(KTXL) — Heavy snowfall has been falling throughout much of Northern California this winter and as another atmospheric river approaches, but some residents welcome the ‘sierra cement,’ a certain type of snow that may form as rain falls on top of freshly-fallen snow.
Sierra cement, a nickname for this type of snowpack, is when the snow on the ground and on roofs goes from light, fluffy snow to a harder and more sturdy snowpack.
Inside the light, fluffy snow, holes and openings will begin to form, and if rain falls within a few days, it will get into those holes causing the snow and rain mixture to freeze into a hard cement-like material.
Once the snowpack hardens from the rain, it becomes much heavier making it harder to clear and can cause structural damage.
After being hit with two winter storms that brought several feet of freshly-fallen snow to the Sierra Nevada, an atmospheric river described as being “warmer” is expected to hit the same area over the weekend, creating the perfect situation for sierra cement.
Officials across the Lake Tahoe area and the greater Sierra Nevada are advising residents and businesses to clear snow from their roofs ahead of the storms.
Many rooftops are covered in several inches or even several feet of snow. The expected rain can cause the snow on the rooftops to harden before falling off, which could lead to a roof collapse if enough of it gathers.