Layering with non-down parka?

I just got a Hetch Stretchy North Face parka (Gore-Tex and Primaloft). This is my first non-down parka. With down, all the way down to below zero, I just wear a thin polyester base layer and a mountain weight Hot Chili top. This jacket just feels so thin...will this be adequate, or do I need to add a fleece? I am skiing in the Northeast. So, for example, this weekend will be maybe 5 to 10 F plus wind chill.