Understanding Weather Terms
The National Weather Service has supplied some definitions for several weather phrases common in Northern Arizona.
- Advisory: a weather event may threaten life or property if caution is not exercised.
- Blowing Snow: wind-driven snow that significantly reduces surface visibility to less than 7 miles.
- Breezy: sustained wind speeds of 15-25 mph.
- Chance: a 25-55% probability that one point in a forecast area will have precipitation.
- Flurries: light snowfall that generally does not produce measurable accumulation.
- Freezing Drizzle or Rain: the effect of drizzle or rain upon impact on objects that have a temperature of 32 degrees or below.
- Frost: a covering of small ice crystals that forms on or near the ground when temperatures approach or drop below 32 degrees.
- Hail: Precipitation in the form of balls or lumps usually consisting of concentric layers of ice. A thunderstorm is classified as severe when it produces hail 3/4 inch in diameter.
- Humidity: amount of water vapor in the atmosphere.
- Ice Storm: a freezing rain event that produces damaging ice accumulations of 1/4 inch or greater.
- Likely: a 55-75% probability that one point in a forecast area will have precipitation.
- Numerous: showers or thunderstorms with 55-75% area coverage.
- Rain: a nearly steady and uniform fall of liquid precipitation over an area for several hours.
- Scattered: showers or thunderstorms with 25-55% area coverage.
- Severe Thunderstorm: produces or exceeds either of the following: damaging winds of 58 mph, hail 3/4 of an inch in diameter or tornado.
- Shower: intermittent rain or snow.
- Sleet: solid grains of ice formed by the freezing of raindrops or the refreezing of largely melted snowflakes.
- Slight Chance: 1-25% probability that one point in a forecast area will have precipitation.
- Snow: steady fall of snowflakes for several hours over the same area.
- Snowpack: combined layers of snow and ice on the ground at any one time.
- Snow Showers: snow that stops and starts suddenly and is characterized by rapid changes in both intensity and visibility.
- Sustained Wind: wind speed determined by averaging observed values over a 1-minute period.
- Warning: indicates a hazard weather element is imminent or has a very high probability of occurrence.
- Watch: alerts the public to the possibility of severe weather, or some other hazardous weather element.
- Wind Chill: apparent temperature that describes the combined effect of wind and low air temperatures on exposed skin.
- Windy: sustained winds speeds of 20-30 mph.