Eryri weather turns fast, and the summit of Yr Wyddfa is a different world from the car park in the village below. It’s always colder, windier, often wrapped in clouds when the valley is clear. A lot of the call-outs Llanberis Mountain Rescue attend aren’t dramatic; they’re people who got cold, tired, or benighted without the small kit that could have kept a bad afternoon from becoming a serious one. This list splits into “always”…