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What is a blizzard?

Blizzards are severe winter storms that pack a combination of blowing snow and wind resulting in very low visibilities.  While heavy snowfalls and severe cold often accompany blizzards, they are not required.  Sometimes strong winds pick up snow that has already fallen, creating a blizzard.  Officially, the National Weather Service defines a blizzard as large amounts of falling OR blowing snow with winds in excess of 35 mph and visibilities of less than 1/4 of a mile for an extended period of time (greater than 3 hours). When these conditions are expected, the National Weather Service may issue a "Blizzard Warning".   When a less severe, but still dangerous, winter storm is expected a "Winter storm Watch" or "Winter storm Warning" may be issued.  A "Winter storm Watch" is issued in advance and means that there is the possibility of a winter storm affecting your area. Keep alert and stay tuned to TV, radio, and other sources of weather information.  A "Winter storm Warning" means a winter storm is imminent or already occurring.



Blizzards can create a variety of dangerous conditions.  Traveling by automobile can become difficult or even impossible due to "whiteout" conditions and drifting snow. If you must drive in a blizzard, be prepared!  Make sure your automobile is properly equipped and that you have emergency supplies in case you become stranded or lost.



    Stay inside. When using ALTERNATIVE HEAT from a fireplace, wood stove, space heater, etc.:

    • use fire safeguards.
    • properly ventilate.

    No heat:

    • close off unneeded rooms.
    • stuff towels or rags in cracks under doors.
    • cover windows at night.

    Eat and drink.  Food provides the body with energy for producing its own heat.  Keep the body replenished with fluids to prevent dehydration.   Wear layers of loose-fitting, lightweight, warm clothing.  Remove layers to avoid overheating, perspiration, and subsequent chill.


Winter Deaths

Everyone is potentially at risk during winter storms.  The actual threat to you depends on your specific situation.  Recent observations indicate the following:

  • Related to ice and snow:
    • About 70% occur in automobiles.
    • About 25% are people caught out in the storm.
    • Majority are males over 40 years old.
  • Related to exposure to cold:
    • 50% are people over 60 years old.
    • Over 75% are males.
    • About 20% occur in the home.
    • How We Lose Heat to the Environment

      How we lose heat

    • Radiation - loss of heat to the environment due to the temperature gradient (this occurs only as long as the ambient temperature is below 98.6). Factors important in radiant heat loss are the surface area and the temperature gradient.
  • Conduction - through direct contact between objects, molecular transference of heat energy.  Water conducts heat away from the body 25 times faster than air because it has a greater density (therefore a greater heat capacity).  Stay dry = stay alive!  Steel conducts heat away faster than water.

Example: Generally conductive heat loss accounts for only about 2% of overall loss. However, with wet clothes the loss is increased five times.

  • Convection - is a process of conduction where one of the objects is in motion. Molecules against the surface are heated, move away, and are replaced by new molecules which are also heated. The rate of convective heat loss depends on the density of the moving substance (water convection occurs more quickly than air convection) and the velocity of the moving substance.
  • Wind Chill - is an example of the effects of air convection, the wind chill table gives a reading of the amount of heat lost to the environment relative to a still air temperature.
  • Evaporation - heat loss from converting water from a liquid to a gas
    • Perspiration - evaporation of water to remove excess heat
      • Sweating - body response to remove excess heat
      • Insensible Perspiration - body sweats to maintain humidity level of 70% next to skin - particularly in a cold, dry environment you can lose a great deal of moisture this way
      • Respiration - air is heated as it enters the lungs and is exhaled with an extremely high moisture content
      • It is important to recognize the strong connection between fluid levels, fluid loss, and heat loss. As body moisture is lost through the various evaporative processes the overall circulating volume is reduced which can lead to dehydration. This decrease in fluid level makes the body more susceptible to hypothermia and other cold injuries.
    • Winter Regions

      From the Mid-Atlantic Coast to New England...The classic storm is called a Nor'easter.  A low pressure area off the Carolina coast strengthens and moves north.  Wind-driven waves batter the coast from Virginia to Maine, causing flooding and severe beach erosion.  The storm taps the Atlantic's moisture-supply and dumps heavy snow over a densely populated region. The snow and wind may combine into blizzard conditions and form deep drifts paralyzing the region.  Ice storms are also a problem. Mountains, such as the Appalachians, act as a barrier to cold air trapping it in the valleys and adjacent low elevations.  Warm air and moisture moves over the cold, trapped air.  Rain falls from the warm layer onto a cold surface below becoming ice.

