Weather Alert in Pennsylvania
Special Weather Statement issued April 24 at 7:06AM EDT by NWS Pittsburgh PA
AREAS AFFECTED: Lawrence; Butler; Clarion; Jefferson; Beaver; Allegheny; Armstrong; Washington; Greene; Westmoreland; Westmoreland Ridges; Fayette; Fayette Ridges; Indiana; Higher Elevations of Indiana
DESCRIPTION: A combination of very warm temperatures, low relative humidity in the 20s (percent), and dry fine fuels and leaf litter will create an elevated risk of wildfire spread today across portions of Western Pennsylvania south of Interstate 80. The period of greatest potential for wildfire spread will be between 11 am and 7 pm today. Residents are urged to exercise caution if handling any potential ignition sources, such as machinery, cigarettes, or matches. If dry grasses and tree litter begin to burn, the fire will have the potential to spread rapidly. For more information about wildfire danger and wildfire prevention and education, please visit the Pennsylvania Department of Conservation and Natural Resources website at http://dcnr.pa.gov/Communities/Wildfire.
INSTRUCTION: N/A
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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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