You may find this website useful for current and predicted weather conditions, both for Castilia-Leon and Asturias. There are specific pages to provide information on mountain areas etc though you may need to rummage about a bit. And do remember this is Spring - todays snow could be gone tomorrow, and tomorrows sun could be under three feet of snow by Sunday.
http://www.aemet.es/en/eltiempo
I've walked the Salvador in Spring and it was beautiful, and cold, and wet. But that was then, it will never be quite the same again. Go. And if the weather gods decide to play hardball, catch a bus