Weather Tidbits: Advection Fog

We’ll be discussing advection fog in this addition of Weather Tidbits. Advection fog forms when relatively warm and moist air moves over a relatively colder surface. Many time the cold surface in question will have snow pack. As the warm moist air moves over the colder snow packed ground, it cools to saturation. When the air achieves saturation, the atmosphere can not carry any more moisture. So, it is condensed out into fog. This typically occurs with a warm frontal passage in the winter when there is snow on the ground. Advection fog can form under cloudy skies and with gusty winds. This is unlike radiation fog that you would typically see at night and the early morning, which favors calm conditions and clear skies.