Interview Dillema - Advice Needed

I was hoping some of you could give me avice based on your experiences. Here's the situation:

I'm a recent grad from a target school. About 4 weeks ago I saw a posting for a great job at a big, reputable firm that I think suits me incredibly well. I would be excited to come to this job/group every day. I recently received an e-mail from a senior member of the group offering to interview me this coming week. The situation looks promising and I think I'd be a strong candidate.

The thing is, I started another job about 2 weeks ago at a mid market PE firm. It's a perfectly acceptable job, but definitely not something I'm excited to do everyday or something I'd want to turn in to a long-term career.

As much as I'd like to interview for the job, I feel like taking a day off or calling in sick 2 weeks + change into a new job would send up some red flags. How could I go about this without drawing suspiciouion from folks at my current firm?

I've been told that the interview would take about an hour. It's in the same city as my current job, but I'd have to take the subway to get there. As such, I'm assuming it might be hard to get it in during lunch.

Any advice would be appreciated, especially from anyone who's been in/knows people who've been in the same situation. Thanks in advance.