https://www.mercurynews.com/2019/02/13/in-sierra-nevada-a-roofalanche-warning-issued-as-rain-falls-on-snow/

As a powerful atmospheric river storm crashes into the Sierra Nevada, which has been blanketed with several feet of new snow in recent weeks, meteorologists with the National Weather Service in Reno issued a warning Wednesday for potentially deadly ‘roofalanches,’ the sudden release of snow from rooftops.

The weather service in Reno said that heavy rain is possible below 7,000 feet Wednesday. With several feet of snow on roofs throughout the Sierra Nevada, rainfall “will make snow on roofs more susceptible to rapidly sliding off roofs,” according to the weather service.