12.8 NOTES
What is a front?
Describe the different kinds of fronts and the weather they cause
A front is the boundary between two air masses of different densities. In the
United States, air masses usually travel west to east. As they move, they meet up
with other air masses.
Fronts form between individual air masses, bringing changes in the weather.
A cold front is the
forward edge of a
cold air mass. It is
formed from a cold
air mass pushes its
way underneath a
warm air mass. Cold
fronts usually bring
rain and cloudy skies.
A warm front is the forward edge of a warm air mass. It forms when a warm air
mass pushes over a cooler air mass. The warm air moves slowly up and over the
cold air. When it
cools, cirrus clouds
may form and
precipitation may
follow.
Sometimes cold and
warm fronts do not
move for a while.
This is called a
stationary front. It
brings very little
change in the
weather.
The most complex weather situation occurs with occluded fronts. This is when a
warm air mass is between two cooler air masses. Cooler air pushes the warm air
up cutting off the warm air from touching the ground. As the warm air cools, it
condenses. An occluded front brings cloudy, rainy, or snowy weather.