Prevention & Recovery

Decoding the Canadian weather forecast

Author: Canadian Living

Prevention & Recovery

Decoding the Canadian weather forecast

This story was originally titled "The Weather Report" in the December 2008 issue. Subscribe to Canadian Living today and never miss an issue!

"This is the true north strong and free, and cold and wet and icy and dark – sometimes all at once. It's why God invented long johns. This is Canada. We have winter. Life sucks. Get a toque. And embrace it." – Rick Mercer

How do you get prepared for winter? Share your tips for keeping safe and warm with other readers in the comments section below!

While we don't always laugh about winter, we certainly are fascinated by it. Here's how to understand our coolest season and get through it safely.

You say it's bitter, I say it's better
The first thing we've got to realize is that there's no such thing as a "Canadian winter." There are huge climate variations in this country, says Geoff Coulson, a warning preparedness meteorologist at Environment Canada. In Regina, for example, winter is characterized by blizzards and bitter windchill, while in Windsor, Ont., heavy rain is as much a part of winter as snow. In recognition of this fact, Environment Canada uses similar terminology across the country to describe a weather event (see "Winter weather words," pages 5 and 6), but allows flexibility in the criteria each region uses. For instance, since the west coast of B.C. doesn't see a lot of snow, an accumulation of about 10 centimetres in 24 hours or less may trigger a snowfall warning, whereas southern Ontarians don't get a warning until a total of 15 centimetres of snow falls within 12 hours.

The brr factors

Typically, winter weather systems in Canada originate in the west and southwest and move east, dragging with them bitterly cold arctic air. These low-pressure systems (see "Winter weather systems," page 6) are steered across the continent from the U.S. by the jet stream, a river of air high in the atmosphere. The greater the temperature differences between the sultry air to the south and the cold to the north, the stronger and faster the jet stream flows. Not surprisingly, the jet stream is most intense in winter.

Other factors that help determine the climate of a region include the amount of sunshine an area receives, its altitude and the presence of large bodies of open water. "Very cold air that passes over the open waters of the Great Lakes will be warmed, which has a moderating effect on the winter climate of southern Ontario," says Coulson.

In Winnipeg, on the other hand, "the nearby lakes [lakes Winnipeg and Manitoba] freeze up relatively quickly, so they have no mitigating effect on the polar express of air that comes down from Nunavut."

Be prepared
Here's what you can do to prevent becoming a winter weather casualty.
• Check the weather forecast. If a blizzard or other storm is predicted, stay somewhere safe and wait it out.

• Keep a supply of ready-to-eat, high energy food on hand, enough to last at least 72 hours, as well as a windup or battery-powered flashlight and radio. If you live in a remote area, you might want to prepare for a longer period of self-sufficiency.

• Ensure that you are able to heat at least one room of your home to 20 C. This may mean using a portable generator or an emergency heating unit such as a kerosene heater. Follow all operating instructions and be aware of the danger of carbon monoxide poisoning. Never use barbecues or camping stoves indoors.

Page 1 of 6 on page 2, find out the best ways to brave the winter weather!
If you're heading out
• If you live in a rural area and must venture out during a storm, make sure you don't get lost. Carry a compass and learn to use it before a storm hits. For going a short distance, tie a rope around your waist and securely fasten the other end to your home.

• Dress warmly and in layers. Wear a hat, since you lose the greatest amount of body heat through your head. Wrap a scarf around your face, and wear warm mittens or gloves and insulated waterproof boots with good treads.

• Cold weather strains your body, increasing your metabolic rate to help you produce heat. This metabolic rise can be hard on the heart, since it increases your blood pressure and heart rate. So take it easy. Since overexertion can kill, be careful when you're shovelling snow. Break up the task into manageable sections. Work slowly and take frequent rests; if you experience chest pain, stop immediately and get help.

• Ask your pharmacist if your medication can increase your vulnerability to cold temperatures; for instance, blood-pressure medications, beta-blockers and certain drugs for diabetes can make you more susceptible to cold.

• Watch out for icy patches; be especially careful on steps and driveways.

