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.