1) THE PILOT NOT OBTAINING FORECAST WEATHER FOR HIS ROUTE OF FLIGHT NOR HIS DESTINATION 2) THE PILOT'S INFLIGHT DECISION TO FLY INTO SNOW WITH THE HELICOPTER'S ENGINE AIR INDUCTION PARTICLE SEPARATOR KIT NOT INSTALLED, AS REQUIRED BY THE BELL 206B PILOT'S OPERATING HANDBOOK, AND 3) THE PILOT'S IN FLIGHT DECISION TO TURN THE ENGINE ANTI ICE TO THE OFF POSITION. A FACTOR IN THIS ACCIDENT WAS THE UNSUITABLE TERRAIN THE PILOT WAS FLYING OVER WHEN THE ENGINE LOST POWER. THIS UNSUITABLE TERRAIN CAUSED THE PILOT TO USE COLLECTIVE PITCH TO CLEAR TREES RESULTING IN INSUFFICIENT ROTOR RPM TO CUSHION THE LANDING TOUCHDOWN.