• Wind can lower air temperature and increase your rate of heat loss, so monitor the windchill as well as the temperature and dress appropriately.

Avoid frostbite
Frostbite occurs when you are exposed to temperatures below the freezing point of skin, and your tissues freeze. Your extremities – ears, nose, fingers and toes – are especially vulnerable.

There are two main types of frostbite. The superficial type affects the skin; deep frostbite can affect joints, bones and tendons, and lead to limb loss.

Being unable or unwilling to get in from the cold is the main reason people get frostbite. Especially high-risk situations include leaving skin exposed; wearing clothing that's too tight, is damp or not warm enough in temperatures of –15 C or colder; having a car accident or breakdown in bad weather; and drinking alcohol or using recreational drugs outside in the cold.

Smokers and people with diseases of the blood vessels are also at increased risk because they already have a decreased amount of blood flowing to their arms and legs.

Since there is no pain in the early stages of frostbite, learn to recognize these warning signs.

Your skin may:

• feel numb or look flushed;
• turn white or grey;
• tingle or burn; or
• feel cold to the touch.

If you suspect frostbite:
• Get yourself or the affected person to a warm area.
• Warm the frostbitten skin gradually by placing a warm hand on it or blowing on it.
• Never apply direct heat, such as a heating pad; it can burn the skin.
• Never rub the affected area.
• Seek medical attention as soon as possible.

Hypothermia

Prolonged exposure to cold temperatures can cause hypothermia – a condition in which the body loses heat faster than it produces it, causing the core body temperature to drop below 35 C. When this happens, body processes slow down. Symptoms requiring immediate attention are confusion, slurred speech, stiff muscles and uncontrollable shivering.

Risks for hypothermia, along with cold temperatures, include hunger, fatigue, dehydration and wearing clothes that are too tight, wet or inadequate for the conditions.

Page 2 of 6 – Go to page 3 for winter driving tips!
Winter wheels
Get a car checkup, which should include the ignition system, exhaust, wipers, heater and defroster, radiator, battery, belts, hoses, brakes and lights.

Install winter tires; look for ones marked with a pictograph of a snowflake inside a mountain peak. They're made with special rubber compounds and treads, and provide considerably better traction, braking and handling than all-season tires when the temperature falls below –8 C, even when roads are clear of snow. Winter tires are mandatory in Quebec.

• Never mix tires of different tread, size and construction; this will result in unsafe vehicle handling.

• Tell someone where you're going, your route, time of departure and when you expect to arrive.

• Travel on main roads and highways as much as possible.

Safe driving practices in snow, sleet and ice
• Slow down.

• Leave plenty of distance between your car and the vehicle ahead.

• Slow down when approaching bridges, overpasses and shaded areas; these spots freeze more quickly and will stay frozen longer than neighbouring areas.

• Beware of stretches of road that are black and shiny with frost or ice; this condition can cause your car to lose traction. When you experience such stretches, approach slowly, take your foot off the brake and shift into neutral.

• Avoid sudden braking and acceleration, and jerking the steering wheel, which can cause skidding.

• If you are in a skid, look where you want to go and steer toward that spot.

• If you're on ice and skidding in a straight line, shift into neutral or step on the clutch, and keep your foot off the brake.

• Keep your gas tank full. You don't want to run out of gas any time of year, but especially not in winter.

• Avoid driving in conditions of poor visibility. If you're on the road in such conditions, turn on your bright lights to be more visible.

• Turn back or seek refuge if driving conditions make you uncomfortable.

• Carry a winter survival kit in your car. In a perfect world, this would include a shovel, sand or other traction aid, towrope or chain, flashlight, batteries, warning light or road flares, extra clothing, blankets, emergency food pack (nutrition bars, chocolate, sport drinks), axe, booster cables, ice scraper, brush, gas-line antifreeze, road maps, a first-aid kit (which would include bandages, analgesics such as acetylsalicylic acid, and any medicines essential to your health), 50-hour candles, waterproof matches, a fire extinguisher and a cell phone.

Page 3 of 6 – Page 4 shows you how to keep your kids safe.

