Snow layers (stacked in any amount) placed by the player or spawner from weather will occasionally disappear when loading a game file, leaving one or two layers in its place. 

From the testing I have done, this only occurs to snow layers that are exposed by the sky. If the sky is obstructed by another block, then the amount of layers the player puts down will remain.

It appears this does not affect taiga biomes (even at high altitudes where snow can spawn), but does effect snowy taiga, snowy beaches, snowy plains, and frozen oceans. I have not tested other cold biomes. 

This only occurs when loading the game file. Traveling between dimensions or loading in chunks don't appear to affect this.

Most cases occur during another bug where the weather is clear but the clouds appear dark as if there is a thunderstorm, but not limited to this, may happen without this secondary bug.

In some cases, I have observed only a specific biome's snow layers being reset, while the biome adjacent and loaded in the same chunk will remain with the stacked layers placed by the player. There have also been times where random groups of layers will be reset. 

This only effects snow layers, snow blocks remain unaffected.

Any blocks that did not have a snow layer on it, will have one or two layers upon reloading the game file if the bug activates.