Climate Central: At long last, a series of Pacific storm systems is producing sorely needed rain and mountain snowfall in California, which has been suffering from one of its worst droughts in at least 500 years. The storms, which began Thursday and are forecast to last through the weekend, are likely to have their greatest impact in Central and Northern California, including the agricultural powerhouse region that is the San Joaquin Valley. Parts of Central California may receive as much as 4 inches of rain through...