Fronts
Goals:
1. To describe the formation of a front
2. To differentiate between the four different fronts
3. To describe weather patterns associated with each type of
front
Formation of fronts
 When two air masses meet, they form a front, which is a boundary that
separates two air masses.
 When a front occurs, it usually involves some sort of precipitation.
Fronts are much narrower than air masses. Between
15-200 km wide.
When air masses on both sides of a front move in the
same direction, the front acts as a barrier that
travels with air masses. ( Not typical)
Usually the pressure varies across a front
This causes one air mass to move faster than the
other
Causes the air masses to go into one another
Types of fronts
Fronts are classified according to the
temperature of the advancing front.
There are four types of fronts.
Warm fronts
Cold fronts
Stationary fronts
Occluded fronts
Warm fronts
 A warm front forms when warm air moves into an area
formerly covered by cooler air
 The slope on a warm front is very gradual
As warm air rises, it cools to produce clouds and
sometimes a form of precipitation
The first sign that a warm front is coming is the
appearance of cirrus clouds
These then change into cirrostratus clouds
Which turn into altostratus clouds
Which turn into stratus and nimbostratus clouds and
produce rain or snow
Warm Fronts Cont.
Affects of warm fronts
Produce light to moderate precipitation
over a large area for a long time
This is because their slow rate of
movement
A gradual increase in temperature
Wind shift- The wind shifts from east to
southwest
Cold Front
 A cold front forms when cold, dense air moves into a
region occupied by warmer air.
 Colds fronts are about twice as steep as warm fronts
Advance faster than warm fronts
This is why there is more violent weather associated
with cold fronts.
 Cold fronts lead to:
Heavy downpours
Gusty winds
Drop in temperature
Stationary fronts
When the flow of air on either side of a front is
neither toward the cold air mass nor toward the
warm air mass.
This is known as a stationary front because it
does not move
Gentle to moderate precipitation may occur
along a stationary front
Occluded fronts
When an active cold front overtakes a warm front,
an occluded front forms
Develops as the faster moving cold air wedges
the warm front and causes it to move upward
Associated weather
Precipitation due to the warm air being forced
up
Precipitation- due to the front creating it on its
own
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