ELMIRA, N.Y. (WETM) – Last week we touched on radiation fog but there is actually two different types and it all really depends on the season. Advection fog is the opposite of radiation fog. During the advection fog set up, we need incoming warm and moist air. The best for this set up is during the wintertime when the ground is cold. Typically the best way to get this is with snowpack already on the ground. As the warm and moist air that is moving in passes over the cold ground, it is cooled to saturation. This creates the fog just above the snowpack. This fog can also freeze on surfaces that are still below freezing. This type of fog typically occurs during a warm front passage in the winter time. To review radiation fog click here.