In February 2018, British Columbia’s South Coast confronted surprising amounts of snow, startling residents accustomed to the region’s calmer winter weather. Twenty centimetres of the fluffy white precipitation snarled traffic, closed schools and was followed quickly by another storm.
Winter weather can hit traditionally balmier Canadian locales, so it pays to understand warning types that Prediction Centres and local forecasters may broadcast ahead of frosty events across the territories and provinces. Weather services issue alerts for storms or weather conditions that could produce snow, sleet or freezing rain, helping to prepare residents for threats to property or lives. Meteorologists categorize these alerts into three levels of ascending danger.
A winter storm watch is the first level of warning. It signifies that conditions are favourable to produce winter weather: snow, sleet, freezing rain, icy roads and the like. These conditions may or may not occur, but the weather service is alerting residents to the possibility. During a watch, residents should seek further weather news at regular intervals.
A winter weather advisory is the second level of warning. It is issued when winter weather is likely to create a hazard. Generally, the weather service is expecting snow, sleet, freezing rain, icy roads and other dangerous conditions. Amounts sufficient to trigger an advisory rather than a winter storm warning vary from location to location. During advisories, residents should take precautions during outside activities or postpone them if possible.
A winter storm warning means that a winter storm is either expected soon or already taking place. Heavy snow, white-out blizzards, sleet, high winds and significant ice accumulations may be imminent, and residents should prepare immediately and take cover against deteriorating conditions. Depending on location, warnings may be triggered by less or more snow; flat locations prone to blowing and drifting could hear warnings if 10 centimetres are expected over 12 hours. Mountainous areas may not qualify unless 20 centimetres are forecast over 12 hours.
Keeping an eye on winter weather alerts is sound practice because it doesn’t take much moisture to add up to a significant snowfall. The equivalent of a hard thunderstorm in summer may produce mounds of dense snow that stymie travel and cause risk.