In reply to sharpie530:
I've worn the Extreme Smock for skiing when it's been very cold, with a merino base layer underneath (I know it's supposed to be used without, blah blah, but I don't like being blasted by icy spindrift). The side and cross vents allow you to dump heat, and you can open the thing up completely at cafe stops.
The Resolute is more water resistant than the Extreme; that'll make it feel warmer (don't try to have the two product pages open at once, as there's a bug in Montane's website that causes the same details to be shown for two different items; fooled me the other day...). I prefer the idea of the water resistant zips to the zip and velcro flaps of the Extreme; mine's a bit of a PITA, with rough Velcro I keep meaning to change. The WR zips look like less faff, and the whole things looks a bit 'tidier'.
But, generally, I prefer to wear something lighter (shelled micropile or MixMaster), and carry a 60gsm Primaloft overlayer in a little MTB pack.
Depends on how hot you run, and how active you are when skiing, but, in January, I think you'll be fine.