The Mount Washington forecast makes entertaining reading. As I'm posting this comment, it says: "Looking further out, temperatures on Friday will start around 20F below then fall through the day to around 30F below at sunset. Temperatures continue to fall overnight, bottoming out after midnight and into early Saturday. How cold they get is still not quite nailed down as some models are keeping the bullseye of cold more to the northeast over Quebec while others have this sagging further south. On the high end, lows will bottom out at around 35F below while the low end has us bottoming out at around 43F below. There is even the hint of a tropopause fold in our vicinity and if that is the case, lows could dip even further for a brief period with one model this morning hinting at 49F below."