An unusual sound was heard Thursday in California — the staccato of raindrops. For the first time in months, rain fell in significant quantities across the parched state. Los Angeles picked up an inch of rain since midnight on Thursday, with higher elevation areas outside the city seeing heavier amounts. Rain also fell in the Bay Area and San Diego, as the first in a series of Pacific storms made landfall.
Heavy rain with embedded thunderstorms is forecast for southern California through Friday, with a second and stronger storm lasting from Friday through Saturday. Heavy snow is forecast for the San Bernardino Mountains as well as parts of the Sierra Nevada, where the snowpack has been running well below average due to a dry and unusually mild season so far.
See also: High and Dry: 10 Devastating Photos of the California Drought
California has experienced record high temperatures and record low amounts of precipitation for much of the winter, a classic recipe for an intensifying drought.
The California wet season typically runs from late November through April 1, but much of the wet season so far has been record dry. For the water year so far, precipitation has been running at just 10 to 30% of the average across southern California, with parts of the state needing at least a foot of rain to alleviate drought conditions.
As of Thursday, 26.2% of the state was classified in the worst category, “exceptional drought”, up from nearly 15% just one week ago. An astonishing 95 percent of the state is experiencing some level of drought conditions.
California had ample water supplies left over from 2012 to endure its driest calendar year on record — 2013. But the state has little, if any, reserves to fall back on if this wet season fails to bring adequate precipitation. State water agencies and federal authorities have announced a series of cutbacks in water deliveries to farmers and municipalities, raising the possibility of an expensive disaster in America’s top agricultural state.
The drought is the most severe one-year drought on record in California, even more severe than the 1976-1977 drought; you have to go back to events that took place before instrument records began in the late 19th century.

With escalating water supply concerns as the dry season rapidly approaches, the discussion from the National Weather Service (NWS) forecast office in Los Angeles on Thursday read like a last-ditch attempt at pulling off a miracle:
Conditions will also be favorable for isolated waterspouts and small tornados Friday into Saturday ... Rainfall amounts with this second storm could be very impressive. There is the potential for 1 to 3 inches for coastal and valley areas and 3 to 6 inches in the foothills and mountains ... with local amounts of up to 8 inches possible along favored south facing slopes.
The NWS did highlight a hazard that comes along with the heavy rainfall. Because of recent wildfires that have broken out in the dry and mild conditions, there is the possibility for flash flooding and landslides in and around the recent burn areas.
California Fire, the main state agency that responds to wildfires, reported on Feb. 19 that it has responded to 600 wildfires since the first of the year, which was a 330% increase in fire activity compared to average.
"Residents located near these burn areas should be alert for the potential of mud and debris flows late Thursday night through Saturday," the NWS said.
Heaviest rain Friday's storm in the #bigsur area. Up to 8" in the high terrain. Flash floods, mudslides possible. pic.twitter.com/ZzV9ftTXYP
— NWSBayArea (@NWSBayArea) February 27, 2014
 
While these storms should make a dent in the state’s precipitation deficit and ensure that the meager mountain snowpack, which translates into California’s summer water supply, is raised to slightly more respectable levels, these storms will not mark an end to the drought. Far from it. In fact, California needs about four to five of these events to have any chance of escaping the drought before the dry season sets in, and long-range forecasts don’t suggest such a scenario is in the cards. (That's not to say it won't happen, just that it is not particularly likely.)
On Feb. 18, the NWS declared that California had just a 1-in-1,000 chance, or 0.1% probability, at eliminating its annual precipitation deficit and having an average wet season.
So the state will take what it can get for now.