What weight is your snowflake? Looks like it comes in DK or Chunky. Since you have the yarn, knit a sample on about 20 sts and see if you get close to the gauge for the pattern which is 3 sts per inch, and if that's too loose or too tight a knit. That's the main criteria for subbing one yarn for another - will it knit up right for the pattern.
sue- knitting heretic