Perhaps it snowed overnight while you were sleeping?
Light snowfall can easily go unnoticed during the day because, unlike rain, it makes no sound.
I suppose it's also possible for snow to seem to gain weight by compacting slightly if the temperature raises above freezing slightly during the day.
'Ya know how dew is formed on the ground overnight in summer when the temperature drops to the "dew point"? Well, the same thing also happens in winter, except it's referred to as "frost point"...
... Perhaps extra mass is also gained overnight from condensation in the air as the frost-point temperate is reached and air moisture freezes on the existing snow, making it heavier?
It becomes heavier because it compacts as more snow falls and adds weight to it.
You underestimated the amount of extra snow that fell because it snowed overnight or it snowed very lightly and intermittently.
Perhaps it snowed overnight while you were sleeping?
Light snowfall can easily go unnoticed during the day because, unlike rain, it makes no sound.
I suppose it's also possible for snow to seem to gain weight by compacting slightly if the temperature raises above freezing slightly during the day.
'Ya know how dew is formed on the ground overnight in summer when the temperature drops to the "dew point"? Well, the same thing also happens in winter, except it's referred to as "frost point"...
... Perhaps extra mass is also gained overnight from condensation in the air as the frost-point temperate is reached and air moisture freezes on the existing snow, making it heavier?