Ground blizzards are extremely dangerous because they are preceded by unseasonably warm air, which can cause people to let their guard down. People may venture outside without proper winter clothing. This relatively warm weather does not last long. The ground blizzard occurs when an Arctic cold front moves through the region, causing temperatures to drop and winds to increase, often reaching gusts of 50 to 60 mph. If there are several inches of deep fresh snow on the ground, this strong wind will quickly pick up the snow and create whiteout conditions. Another reason these blizzards are dangerous is the cold temperatures that follow behind the Arctic front. Anyone stranded in their vehicle or forced to walk outside is at risk of frostbite or hypothermia.
Ground blizzard refers to a weather condition where loose snow or ice on the ground is lifted and blown by strong winds. The primary difference between a ground blizzard and a regular blizzard is that in a ground blizzard no precipitation is produced at the time, but rather all the precipitation is already present in the form of snow or ice at the surface.
While the term “ground blizzard” is often associated with intense blowing and drifting snow conditions, there are specific criteria which must be met. Often such criteria will be determined by a country’s governing weather agency or other similar body. In the U.S, according to the National Weather Service a blizzard is defined as having sustained winds or frequent gusts of 35 mph or more, visibility frequently below 1/4 mile in considerable snow and/or blowing snow, and the above conditions are expected to prevail for 3 hours or longer. Environment Canada similarly maintains that the temperature must be colder than 0°C, widespread reduction of visibility to less than 1 kilometer due to snow and/or blowing snow and sustained wind speeds or gusts of 40 km/h or more, with all these conditions persisting for at least 4 hours (6 hours for the Northwest Territories and Nunavut)
There are 3 different forms of ground blizzards:
- In horizontal advection conditions, the winds blow across the surface of the
earth with very little if any large-scale upward motion.
- In vertical advection conditions, the winds exhibit large-scale upward
motion lifting the snow into the atmosphere creating drifting waves of snow
up to 500 meters in height.
- In thermal-mechanical mixing conditions, massive convective rolls form in
the atmosphere and the blizzard may be observed from space with the
blizzards convective rolls creating waves of snow (also known as snow
billows) resembling lake or ocean effect snow bands. The extreme conditions
can quickly bury a two story home and make breathing very difficult if not
impossible if caught outdoors.
Ground blizzards occur throughout the world, however unlike other winter storms, topography either aids in their formation or prevention. The most important topographic element in a blizzard is the requirement for a vast amount of large open and relatively flat land. Any type of flora, especially coniferous forms, will catch any drifting snow significantly reducing the blizzards effects. The environment must also support temperatures cold enough to prevent any snow on the ground from melting and bonding the ice crystals together.
Ground blizzards are most common in the Arctic and Antarctic during seasonal transition periods, such as the spring and fall. Ground blizzards are also common in the Canadian Prairies and U.S Midwest as well as Siberia and Northern China.
The White Hurricane of 1977-1978
The blizzard of 1977 hit Western New York as well as Southern Ontario from January 28 to February 1. Daily peak wind gusts ranging from 46 to 69 mph (74 to 111 km/h) were recorded by the National Weather Service in Buffalo, with snowfall as high as 100 in (254 cm) recorded in areas, and the high winds blew this into drifts of 30 to 40 ft (9 to 12 m). There were 23 total storm-related deaths in western New York, with five more in northern New York.
Certain pre-existing weather conditions exacerbated the blizzard’s effects. November, December and January average temperatures were much below normal. Lake Erie froze over by December 14, 1976; when that happens lake-effect snow does not occur because the wind cannot pick up moisture from the lake’s surface, convert the moisture to snow and then dump it when the winds reach shore.
Lake Erie was covered by a deep, powdery snow; January’s unusually cold conditions limited the usual thawing and refreezing, so the snow on the frozen lake remained powdery. The drifted snow on roadways was difficult to clear because the strong wind packed the snow solidly. In addition to the roads becoming impassable, motorists had to deal with vehicles breaking down due to the combination of very cold temperatures, very high winds and blowing snow.
In the hardest-struck areas, snowmobiles became the only viable method of transportation. In Western New York and southern Ontario, snow which was accumulated on frozen Lake Erie and snow on the ground at the start of the blizzard provided ample material for the high winds to blow into huge drifts. The combination of bitter cold, high winds, and blowing snow paralyzed areas affected by the storm. Lake Ontario rarely freezes over, which meant northern New York had to deal with considerable lake effect snow. Coupled with the existing snow cover and wind, this had a similar effect.
Weather conditions during the months leading up to the blizzard allowed the blizzard to have the
impacts it did. A high-amplitude planetary wave pattern set up, which was very persistent from October 1976 through January 1977, and involved a ridge over western North America and a trough over eastern North America. In January 1977, this pattern persisted, with the pressure of the strong ridge over western North America being more than two standard deviations from the mean, while the strong trough centered over eastern North America was more than three standard deviations from the mean.
A strong blocking high developed over the Arctic Ocean during January, and this moved the polar vortex to southern Canada, south of its normal location. Strong northwest flow between the ridge and the trough resulted in a strong northwest flow in between, which ushered Arctic air into the central and eastern United States. The circulation helped cause record cold for the winter over many portions of the eastern United States, with the Ohio Valley averaging more than 8 °F (4 °C) below normal. The severe winter was not limited to the northeastern United States; snow was observed in Miami, Florida, on January 20, and snow mixed with rain occurred in the Bahamas. In contrast,
Alaska was exceptionally mild: Anchorage averaged 20.2 °F or 11.2 °C above normal and was in fact 2.5 °F or 1.4 °C warmer for the month than Atlanta (half the distance from the equator), whilst it was the warmest January since at least 1937 for the whole state except the North Slope. The Pacific Northwest, located under the strong ridge, experienced unprecedented drought, with all twenty-nine climatic divisions of Washington, Oregon and Idaho experiencing their driest October to February period on record.