SAN FRANCISCO (CBS SF) -- As extreme drought conditions continue to expand across the San Francisco Bay Area, a leading climate researcher issued a new warning Thursday of another sign that a water supply crisis is developing across the region.Dan McEvoy, a researcher with the Western Region Climate Center, told KPIX 5 he was startled to discover that several locations in Sierra had seen the biggest decline in snowpack's water content on record for the time span covering the first three weeks of April.At several key reporting locations across the Sierra range, the water content being stored...…SAN FRANCISCO (CBS SF) -- As extreme drought conditions continue to expand across the San Francisco Bay Area, a leading climate researcher issued a new warning Thursday of another sign that a water supply crisis is developing across the region.Dan McEvoy, a researcher with the Western Region Climate Center, told KPIX 5 he was startled to discover that several locations in Sierra had seen the biggest decline in snowpack's water content on record for the time span covering the first three weeks of April.At several key reporting locations across the Sierra range, the water content being stored...WW…