A snow flurry is a brief gust of wind accompanied by a light burst of snow, which does not usually remain lying on the ground. It is common in most cold climates and not unheard of in temperate ones. Other, similar, phenomena are snow squalls, which involve a brief, but heavy, fall; and snow showers, which feature a short-lived, moderate fall, with some accumulation on the ground. Accompanied by wind, the snow may travel some distance, and sometimes take the bystander by surprise, seemingly appearing out of nowhere on a perfectly sunny day and blasting the unsuspecting with a brief shot of bitter cold. Often, snow flurries indicate that a more serious weather front is on the way.
Generally, snow from flurries does not produce a ground covering, as it melts on contact with the surface, and will disappear almost as quickly as it appeared. When the snow falls on ground that is already covered, however, it usually sticks, because the ambient temperature is already far enough before the freezing point to allow it to remain without melting. Especially in temperate climates, this phenomenon can be quite exciting, because people usually only see rain or occasional sleet in the winter. People in some urban areas, such as San Francisco, which rarely experiences snow, may be momentarily shocked by this occasional meteorological event.
Origin
Snow is a common meteorological phenomenon and a crucial part of the water cycle. When water evaporates, it cycles up into the sky, where it often reforms into droplets, seen in the form of clouds. When the droplets become heavy enough, they fall as rain. However, if it is cold enough, the droplets freeze to form snow crystals. If the temperature remains low all the way down, the droplets will retain their crystal formation.
Snow flurries are caused by isolated patches of cloud where droplets have frozen. Like squalls and showers, they are associated with convective, or cumulus, type clouds, rather than the stratiform, or layered, flat clouds that produce steady snowfall. Since they are usually small, snow flurries are difficult to predict, and they generally do not show up on weather radar or at weather observation stations. They are also usually too short-lived to be noted. Anyone witnessing this event should probably run outside quickly to experience it, or he may miss it.
Hazards
Usually, snow flurries are not dangerous, although they can be disconcerting. In some cases, this weather might pose a hazard to unprepared drivers who have to contend with brief limited visibility and possibly a slurry of snow on the roads that will change the way a vehicle handles. Injury due to exposure is rare in the case of a snow flurry, although the brief compromise to visibility and increased slipperiness may lead to pratfalls. In general, however, snow flurries are merely surprising, and sometimes pleasantly playful.
