Weather Forecasting
Making Predictions About Our
Weather
Air Masses
• Air Mass - a very large region area of air with the
same temperature and humidity
• Words to describe air masses:
– warm
– cold
– wet
– dry
Moving Masses = Fronts
• The wind pushes these air masses into each other.
• This causes many things:
– Precipitation changes
– Temperature changes
– Clouds form or change
– Fronts are formed
• Front – a boundary where two air masses meet
Cold Fronts
• Cold Front – a boundary
where a cold air mass
pushes under a warm air
mass
• The warm air rises and
cumulus clouds form.
• Dark clouds, rain, and
maybe storms follow.
• Colder air comes behind
the front, so
temperatures drop.
Cold air coming
in. This makes the
temps
decrease.
Warm air
rises and
leaves the
area. As
it rises, it
cools and
creates
clouds.
Think of it like your house: If you turn off the heat
and turn on the AC, your house gets cooler. You added
cooler air and took away warmer air.
Warm Fronts
• Warm Front – a
boundary where a warm
air mass slides up and
over a cold air mass
• As the warm air slides
over, it makes long, thin
stratus clouds.
• Rain usually follows,
though not heavy.
• Warm fronts bring in
warmer air, so temps
increase.
Warm air
enters the
area and
pushes out
the cooler
air that was
there. This
makes the
temperature
of the area
increase.
The warm
air spreads
slowly over
the cold air.
This creates
thin, stratus
clouds. Rain
is common,
but nothing
heavy.
Think of your house again: If you crank up the heat and
turn off the AC, your house gets warmer. You have added
warm air and taken away cold air.
Stationary Front
• Stationary Front – a
boundary where a cold
air mass and warm air
mass meet, but neither
one moves the other
• In other words, the front
doesn’t move. The air
masses “tie.”
• This causes long periods
of the same weather and
precipitation.
• Can cause flooding.
Stationary Front
Two air masses have met, but neither one is pushing
the other. This usually happens when the wind
decreases and a cold or warm front stops moving.