how do blizzards form

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					                     What causes blizzards?

Blizzards are obviously related very closely to hurricanes,
tornadoes, and weather fronts. For a blizzard to occur, there must
be precise amounts of each of these things.

Snow storms can be caused by a warm front coliding with a cold
front. This creates a low pressure zone. When clouds in the low
pressure zone are filled with ice crystals, there are chances for a
major blizzard. (Note: a warm front is basically a warm wind, and
a cold front it a cold wind. When the two winds colide, they
neutralize each other out in a way, and make a low pressure zone.)

Low pressure creates high powered winds, as the warmer air
spirals into the low zone, and adds alot of movement. Therefore if
a low pressure zone gets lower, the winds speed up.

For snow, there needs to be alot of moisture in the air. This can be
gathered up if the low pressure zone goes over a large body of
water, like an ocean or lake. This moisture will then cool off as it
rises into the atmosphere.
                                        How does snow form?

                                        Snow goes through a bit of change before
                                        it lands on the ground. First off, it starts in
                                        a very humid system (a lot of moisture).
         QuickTime™ a nd a              Then, the whole system has to fly over a
TIFF (Uncompressed) decompressor        cold pocket of air. Then, the moisture
   are need ed to see this picture.
                                        turns to ice crystals. Then the ice crystals
                                        combine together to form snow flakes.
                                        Finally, as soon as the snow flakes get too
                                        big to stay in the air, they fall to the
                                        ground.



                           What is a blizzard?

A blizzard is defined as "A severe weather condition that is
distinguished by low temperatures, strong winds, and large
quantities of snow." (Encyclopedia Britannica at britannica.com)

                                          More simpily put, a blizzards is
                                          alot of snow in very cold weather.
             QuickTime™ an d a
                                          To be a blizzard, it must have
    TIFF (Uncompressed) decompressor
       are need ed to see this p icture . winds with speed of 32 miles an
                                          hour, and enough snow to limit
                                          visibilty to 500 feet or less for 3
                                          straight hours.
A Severe blizzard has winds over 72 mph, visibility practically
nothing and temperatures of below 10 degrees F.

Blizzards don't even need large snow fall, instead, winds can blow
up snow allready on the ground and cause a blizzard. This happens
a lot in antartica.
It may be supprising, but blizzards can cause massive amounts of damage.
They block all means of transportation, and sometimes block people inside
things. The snow weighs alot so the snow causes roofs to collapse, trees to
fall, powerlines to break, water pipes to shatter. Etc. All those effects happen
after the blizzard. Blizzards can be very supprising, and therefore cetch
people off guard. They can make people lost, not able to find their way, and
freeze. They can make whiteouts (either when the snow is so thick, you cant
see, or when the sun reflects off the snow), and cause car accidents.
Three things are needed to make a blizzard.

1. Cold air (below freezing) is needed to make snow.
 For snow to fall to the
ground, the temperature must be cold both up in the clouds where snowflakes
form, and down at ground level. If the air near ground level is too warm, the snow
will melt on its way down, changing to rain or freezing rain.

2. Moisture is needed to form clouds and precipitation. 
 Moisture in the air is
called water vapor. Air blowing across a body of water, such as a large lake or
the ocean, is an excellent source of water vapor. As wind moves air over the
water, some water evaporates from the surface, putting vapor into the air. This is
how “lake effect snowstorms” and “Nor’easters” pick up so much moisture.
However, cold air is not able to hold much water vapor. In fact, very cold air does
not make very much snow.

3. Warm, rising air is needed to form clouds and cause precipitation. 
 For a
blizzard to form, warm air must rise over cold air. There are two ways that this
may happen. Winds pull cold air toward the equator from the poles and bring
warm air toward the poles from the equator. When warm air and cold air are
brought together, a front is formed and precipitation occurs. Warm air can also
rise to form clouds and blizzard snows as it flows up a mountainside.

What Are Snowflakes?

Snowflakes are made of ice crystals. Each snowflake is made of as many as 200
ice crystals.

Some snow crystals are symmetrical, like the type that you cut from paper. They
form a hexagonal shape because that is how water molecules organize
themselves as they freeze. Others are small and irregularly shaped. If they spin
like tops as they fall to the ground, they may be perfectly symmetrical when they
hit the Earth. But if they fall sideways, they will end up lopsided.

Even though most have a hexagonal structure, there are so many ways that
water molecules can arrange themselves as the water freezes, that some people
say that there are no two snowflakes alike. Probably no two snowflakes have
exactly the same arrangement of molecules. But they can look alike. Many snow
crystals are like the two in the photograph below. They are simple in shape and
look alike.
 How Snowflakes Form

Snowflakes form in clouds where the temperature is below freezing (0ºC, or
32ºF). The ice crystals form around tiny bits of dirt that have been carried up into
the atmosphere by the wind. As the snow crystals grow, they become heavier
and fall toward Earth. Different types of snowflakes form in different conditions.
Temperature determines if the crystals become a flat plate, a long column, or a
prism shape.

On average, 10 inches of snow melt down to about an inch of water; however,
not all snow is the same. Some places receive very heavy snow. For instance,
only five and a half inches of January snow on Mount Washington, New
Hampshire, melt down to an inch of water. In contrast, over 15 inches of January
snow at Crested Butte, Colorado, melt down to an inch of water.

Other Icy Precipitation

Snow is not the only type of ice that falls from the sky! Other types are described
below.

Graupel: Snowflakes that have become encrusted with ice. This happens when
snowflakes pass through a chilly cloud on their way down and water droplets
freeze on them.

Ice pellets: Frozen raindrops, also known as sleet. They are usually quite small
in size and unlike snowflakes, do not have a crystal shape.


Hail: A frozen raindrop or graupel that is kept from falling to the ground by the
upward flowing air of a thunderstorm. The more droplets that freeze onto the
hailstone, the longer the hailstone spends in the sky. When it finally grows too
heavy to be held up by the flowing air, it falls to the ground.

				
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Description: Guide teaches you how do blizzards form