Don't let the Nav pick your charging stops: just navigate directly to the next supercharger from the one you're charging at. With temperatures that low, you will want to charge until the Trip graph in the Energy app shows that you'll arrive with at least 30% battery remaining (it doesn't take into account the weather). If there is snow on the road or strong headwinds/crosswinds, make that 50%. If you reach full charge before you have the desired buffer, drive really slowly (no more than 55mph) until you have a sense for how things are going.
Another thing that will help your range is to pre-heat the interior of the car to much warmer than you would ordinarily, while attached to the Supercharger. Then you can take advantage of the thermal energy stored in the interior of the car without using a lot of battery power to keep you warm during the first stretch after you leave the charger. Bundle up, and try using the seat heaters and the steering wheel heater (if so equipped), and turn the climate control off completely for the first miles.