Expected heavy rainfall in Vancouver increases risk of flash flooding, Environment Canada warns

Environment Canada has issued a special weather statement for the Metro Vancouver area, warning that heavy rainfall in the region over several days increases the risk of flash flooding.

Environment Canada said in the statement on Friday that a “major change” in the weather pattern is in the works. “The high pressure system that has trapped wildfire smoke over Southern B.C. will finally shift east thanks to a pair of incoming storms,” the statement said. “The storms will merge two jet streams into a single river of sub-tropical moisture that will bathe the South Coast with the first significant rainfall in months.”

Weather models are indicating 80 to 120 millimetres (mm) of rain over the South Coast between Friday night and Monday morning. About 20 to 30 mm of rain is expected to carry over into the mountainous regions of the Interior during the same period.

Due to the drought conditions over these regions, the soil has a reduced capacity to absorb water, Environment Canada explained. “Heavy rainfall thus increases the risk of flash flooding. Additionally, given the recent prolonged dry period, road surfaces may become slippery resulting in poor driving conditions.”

To mitigate the risk of flash flooding, Environment Canada recommends ensuring drain spouts and sewer covers are free of debris, so water can freely drain. The agency also recommended people avoid roadway underpasses, drainage ditches, low lying areas and water collection areas during heavy rains, as they can unexpectedly flood or overflow.

Motorists also should not drive across a flooded road, as it can be difficult to tell the condition of the road under the water.

Vancouver expecting get a summer’s worth of rain in just one weekend #cbcnn pic.twitter.com/CDmZWCjqlo

— CBC Morning Show (@CBCMorningShow) August 28, 2015