THE PILOT DID NOT OBTAIN A WEATHER BRIEFING PRIOR TO THIS CROSS COUNTRY FLIGHT. THE WEATHER INFORMATION AVAILABLE ESTABLISHED THAT COASTAL STRATUS CLOUDS WITH ACCOMPANYING COASTAL HILL MOUNTAIN OBSCUREMENT WAS FORECAST. ACCORDING TO THE OFFICIAL WEATHER REPORTS AND WITNESS OBSERVATIONS, THE ACCIDENT SITE WAS OBSCURED IN CLOUDS AT THE TIME OF THE CRASH. THE ACCIDENT SITE IS AT THE END OF A LONG NARROW VALLEY NEAR THE TOP OF A RIDGE LINE. AT DEPARTURE FROM HAYWARD, THE PILOT ORIGINALLY ASKED FOR A STRAIGHT OUT DEPARTURE, WHICH THE LOCAL CONTROLLER DENIED DUE TO A NOISE ABATEMENT PROCEDURE. THE PILOT THEN ACCEPTED A RIGHT CROSS WIND DEPARTURE. THE ENTERANCE TO THE NARROW VALLEY IS IN CLOSE PROXIMITY TO A RIGHT CROSS WIND DEPARTURE PATH. AT THE TIME OF THE AIRCRAFT'S DEPARTURE, THE AIRPORT WEATHER CONDITIONS WERE CEILING 1,000 FEET, VISIBILITY 10 MILES. SIX MINUTES AFTER THE FLIGHT DEPARTED, THE AIRPORT WENT IFR WITH A 900 FOOT CEILING.