Weather Alert in Arizona
Air Quality Alert issued April 29 at 9:30AM MST by NWS Phoenix AZ
AREAS AFFECTED: Maricopa, AZ
DESCRIPTION: AQAPSR The Arizona Department of Environmental Quality (ADEQ) has issued an Ozone High Pollution Advisory for the Phoenix Metro Area on Wednesday. This means that forecast weather conditions combined with existing ozone levels are expected to result in local maximum 8-hour ozone concentrations that pose a health risk. Adverse health effects increase as air quality deteriorates. Ozone is an air contaminant which can cause breathing difficulties for children, older adults, as well as persons with respiratory problems. A decrease in physical activity is recommended. You are urged to car pool, telecommute or use mass transit. The use of gasoline-powered equipment should be reduced or done late in the day. For details on this High Pollution Advisory, visit the ADEQ internet site at www.azdeq.gov/forecast/phoenix or call 602-771-2300.
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Weather Topic: What is Precipitation?
Home - Education - Precipitation - Precipitation
Next Topic: Rain
Precipitation can refer to many different forms of water that
may fall from clouds. Precipitation occurs after a cloud has become saturated to
the point where its water particles are more dense than the air below the cloud.
In most cases, precipitation will reach the ground, but it is not uncommon for
precipitation to evaporate before it reaches the earth's surface.
When precipitation evaporates before it contacts the ground it is called Virga.
Graupel, hail, sleet, rain, drizzle, and snow are forms of precipitation, but fog
and mist are not considered precipitation because the water vapor which
constitutes them isn't dense enough to fall to the ground.
Next Topic: Rain
Weather Topic: What are Shelf Clouds?
Home - Education - Cloud Types - Shelf Clouds
Next Topic: Sleet
A shelf cloud is similar to a wall cloud, but forms at the front
of a storm cloud, instead of at the rear, where wall clouds form.
A shelf cloud is caused by a series of events set into motion by the advancing
storm; first, cool air settles along the ground where precipitation has just fallen.
As the cool air is brought in, the warmer air is displaced, and rises above it,
because it is less dense. When the warmer air reaches the bottom of the storm cloud,
it begins to cool again, and the resulting condensation is a visible shelf cloud.
Next Topic: Sleet
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