 inches. Here's the NWS regional rainfall report with three-day storm totals for dozens of locations through Monday morning:

Public Information Statement: 3-Day Rainfall Reports

Original post (Friday, Nov. 28): Admit it: You spend a fair amount of time paying lip service to the drought, or even putting some effort into conserving water. Then when a storm finally interrupts some really nice weather, you're all, "Man, I wish it wasn't raining."

Well, prepare to have whatever your outdoor plans were for this weekend interrupted. Because the most significant rainstorm in the Bay Area this season is now approaching Northern California.

The National Weather Service says rain will hit Sonoma and Napa counties later today and spread to the rest of the region Saturday. The storm will be moderate to heavy, and is the first in a series of "rain events," as the NWS puts it, over the next five-six days.

Motorists are cautioned to slow down, as driving could be difficult this weekend and through the middle of next week.

Diana Henderson, NWS forecaster for the San Francisco Bay Area/Monterey, said the precipitation will occur on and off through most of next week, and that we should see a decent downpour.

"It's definitely the strongest one we've had so far," she said. "And, we'll have the heavier precipitation."

Henderson said the NWS expects gusty winds sometime around Wednesday. Those high winds and the most rain are expected mainly in high-elevation spots like Mount Tamalpais and Mount Diablo, as well as the Santa Cruz Mountains.

The upcoming storm will have slightly more impact on the drought than the smaller ones that hit the region in recent weeks, Henderson said.

Eighty percent of California is experiencing "extreme drought," and in the better part of the state, drought conditions are designated as "exceptional," the driest level on the drought scale.