2007 Chevy Trailblazer Transmission Slippage

I purchased my Trailblazer SS from a Chevy dealer close to my home (montgomery county, pa) in early September. I noticed today, one of the coldest days of the year, that the transmission would slip between 1 and 2 then again between 2 and 3 during moderated acceleration. The engine noise resembled that of a missed gear change on a manual transmission. I do not have the opportunity to drive the car hard often as I live less that one mile from my place of employment. Today is the first day I have noticed this occurrance. What could the problem be?