Experiencing its driest year on record, large parts of California need well over 15 inches of rain to emerge from severe drought.  A vigorous storm crashing into its central coast Friday will supply some much-needed rain, but perhaps too much at once.  Forecasters warn strong winds, flash flooding, mud and debris flows, and even a few weak tornadoes may accompany the powerhouse weather system.

The incoming storm may be the largest rain event in Southern California since March 2011 says the National Weather Service.

It is actually the second in a series of two.  On Wednesday, a weaker system dropped roughly 0.5-2 inches over a sizable section of the state.  Round two arrives tonight into the weekend, and could drop several inches of rain in Southern California, explains the National Weather Service office serving Los Angeles:

Storm #2 is still on track to bring a potent punch of rain, snow and wind to the area. Rain will develop across the Central Coast this evening and will spread south and east tonight and Friday morning with widespread shower activity expected to continue from Friday afternoon through Saturday night. Rainfall totals will be quite impressive, ranging from 1-3 inches across the coasts and valley to 3-6 inches in the foothills and mountains. Locally higher amounts will be possible in favored upslope areas.

The intense storm will be energized by jet stream (high altitude) winds of around 150 mph.

“Look for heavy rain…very strong winds…thunderstorms…as well as a risk for waterspouts and weak tornadoes to develop under this jet,” the National Weather Service warns.

Tornadoes are not terribly uncommon in California in winter. USTornadoes.com reports 55 tornadoes touched down in California in February between 1950-2011, making it the second busiest month for twisters. March is the most tornado prone month, with 69 touchdowns in the 1950-2011 record.

The NWS also expressed concerns about rainfall rates, which could reach 1 to 2 inches per hour for a time Friday:

Communities in and around recent wildfires, especially the Colby, Madison, Powerhouse, Madre, and Springs burn areas, will need to be alert for heavy and intense rainfall which could produce flash flooding with mud and debris flows. Drainage areas should be cleared of debris to help reduce the chance of urban flooding.

In the mountains, winter storm conditions are expected, with 1-3 feet of snow forecast at elevations above 7,000 feet.  This is surely  a good thing given the state of California’s snow pack – less than 50 percent of normal year-to-date.

Farther north, some beneficial snow fell Wednesday and Wednesday night, with 6-12 inches in the Lake Tahoe region.

State of the drought

As of Wednesday, 95 percent of California was experiencing drought conditions – roughly the same as the week prior.  However, over the past week, the area designated in extreme to exceptional drought increased from 68 to 74 percent.

“Benefits of California’s early-February precipitation are being overcome by resurgent warmth and dryness, leading to rapid expansion of extreme to exceptional drought  into the San Joaquin Valley and the southern Sierra Nevada,” writes the U.S. Drought Monitor. “By February 26, the California Department of Water Resources reported that the Sierra Nevada snowpack contained an average of 5 inches of liquid, just 22 percent of the late-February normal.”

The drought has elevated the state’s fire danger, depleted reservoir levels, and adversely affected agriculture.

“The dry conditions have necessitated out-of-season irrigation or abandonment of orchards or permanent crops,” reports Drought.gov.

The NWS Climate Prediction Center forecasts the drought in California to persist or intensify over the next 90 days.

Video: Rain washes over drought-stricken California