Figure 16.36: A near white out in a blizzard in Minnesota. ( 22 )the jet stream has traveled south and a cold, northern air mass comes into contact with
a warmer, semitropical air mass. The very strong winds develop because of the pressure
gradient between the low pressure storm and the higher pressure west of the storm. Snow
produced by the storm gets caught in the winds and blows nearly horizontally. Blizzards
can also produce sleet or freezing rain.
The snowiest, metropolitan areas in the United States are Buffalo and Rochester, New York.
These cities are prone to gettinglake-effect snow. While other locations can have lake
effect snow, the greatest amount is on the leeward side of the Great Lakes. In winter, a
continental polar air mass travels down from Canada. As the frigid air travels across one of
the Great Lakes, it warms and absorbs moisture. When the air mass reaches the leeward
side of the lake, it is very unstable and it drops tremendous amounts of snow. Buffalo is on
the leeward side of Lake Erie and Rochester is on the leeward side of Lake Ontario.
While lake effect snow is not a blizzard, the two can work together to create even greater
snows. The Great Lakes Blizzard of 1977 was created mostly by the passage of a cold front
over the area. The snowfall was aided by lake effect snow coming off of Lake Ontario, which
had not yet frozen that winter.
Extreme Heat and Drought
Although not technically storms, extreme heat and drought are important weather phenom-
ena. A heat wave is defined as extreme heat that lasts longer than normal for an area.
During a heat wave, a high pressure zone sits over an area and hot air at the ground is
trapped. A heat wave can occur because the position of the jet stream makes the area hotter
than it is normally. For example, if the jet stream is further north than usual, hot weather