There has been some strong thunderstorm activity nearby the observatory today. While we haven't had any rain, there has been lightning in the area and an impressive display of mammatus clouds.
Here is a close-up of the mammatus clouds:
Thunderstorms can bring dangerous weather here in the back country. It is important for visitors to the area to pay attention to any weather alerts and to do their best to use common sense to try to be safe, especially when there is lightning in the area.
Update: Clouds cleared by sunset and a full night (9.5 hours) of observing was enjoyed by astronomers using the Hale Telescope.