Complex sentence: On Saturday the 20th of Febuary, the avalanche danger was increased to level 4 due to between 20 and 30 centimetres of fresh snow that fell on the older, established layers.
Split into simpler sentences: On Saturday the 20th of Febuary, the avalanche danger was increased to level 4. Between 20 and 30 centimetres of snow fell on the older, established layers.