Evaporation or Mixing Fog - This type of fog forms when sufficient water vapor is added to the air by evaporation, and the moist air mixes with relatively drier air. The two common types are steam fog and frontal fog. Steam fog forms when cold air moves over warm water. This type of fog takes on the appearance of wisps of smoke rising off the surface of the water. The other type of evaporation fog is known as frontal fog. This type of fog forms when warm raindrops evaporate in a cool air mass near the ground.

Psychrometer - An instrument used to measure the water vapor content of the air. The first pantented instrument that was coined a "psychrometer" was invented in 1818 by a German inventor named Ernst Ferdinand August.

Deposition - The process where water turns directly from vapor to ice, without first becoming liquid. A common instance of deposition is when frost forms on the grass during cold mornings.

Avalanche - A large mass of rapidly moving snow down a steep mountain slope. Most avalanches are triggered by the people that become victim to them. On average, around 150 people are killed by avalanches each year.

Ice Fog - This type of fog forms when the air temperature is well below freezing and it's composed entirely of tiny ice crystals that are suspended in the air. Ice fog will only be witnessed while in the midst of an arctic air mass. Generally, the temperature needs to be 14F or colder in order for ice fog to form.

Tropopause - Zone of the atmosphere that marks the transition between the troposphere below and the stratosphere above. The tropopause is the top of the troposphere. 75 percent of the mass of the atmosphere is located below the tropopause. The height of the tropopause varies between 4 to 12 miles.

Precipitable Water - This takes into account all the water vapor that is found in the atmosphere from the surface to a specified height. Precipitable water is the amount of liquid precipitation that would occur if all the water vapor were condensed. The measurement is given in inches of rain. Precipitable water values are watched closely by meteorologists when diagnosing the potential for heavy rains during weather events.