depression

• low pressure

  the air masses are lifting off the ground, creating low pressure.
• winds travel in a anticlockwise direction.
• wind speeds are high.

  the isobars are close together.
• no fog develops

  the wind blows away any developing fog.
• a warm front develops.


  this happens when warmer air pushes colder air.
• a cold front develops 


  this happens when colder air pushes into warmer air.
• prolonged mid-intensity rain comes first


  this develops along the warm front as air is forced to rise, cool, condenses to form nimbostratus clouds.
• clear sky (perhaps drizzle) follows 


  after the warm front passes a few small cumulus clouds may release drizzle.
• a short burst of high intensity rain (perhaps thunderstorms) comes later.


  this develops along the cold front as air is forced to rise very rapidly, causing cooling and condensing to be faster and causing cumulonimbus clouds to form.