WINTER AND FALL WEATHER TERMINOLOGY

  • BLIZZARD WARNING: Blizzard Warning:Issued for winter storm with sustained or frequent winds of 35 mph or higher with considerable falling and/or blowing snow that frequently reduces visibility to one quarter (1/4) of a mile or less. These conditions are expected to prevail for a minimum of three (3) hours.
  • BLOWING SNOW ADVISORY: Issued when wind driven snow reduces surface visibility, possibly hampering traveling. Blowing snow may be falling or has already accumulated but is picked up and blown by strong winds.
  • DRIFTING SNOW: An uneven distribution of snowfall or existing snow caused by strong surface wind. Drifting snow may occur during or after a snowfall.
  • FREEZE: A condition occurring over a large area when the surface air temperature remains below thirty two (32) degrees Fahrenheit for an extended period of time possibly leading to damage of certain crops.
  • FREEZE WARNING: Issued during the growing season when surface temperatures are expected to drop below freezing over a large area for an extended period of time, regardless if frost develops or not.
  • FREEZING DRIZZLE/RAIN ADVISORY: Issued when freezing rain or freezing drizzle is forecast but a significant amount of it is not expected. However, even small amounts of freezing rain or freezing drizzle may cause traveling problems.
  • FREEZING DRIZZLE: Drizzle that falls in liquid form and then freezes upon impact with the ground or an item with a temperature of thirty two (32) degrees Fahrenheit or less, possibly producing a thin coating of ice. Even in small amounts, freezing drizzle may cause traveling problems.
  • FREEZING RAIN: Rain that falls in a liquid form and then freezes upon impact with the ground or an item with a temperature of thirty two (32) degrees Fahrenheit or less, possibly producing a thin coating of ice. Even in small amounts, freezing rain can cause traveling problems. Large amounts can pull down power lines and tree branches.
  • FROST: A covering of ice on exposed surfaces when air temperature falls below the frost point.
  • FROST ADVISORY: Issued during the growing season when widespread frost formation is expected over an extensive area. Surface temperature are usually in the mid thirties (30s) Fahrenheit.
  • FROST POINT - When the temperature to which air must be cooled to in order to be saturated is below freezing.
  • FROZEN DUE: When liquid due changes into tiny beads of ice. The change occurs after dew formation and then the temperature falls below freezing.
  • HEATING DEGREE DAY: A form of degree day used to estimate the required energy for heating. One heating degree day occurs for each degree the mean temperature is below sixty five (65) degrees Fahrenheit.
  • HEAVY SNOW WARNING: Issued when snowfall totaling six (6) inches or more in twelve (12) hours or less is expected. Also issued when snow fall totaling eight (8) inches or more in twenty four (24) hours or less expected.
  • ICE CRYSTALS: A barely visible crystalline form of ice that has the shape of needles, columns or plates. Ice crystals are so small that they seem to be suspended in air. Ice crystals occurs at very low temperatures in a stable atmosphere.
  • ICE FOG: Fog composed of ice crystals instead of water droplets. Ice fog forms when clear and calm conditions prevail in extremely cold arctic air.
  • ICE STORM WARNING - Issued when damaging accumulations of ice are expected during a freezing rain event. Significant ice accumulations are one quarter (1/4) if an inch or greater leading to dangerous walking or driving conditions and pulling down of power lines and trees.
  • SNOW: Precipitation composed of white or translucent ice crystals. Snow forms in cold clouds by the direct transfer of water vapor to ice.
  • SNOWFLAKE: White ice crystals that have combined in a complex branched hexagonal form.
  • SNOW ADVISORY: Issued when snowfall is expected to exceed two (2) inches but not expected to exceed five (5) inches. A snow advisory may also be issued for snowfalls under two (2) inches if occurring at the beginning of a snow season or after a prolonged period between snowfall events.
  • SNOW FLURRIES: Intermittent snowfall of short duration. No measurable accumulation of snow occurs.
  • SNOW SHOWER: A short duration of light to moderate snowfall. Accumulations of snow are possible.
  • SLEET: Precipitation consisting of transparent pellets of ice, five (5) millimeters of less in diameter. Also called ice pellets. Forms when snow enters a warm layer of air above the surface and melts and then enters a deep layer of sub freezing air on the surface and refreezes.
  • SLEET WARNING: Issued when accumulation of sleet in excess of one half (1/2) inch is expected. Relatively rare. Usually issued as a winter storm warning for heavy sleet.
  • WIND CHILL FACTOR: The apparent temperature which describes the cooling effect on exposed skin by the combination of temperature and wind, expressed as the loss of body heat. Increased wind speed will accelerate the loss of body heat. A wind chill factor of thirty (30) degrees or lower on exposed skin will result in frostbite in a short period of time.
  • WIND CHILL ADVISORY: Issued when winds of ten (10) mph or greater are expected to create wind chill factors of thirty (30) degrees below zero or more.
  • WINTER STORM WARNING: Issued when hazardous winter weather is occurring, imminent or highly likely over part or all of the area. Hazardous winter weather includes but is not limited to heavy snow, blizzards, ice storms, freezing rain or drizzle and sleet.
  • WINTER WEATHER ADVISORY: Issued for winter weather situations that may cause significant inconvenience and, if caution is not exercised, could lead to life threatening situations. Issued when events are occurring, imminent or highly likely to occur. Issued when a combination of five (5) inches or less of snow, freezing precipitation and/or sleet in expected. Also issued for a combination of sleet and freezing precipitation light enough not to bring down trees, branches or power lines.
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