Print twice for a complete mold. Larger nozzle sizes are strongly recommended for the bigger models. Best printed out of PETG, with 100% perimeters (instead of infill) and standing up straight with a large brim. Be mindful of the top of the head, due to the significant overhang.

I have printed mine with a 0.8n @ 0.55l.
 

For wet snow, fill both halves of the mold to the brim and press together. If you're working with powder snow, bury the molds in it and plow them through the snow towards each other several times, thoroughly compressing the snow inside the mold each time.

You can try rotating either half around its vertical axis by a few degrees to help unstick the snow from the mold or to remove any snow stuck between the edges. Slightly squeeze either half to demold the snowman.

If you're having trouble with snow sticking to the mold, try using silicone oil as a release agent.

You can get the model of the hat from here.