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 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 area also a problem. Mountains, such as the Appalachian, 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 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 of 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 northwest 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 low as 70 F 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 over 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, windspeeds 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 drive large chunks of sea ice inland destroying buildings near the shore. High winds, especially across the Alaska's Arctic coast, can combine with loose snow to produce a blinding blizzard and wind chill temperatures to 90F below zero! Extreme cold (-40 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. Ice jams on rivers can also cause substantial flooding.