section_path: Precipitation/Cloud formation/Fronts
section_name: Fronts
paragraph_text: Fronts
  
  A cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls —an intense frontal convective line (similar to a rainband), when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which the line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, but the motion of the line can cover large distances. Frontal squalls may form a short distance ahead of the surface cold front or behind the cold front where there may be a deepening low-pressure system or a series of trough lines which act similar to a traditional cold frontal passage. In situations where squalls develop post-frontally, it is not unusual to have two or three linear squall bands pass in rapid succession separated only by 25 miles (40 kilometers), with each passing the same point roughly 30 minutes apart. In cases where there is a large amount of vertical growth and mixing, the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow.
  
  A warm front can produce snow for a period as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Often, snow transitions to rain in the warm sector behind the front.