This week, we've observed dense fog every night, prompting many to ask, "Why has it been so foggy?" The combination of a melting snowpack, abnormally warm temperatures, and a relatively moist air mass aloft have all contributed to the fog this week. Several types of fog exist, but the fog we've experienced this week occurred when warm air overran cold air. Surface winds have been calm this week, but at 3,000 feet, winds are coming in from the southwest, a warm/moist source region (i.e., the Gulf). At the ground, we have a melting snowpack, which keeps the ground cool. As the relatively warm air aloft comes into contact with the cold, snow-covered ground, the air condenses, and fog forms!
