Blizzards and winter storms can be more dangerous than summer storms. America’s worst winter weather comes from blizzards, which can be generated by specific conditions in the upper Midwest and by nor’easters on the east coast. Other regions of the US are seldom hit. The National Weather Service issues a blizzard warning when it projects that visibility will be less than a quarter mile due to sustained winds in excess of 35 mph blowing snow. The amount of snowfall matters not. A blizzard is considered severe after it develops 45 mph sustained winds.
Every year, blizzards cause tens of millions of dollars in property damage. Their speedy, blisteringly chilly winds can quickly deliver feet of snow, freeze livestock, stagnate traffic, shut down commerce and quickly cause frostbite and hypothermia. The wind chill temperature index combines the effects of blowing winds with bitterly cold temperatures to describe how weather actually feels. Blizzards in the northern states have been known to deliver wind chills of -60°F. What is not included in the index are the effects of snow sticking to skin, melting and then evaporating. The two physical changes require latent heat, which is leached from the body.
Historically, the most dangerous blizzards are those which develop suddenly and intensify dramatically, which strengthens winds and delivers more snow. Many blizzards have taken the lives of hundreds. About 3,000 soldiers traveling on foot perished during a 1719 Norwegian and Swedish blizzard during what’s now called the Carolean Death March. In 1972, Iran was surprised by a week-long one that killed about 4,000.
Aircraft must avoid blizzards. Added weight from the quick accumulation of freezing precipitation can alter the aerodynamics of their wings and hinder flight. They also need to be freed of snow and ice before they’re cleared to depart. Sustained heavy snow requires lots of runway plowing, which delays flights. If aircraft can’t gain sufficient traction, they can’t land or take off.
Photo is satellite view of a 2010 blizzard. Image courtesy of NASA.
Written by Meteorologist Geoff Linsley