For they making Snow, in Tools, SKy maker, there is a tab called "Cycle" where you can load the default weather file and just change it from rain to snow.
As for the portal, It's a bit tircky. In Mapmaker, you'll see a section that says "Has Portal", check that off. In the Y X Z and arrival yaw, you type numbers in there so the portal is gradually moved onto the map. For one reason or another the only way you can see the portal is to be in Test mode, so you'll just have to keep adding and checking until it's at the spot you want it to be.
