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Unit 2: Fronts

What are fronts? These are just boundaries between air masses of different temperatures.

Cold: This is a type of front where cold air is replacing warmer air at the surface.

  • They can cause a drastic change in the weather and move quite fast.
  • As a cold front moves in the cold, dense air pushes under the lighter, warm air. This lifting warmer air causes thunderstorms and stormy clouds to form ahead of the front. Winds will start to gust up as the cold front is pushing through and can cause a sudden drop in temperature.
  • A cold front is represented by a blue line with filled in blue triangles on it. The triangles point in the direction that the front is moving.

Warm: This is a type of front when a warm air mass pushes into a colder air mass.

  • These can often bring stormy weather as well. That warm air mass will rises above the colder air mass creating clouds and storms. They moves much slower than cold fronts because it is harder for a less dense, warmer mass of air to push a more dense colder air mass.
  • Most of the time you will see fair weather clouds ahead of the front and as the front passes, lower clouds will form and will likely cause rain and storms.
  • This is represented with a red line, filled in red, half-circles. The half-circles again point in the direction in which the front is moving.

Stationary: This type of front is formed when a cold or warm front stops moving.

  • Two masses of air are pushing against each other, but neither has enough power to overtake the other one. This can stay in the same place for days until the front can start moving again, normally from a change in wind direction or the front could just dissipate.
  • On either side of the stationary front, the weather can be drastically different.
  • This front is represented with alternating red half-circle and blue triangles pointing in the opposite direction

Occluded: A cold from can sometimes follow behind a warm front.

  • Cool air from the cold front will meet the cooler air in front of the warm front. Warm air rises as these air masses come together.
  • Normally, precipitation is associated with this type of front and will be connected to an area of low pressure.
  • This is represented by alternating half-circles and triangles in purple.