What is the difference between a National Weather Service advisory, statement, watch, and warning?

The National Weather Service will issue a statement as a "first alert" of a major change in the weather. An advisory is issued when weather conditions are not life threatening, but individuals need to be alert to weather conditions. A weather watch is issued when conditions are more favorable than usual for dangerous weather conditions, e.g. tornadoes and violent thunderstorms. A watch is a recommendation for planning, preparation, and increased awareness (i.e., to be alert for changing weather, listen for further information, and think about what to do if the danger materializes). A warning is issued when a particular weather hazard is either imminent or has been reported. A warning indicates the need to take action to protect life and property. The type of hazard is reflected in the type of warning (e.g., tornado warning, blizzard warning).

What is the Storm Prediction Center (SPC)?

A part of the National Weather Service and the National Centers for Environmental Prediction, the Storm Prediction Center focuses its efforts on forecasting only hazardous weather, including heavy rains and snows, as well as conditions that could lead to dangerous wildfires.

How do meteorologists come up with percentages predicting the weather?

We've all heard weather broadcasts where a meteorologist will say something such as "This afternoon there will be a 40 percent chance of snow showers" or "A 75 percent chance of rain will likely make it a wet night," but how do they come up with these figures? To many audiences this might seem like mere guesswork on the part of the television weather people. Actually, they arrive at such figures using a series of computer models. What typically happens is that a meteorologist will gather together as much data as possible from local and national weather stations, including from weather satellites, Doppler radar, temperature readings, etc., feed this data into a computer weather modeling program, and run dozens of scenarios of what could happen given these initial conditions. If, for instance, 20 out of 60 of the scenarios that are run predict that there will be rainfall, then the meteorologist will predict a 30 percent chance of rain. While chaos theory dictates that there is no reasonable way one can expect meteorologists to have a 100 percent—or even a 90 or 80 percent—accuracy rate, they come as close as possible given our current knowledge of how weather works and the limitations even computer technology has.

What do meteorologists mean when they talk about POP?

POP is an abbreviation for "probability of precipitation."

Is there a difference between a forecast of partly sunny or partly cloudy skies?

Yes. The difference is that "partly cloudy" refers to a sky that is mostly clear with some clouds in it, while "partly sunny" is a sky that has more cloud cover than clear patches.

What is NOAA Weather Radio?

The National Oceanic and Atmospheric Administration's Weather Radio is a 24-hour-a-day broadcast of weather conditions throughout the United States (about 90 percent of the lower 48 states are covered), including its territories. Working in conjunction with the Emergency Alert System and the Federal Communications Commission, as well as other federal, state, and local officials, Weather Radio also broadcasts warnings about other hazards, such as earthquakes and tsunamis, or environmental accidents (oil or chemical spills, for example), and public service announcements like AMBER Alerts about missing children.

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