When you're stuck in a storm
You're in the car, and your planned one-hour trip has turned into a white hell: visibility is near zero, drifts of snow have hemmed you in, and you're not going anywhere – for hours at least. What to do?

• Don't panic. Stay in the shelter of your car and wait for rescue.

• Run the motor sparingly, for only as long as it takes to keep the cold at bay. To avoid carbon monoxide poisoning, occasionally check to ensure the exhaust pipe is not blocked.

• Open a window periodically on the side away from the wind to get an adequate supply of fresh air.

• Keep moving your hands, arms and feet.

• Don't fall asleep.

• Keep an eye open for assistance.

If you have a cellphone and are in a serviced area, dial 911 and speak to emergency services. Tell them where you are, your name, the names of any passengers, your licence plate number, the length of time you've been stranded, and inform them of any medical issues they should be aware of. Set a time to call again. To conserve your battery, do not make unnecessary calls.

Kids and cold

Check the forecast before ushering your children out the door. Don't let them out if extreme weather, such as a blizzard or ice storm, is called for.

Kids are more susceptible to frostbite and hypothermia, so don't let them stay outdoors long when the temperature (with or without windchill) reaches –15 C or colder. When it drops to –25 C, keep them indoors.

Make sure they're dressed in layers, with minimal exposed skin. Outerwear should include insulated winter boots, a winter coat and pants or a snowsuit, a hat, mittens, and a neck warmer instead of a scarf, which can get caught or tangled and choke a child.

On bright days, use sun protection. Reflections off snow and ice can increase the intensity of the sun's rays.

Give your kids plenty of warm fluids, such as cocoa, at regular intervals, since dehydration is a danger. To keep their internal central heating systems going, provide them with a nutritious meal before they head out, and give them some snacks, such as raisins and nuts, to take along.

Teach your kids to head for home or a warm shelter if their clothes get wet. Make sure they know it's OK to come indoors when they've had their fill of winter fun. Fatigue can lead to accidents and injuries.

Know where your kids are going and with whom, and tell them what time you expect them home.

Page 4 of 6 Go to the next page to learn about weather alerts.
Understanding basic weather alerts
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.
Snow squalls (or lake-effect snow): Occur when cold air passes over large bodies of relatively warm water, picking up moisture. As this air mass moves inland, it may snow heavily for a few hours in a localized area. May appear as if snow is falling from out of a blue sky. A warning is issued for regions downwind of the Great Lakes when at least 15 centimetres of snow is expected within 12 hours.

Snowfall: Warnings are given 12 to 24 hours in advance of hazardous amounts of snow expected over a 12- to 24-hour period. The definition of "hazardous" varies across the country, from five centimetres for parts of southwestern B.C. to 24 centimetres elsewhere.

Windchill: The way your skin feels when low temperatures combine with the effects of wind to blow away the thin layer of warmer air close to your skin. Warning criteria range from –55 C in some Arctic regions to –30 C in southwestern Ontario. Stay indoors. You risk frostbite in less than 10 minutes when the windchill is –40 C.

Winter storm:
Involves more than one winter hazard and may include heavy snow, reduced visibility, strong winds and freezing rain.

Winter weather systems

Alberta clipper: A fast-moving (50 to 60 kilometres per hour) low-pressure system that moves from the Prairies to south of the Great Lakes and over the New England states. It brings significant snowfall to southern Ontario and southern Quebec.

Colorado low:
Born in the foothills of Colorado's Rockies, this system carries moisture from the Gulf of Mexico to Eastern Canada. It produces big snowfalls, freezing rain and heavy rain.

East coast low:
A system that moves up the eastern seaboard of the U.S. and into the Maritimes and eastern Quebec, resulting in snow and freezing rain.

Gulf low: A system from the Gulf of Mexico that tends to move almost due north into southern Ontario, bringing lots of snow, freezing rain or rain.

Weather info 
Environment Canada's website is one of the best sources for up-to-the-minute weather news. Weather information is broadcast 24 hours a day across the country. You can receive it over family radio service and general mobile radio service, two way radios intended for short-distance personal communications.

The Weather Network and other private-sector providers also offer weather warnings on television and online, and for a fee you can receive a text message on your cell phone.


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