Special weather statements are issued for events that are unusual, cause general inconvenience or concern, and cannot be adequately described in a weather forecast. For instance, statements may be used to alert the public to conditions of reduced visibility as a result of fog or blowing snow.
WATCHES are a "heads-up" that conditions are favourable for a storm. Since forecasters can see storms on radar as they develop in the American southwest, the U.S. Gulf Coast and the Canadian Prairies, they may issue a winter watch as many as 30 hours in advance of the anticipated event. Because a storm's path is unpredictable, a watch is issued for a broad area, and frequently updated.
WARNINGS alert you to severe weather that is occurring or is imminent. In winter, imminent means six to eight hours before the freezing rain starts or snow falls. Because the time lag is shorter, warnings cover a much smaller area than watches, which means meteorologists have a better idea of who is going to be hit, with what and in what amount.
Winter weather words
Arctic outflow (locally called a squamish): Cold air from the Pacific Ocean that travels inland to the B.C. interior, then flows through gaps in the mountains, bringing gale-force winds, unusually cold temperatures, heavy snowfall and severe ice to coastal regions.
Blizzard: A combination of strong winds and falling or loose snow that reduces visibility. Whiteouts are common. Warnings are issued 12 to 24 hours in advance of anticipated winds of 40 kilometres per hour or more in snowy conditions that are expected to reduce visibility to less than one kilometre for at least four hours.
Blowing snow: If it's expected that visibility will be reduced to less than one kilometre, but other conditions do not meet the definition of a blizzard, a warning or special weather statement may be issued.
Chinook: A wind that comes down the eastern slopes of the foothills of the Rockies, causing rapid warming. Calgary, for instance, can experience a 30-degree rise in temperature in a few hours, from –15 C to 15 C.
Flash freeze: Occurs when the temperature drops rapidly, within two to three hours, from above freezing to below 0 C, and surfaces are wet. A local warning may be issued.
Freezing drizzle: Drizzle or light rain that freezes on impact at temperatures below 0 C. Causes slippery conditions. Does not build up to the same extent as freezing rain. Warnings are issued when a significant accumulation is anticipated or, in the Maritimes, when this condition is expected to last at least seven hours or, in Newfoundland and Labrador, when the condition is expected to last eight hours or more.
Freezing rain: Rain that freezes on contact to form a coating of ice on roads, sidewalks, overhead wires and tree branches. Can build up to a dangerous thickness. Warnings are issued when one to four hours or at least two millimetres of freezing rain is expected.
Page 5 of 6 – Go to page 6 for more winter weather words.
