WHILE LANDING AT DAWN WITH SNOW & ICE ON THE RWY, THE ACFT DRIFTED LEFT INTO RUNWAY LIGHTS, WHICH WERE BURIED IN A SNOW BERM FROM PREVIOUS PLOWING. THE PLT SAID THERE WAS 16 INCHES OF SNOW ON THE GND & UP TO 2 INCHES ON THE RWY. HE SAID HE THOUGHT HE HAD LANDED ON THE CENTERLINE, LOST CONTROL IN A SNOWDRIFT, THEN THE ACFT DRIFTED INTO SNOW ADJACENT TO THE RWY.