Editing Surface weather analysis (section)

==== Warm front ====

{{Main|Warm front}}

[[Warm front]]s mark the position on the Earth's surface where a relatively warm body of air is advancing into colder air. The front is marked on the warm edge of the gradient in isotherms, and lies within a low pressure trough that tends to be broader and weaker than that of a cold front. Warm fronts move more slowly than cold fronts because cold air is denser, and is only pushed along (not lifted from) the Earth's surface. The warm air mass overrides the cold air mass, so temperature and cloud changes occur at higher altitudes before those at the surface. Clouds ahead of the warm front are mostly [[Stratus cloud|stratiform]] with precipitation that increases gradually as the front approaches. Ahead of a warm front, descending cloud bases will often begin with [[Cirrus cloud|cirrus]] and [[Cirrostratus cloud|cirrostratus]] (high-level), then [[Altostratus cloud|altostratus]] (mid-level) clouds, and eventually lower in the atmosphere as the front passes through. [[Fog]] can precede a warm front when precipitation falls into areas of colder air, but increasing surface temperatures and wind tend to dissipate it after a warm front passes through. Cases with environmental [[Convective instability|instability]] can be conducive to thunderstorm development. On weather maps, the surface location of a warm front is marked with a red line of half circles pointing in the direction of travel.

[[Image:Warmfrontai.svg|thumb|Illustration clouds overriding a [[warm front]]]]