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 comingin. This makes the temps decrease.

Warm airrises andleaves thearea. Asit rises, itcools andcreatesclouds.

Think of it like your house: If you turn off the heatand turn on the AC, your house gets cooler. You addedcooler 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 thearea andpushes outthe coolerair that wasthere. Thismakes the temperatureof the areaincrease.

The warmair spreadsslowly overthe cold air.This createsthin, stratusclouds. Rainis common,but nothingheavy.

Think of your house again: If you crank up the heat and turn off the AC, your house gets warmer. You have addedwarm 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 pushingthe other. This usually happens when the wind decreases and a cold or warm front stops moving.