• Winter Weather Awareness (3)

    From Daryl Stout@1:2320/105 to All on Tue Nov 30 00:01:36 2021
    Public Information Statement
    National Weather Service Little Rock AR
    600 AM CST Tue Nov 30 2021

    November 29th through December 3rd is Winter Weather Awareness
    Week in Arkansas. The purpose of this week is to remind people
    what winter weather can bring, and how to deal with
    hazardous winter conditions. Now is the time to prepare
    for the upcoming winter season.

    Today's topic is winter precipitation types.

    Snow -- Snow forms in the clouds and remains as snow all the way to
    the ground. It most commonly takes the form of snowflakes, which
    are the familiar six-sided ice crystals. It may also fall in the
    from of snow pellets or snow grains.

    Snow flurries are normally seen as a few snowflakes falling, although visibilities can be reduced at times. In Arkansas, the term snow
    flurries is used to indicate that no accumulation is expected.

    Snow showers is a term not often used in Arkansas. Given this type
    of precipitation, snow falls at varying rates, often changing
    intensities over brief periods. Accumulation may occur, especially
    during moderate to heavy snow showers.

    Blowing snow refers to snow that is already on the ground and is
    lifted into the air by the wind.

    In Arkansas, heavier snows usually occur when cold air is already
    in place over the state and a strong upper level low pressure
    system moves out of the southwestern United States. The low serves
    to pull moist air from the Gulf of Mexico northward into the cold
    air. Light snow or snow flurries can also occur in the cold air that
    follows the passage of an Arctic cold front.

    Sleet -- Sleet consists of pellets of ice. In fact, for people who
    have trouble with the difference between sleet and freezing rain, it
    may be easier to associate sleet with its technical name, which is
    ice pellets. For sleet to form, snow begins falling from the clouds
    but then goes through a layer of above-freezing air thousands of
    feet above the ground. This causes the snow to change to rain. Then,
    the rain goes through a layer of below-freezing air, usually at least
    two to three thousand feet thick, and the precipitation turns into
    pellets of ice.

    Sleet typically occurs in a fairly narrow band between an area of
    rain to the south and snow to the north. This band usually
    moves as the temperature profile changes, but may remain nearly
    stationary if temperatures fail to fluctuate. This often results
    in accumulations of sleet.

    Freezing rain -- This weather phenomenon is sometimes called glaze,
    because of the glaze of ice that builds up on surfaces near the ground. Freezing rain normally occurs when precipitation falls from the clouds
    as snow, then goes through an above-freezing layer, which turns the precipitation to rain. Then, the rain reaches the ground where
    temperatures are below freezing. The rain then freezes as it hits
    exposed objects. In the worst cases, everything becomes coated with
    a layer of ice.

    In Arkansas, freezing rain commonly occurs as an Arctic high pressure
    system begins to move away from the state. In this situation, cold
    air is still lingering at the ground, but warmer southerly winds
    from the Gulf of Mexico begin bringing moisture back over the top
    of the cold air. Since the air at the ground has not warmed above
    freezing, the rain that falls freezes on the ground and other objects. Freezing rain, and its cousin freezing drizzle, often develop during
    the late night hours, creating icy conditions for morning rush hour.

    Freezing Fog -- While this is not precipitation falling from the
    clouds, it is another winter weather hazard. Freezing fog typically
    develops on clear, calm nights when temperatures are below freezing.
    Fog forms and freezes, usually on bridges, overpasses, and other
    elevated roadways. The resulting thin layer of ice can create
    quite a surprise for motorists due to the presence of clear skies

    Frost -- Frost describes the formation of thin ice crystals on the
    ground or other surfaces in the form of scales, needles, feathers,
    or fans. Frost forms when water vapor in the air turns directly
    to ice crystals on an object. The temperature of the object must be
    below freezing for frost to occur. However, frost is sometimes seen
    on the ground when official temperatures are reported to be above
    freezing. This is because the official temperature is taken about
    five feet above the ground, where the air can be a few degrees
    warmer than the temperature at ground level.


    Please visit our web site at https://www.weather.gov/lzk

    * Synchronet * The Thunderbolt BBS - Little Rock, Arkansas
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