Air Masses &
Weather Fronts
Ms. Cervera
Bellringer # 4
1. How do yesterday’s observations relate to air masses?
2. What would happen if a warm air mass ran into a cold air mass?
Today you need:
Bellringer sheet
Blank paper
Pencil
WEATHER PATTERNS WORKSHEET
Lab worksheet
Today’s Objectives
Students will be able to…
 Classify the four major air masses that affect weather in the United States by
their characteristics
 Distinguish between and air mass and a front
 Describe how a weather front forms
Pressure Systems
 A high-pressure system is a large
body of circulating air with high
pressure at its center and lower
pressure outside of the system.
A low-pressure system is a large body
of circulating air with low pressure at
its center and higher pressure outside
of the system.
Stop & Think
Why do clouds usually form in the center of a
low-pressure system?
Air Masses
 Air masses are large bodies of air with distinct temperature and
moisture characteristics.
 An air mass forms when a large high pressure system lingers
over an area for several days.
 As a high pressure system comes in contact with Earth, the air
in the system takes on the temperature and moisture
characteristics of the surface below it.
Air Masses
 Air masses are classified by their temperature and moisture characteristics.
If an air mass forms over land, what type of air mass is
it?
What words would you use to describe an air mass
that formed over land near the equator?
Air Masses
 Five main air masses impact climate across North America.
 Continental air masses form over land.
 Maritime masses form over water.
Air Masses
 Five main air masses impact climate across North America.
 Tropical air masses form in the warm
equatorial regions.
 Polar air masses form over cold regions.
 Arctic and Antarctic air masses form near the
poles, over the coldest regions of the globe.
 Describe how a continental polar air mass can
change to a maritime polar air mass.
Stop & Think
What drives weather patterns?
Fronts
A weather front is a boundary between two air
masses.
Changes in temperature, humidity, clouds, wind,
and precipitation are common at fronts.
Fronts
 When a colder air mass moves
toward a warmer air mass, a cold
front forms.
 A warm front forms when lighter,
warmer air moves toward colder,
heavier air
Fronts (cont.)
 When the boundary between two
air masses stalls, the front is called
a stationary front.
 When a fast-moving cold front
catches up with a slow-moving
warm front, an occluded or blocked
front forms.
Exit Ticket
Imagine this:
A warm front is approaching Tallahassee. It is one day away.
What would you expect to observe regarding weather?
True or false:
A front that forms when a warm air mass meets a cold air mass is
an occluded front.
When cirrus clouds form close to the ground, the result is ground
fog.