      Along the Gulf Coast and Southeast...This region is generally unaccustomed to snow, ice, and freezing temperatures.  Once in a while, cold air penetrates south across Texas and Florida, into the Gulf of Mexico.  Temperatures fall below freezing, killing tender vegetation, such as flowering plants and the citrus fruit crop.  Wet snow and ice rapidly accumulate on trees with leaves, causing the branches to snap under the load.  Motorists are generally unaccustomed to driving on slick roads and traffic accidents increase.  Some buildings are poorly insulated or lack heat altogether.  Local municipalities may not have available snow removal equipment or treatments, such as sand or salt, for icy roads.

      In the Midwest and Plains...Storms tend to develop over southeast Colorado in the lee of the Rockies.  These storms move east or northeast and use both the southward plunge of cold air from Canada and the northward flow of moisture from the Gulf of Mexico to produce heavy snow and sometimes blizzard conditions.  Other storms affecting the Midwest and Plains intensify in the lee of the Canadian Rockies and move southeast.  Arctic air is drawn from the north and moves south across the Plains and Great Lakes.  Wind and cold sometimes combine to cause wind chill temperatures as lo was 70F below zero.  The wind crosses the lakes, tapping its moisture and forming snow squalls and narrow heavy snow bands.  This is called "lake-effect snow."

      From the Rockies to the West Coast...Strong storms crossing the North Pacific sometimes slam into the coast from California to Washington.  The vast Pacific provides an unlimited source of moisture for the storm.  If cold enough, snow falls over Washington and Oregon and sometimes even in California.  As the moisture rises into the mountains, heavy snow closes the mountain passes and can cause avalanches.  The cold air from the north has to filter through mountain canyons into the basins and valleys to the south.  If the cold air is deep enough, it can spill over the mountain ridge. As the air funnels through canyons and over ridges, wind speeds can reach 100 mph, damaging roofs and taking down power and telephone lines.  Combining these winds with snow results in a blizzard.

      In Alaska...Wind-driven waves from intense storms crossing the Bering Sea produce coastal flooding and can drive large chunks of sea ice inland destroying buildings near the shore. High winds, especially across Alaska's Arctic coast, can combine with loose snow to produce a blinding blizzard and wind chill temperatures to 90F below zero!  Extreme cold (-40F to -60F) and ice fog may last a week at a time.  Heavy snow can impact the interior and is common along the southern coast.  With only brief glimpses of the winter sun across the southern horizon, the snow accumulates through the winter months.  In the mountains, it builds glaciers, but the heavy snow accumulations can also cause avalanches or collapse roofs of buildings.  A quick thaw means certain flooding.  Ice jams on rivers can also cause substantial flooding
    • Wind_Chill_Chart.gif (29396 bytes)
    • the Great Snow of 1717



    •  Some of the Biggest Blizzards Ever


      Some of The Biggest BLizzards are ...


      - 1888 March 11-14 in the eastern U.S...400 people died

      - 1940 November 11-12 Widwest u.s...144 people died

      - 1956 Feb. 1-29 West Europe ...1,000 people died

      - 1958 Feb. 15-16 North Eastern U.S ...171 people died

      - 1967 Dec. 12-20 South west U.S ...51 people died

      - 1988 in New York ... 400 people died

      - 1993 March 13-14 Eastern U.S ...200 people died

      - 1996 Jan. 7-8 Northeastern U.S... 100 people died

      - 1996 Aug. 22 Himalayas India ...239 people died










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