bri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4 Reply 2, posted (3 years 9 months 3 weeks 6 days 12 hours ago) and read 1524 times:
Snow in fog occurs routinely here in Colorado on the eastern slope of the Rocky Mountains. When snow begins to fall, the ground is warmer than the air, creating radiation fog with enough humidity. The snow falls from clouds high above the dense ground fog. In many snow conditions, the front is stable, helping to ensure low surface winds, further promoting fog development. Pacific storms don't generally have enough moisture to cause this, but the upslope flow from Gulf storms in the spring usually do. The National Weather Service will call this as fog, but depending on the air temperature near the surface, can also refer to it as light snow with mist and associated reduced visibility.