Smoke over Yosemite and the foothills is likely from the Aspen Wildfire in the Sierra National Forest, near Huntington Lake.
http://inciweb.org/incident/3552/
Quote
NWS Hanford
AS THE HIGH NUDGES EAST IT HAS OPENED THE DOOR TO MORE MONSOONAL
MOISTURE TO MOVE NORTHWARD INTO THE REGION. WE HAVE HAD A FEW
THUNDERSTORMS DEVELOP THIS AFTERNOON OVER THE HIGHER ELEVATIONS OF
THE SIERRA NEVADA. AN EASTERLY WAVE MOVING ACROSS SOUTHERN ARIZONA
ALONG WITH A SOUTHERLY FLOW IN THE MID LEVELS WILL AID IN
BRINGING THE MOISTURE NORTHWARD LATE TONIGHT AND FRIDAY WHICH WILL
BRING A BETTER CHANCE OF THUNDERSTORMS FOR FRIDAY AFTERNOON.