United States

By Alex Sosnowski, Expert Senior Meteorologist

December 15, 2014; 4:11 AM ET

Share |

As the train of storms from the Pacific continues, the latest dose of heavy rain from Dec. 11 and 12, 2014, has helped significantly with California and regional drought relief.

A general 3-6 inches of rain fell on northern California with 1-3 inches projected to fall along much of the coast of Southern California with lower amounts farther inland.

This translates to between 17 and 100 million gallons per square mile from this storm alone.

Locally higher amounts ranging from 7 to 14 inches of rain have fallen on parts of northern California from the Thursday and Friday storm. The greatest rainfall, 14.80 inches occurred in Shasta County, in the southern Cascade Range, in California.

According to Western Weather Expert Ken Clark, "More rain has fallen this past week than most places had for the entire winter last year."

Significant rainfall occurred in the heavy agricultural areas of the Sacramento and San Joaquin valleys with between 2-3 inches and 1-2 inches respectively from the late-week storm.

RELATED:
Biggest Storm in Years for California to Cause Flooding, Mudslides
Western Weather Expert Blog by Ken Clark
Interactive California Radar

Runoff from the storm caused water levels to surge rapidly in streams and will eventually begin to empty into lakes and reservoirs. The storm from early in the month sent water flowing through Yosemite Falls.

Shrinking water levels in lakes and rivers throughout the state have created visual evidence of the drought conditions as seen at Folsom Lake, about 40 miles from Sacramento.

(Photo/California Department of Water Resources)

(Photo/California Department of Water Resources)

A couple of additional soaking storms are forecast for next week, before the wet pattern shifts northward later in the month.

Much of California and portions of neighboring states have been in the throes of extreme to exceptional drought from this summer into this fall.

The drought has its roots to a couple of years ago, when storm systems with rain and mountain snow became scarce.

The map shows the drought status as of Wed., Dec. 10, 2014.

During the last part of November 2014, storms with soaking rain returned to the region.

From Dec. 1, 2012, to Nov. 29, 2014, San Francisco racked up a deficit of 20.9 inches, which was about 50 percent of its normal average rainfall. Since Nov. 29, the city has received more than 8 inches of rain, which is nearly six times that of average for the two-week period. This has cut the approximate two-year deficit by about a third.

In the last two years, Los Angeles incurred a rainfall deficit of 14.9 inches, which was about 44 percent of its normal average rainfall. Since the end of November, the city has received nearly 3 inches of rain, which is close to four times that of average for the two-week period. The recent rainfall has reduced the two-year deficit by about 20 percent.

Up to several feet of snow has fallen prior to this week's storm in the high country of the northern Sierra Nevada and southern Cascades. Yards of snow will fall over the higher terrain of these mountain ranges through next week, which will be water in the bank for this coming spring and summer as it melts and flows into area streams and viaducts.

While the past and future rain during December will help the drought situation in the short term, additional rain will be needed through this winter to completely erase the rainfall deficit and long-term drought.