4.  The boundary of air masses of different temperatures  When 2 different air masses meet, they do not usually mix together, but crash into each other  4 Types of weather fronts: ◦ Cold fronts ◦ Warm fronts ◦ Stationary fronts ◦ Occluded fronts

5. Cold Fronts: Temperature is lower behind a cold front Cold air pushes warm air higher Precipitation (rain or snow) usually occurs at a cold front when warm air is pushed up http://www.mesoscale.iastate.edu/agron20 6/animations/05_cnWfronts.html http://www.mesoscale.iastate.edu/agron20 6/animations/05_cnWfronts.html

6. Warm Front: Warm air pushes up higher as it passes colder air Clouds are seen high in the sky Rain is possible when the warm air over the cold air cools and condenses.

7. Stationary front: Cold front and a warm front meet and they don’t move Usually has the same weather as a warm front- high clouds with some chance of rain once the warm air cools and condenses.

8.  Occluded front: ◦ Occurs when a cold front overtakes a warm front ◦ This happens because cold fronts move faster than warm fronts ◦ Both fronts are moving in the same direction-the cold front catches up to the warm front

11. Low Pressure (L): Air rises and cools ◦ forms clouds because of condensation ◦ Rain is likely ◦ http://www.juicygeography.co.uk/downloads/flash /lowpressure.swf http://www.juicygeography.co.uk/downloads/flash /lowpressure.swf High Pressure (H): Air sinks and warms ◦ Clouds disappear ◦ No Rain ◦ http://www.juicygeography.co.uk/downloads/flash /highpressure.swf http://www.juicygeography.co.uk/downloads/flash /highpressure.swf