The "a" is nothing more than a typo.
It's simply: "there's powder in Aspen"
"Powder" simply means "fresh snow" -- the type that skiers want. It's just a skiing term.
Just google "skiing term powder" for literally 100s of examples,
"Powder: Fresh, dry and lightweight snow that for many is the Holy
Grail of skiing and snowboarding. Large amounts of fresh powder make
for epic skiing conditions."
The "a" is nothing more than a typographical error. It is meant to read "There's powder in Aspen!"
(Note - there is utterly no connection, in any way, whatsoever, between powder snow (i.e., it looks like powder, talcum powder) and the idiom "take a powder".)