Snow layers exposed to the sky incorrectly regenerate in chunks in snowy biomes

When logging on to a world, snow layers reset back to the first layer and sometimes completely disappear on previously loaded chunks.It also affects when the chunk is reloaded without the need to leave the world.

Analysis

• Weather and issue was introduced in Minecraft in version 0.12.1 alpha build 1

• The issue was fixed exclusively for snow blocks in version 0.17.0.1 (MCPE-11867), but persists for snow layers

Steps to Reproduce:

1. Create a new world with the seed 475
2. Type /weather rain
3. Wait for the snow layers to pile up
4. Reload the world

Observed Results:
Most of the snow layers reset back to the first layer, or sometimes disappear completely.

Expected Results:
Snow layers should not reset back to the first layer or disappear when reloading the world or reload chunk.